missing pages - using a camera tutorial
TRANSCRIPT
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Missing Pages: ISO Setting
Tips for Using Your Camera Creatively by Jon Sienkiewicz
The Missing Pages column is a collection of all of the information that should have been included in your cameras Owners Manualbut somehow got left out. This is a hybrid assortment of short
articles that delivers the know-how you need to derive the maximum enjoymentand creative
expressionfrom your equipment. Its sort of a juiced-up User Guide for creative people who are
not necessarily technical. Each part will teach you how to use one of the camera features or
functions that you previously ignored or left set on Auto. And each will include a Creative Project so
that you can try some scripted experimentation.
We will explain complex technical subject matter a way that everyone can understand. And if you
happen to be a technical expert yourself, were including Nerds Only sidebars just for you. That
way you can dig in deepor just straddle the edgesof the technological stuff. Its your decision.
Installment I: ISO Setting
[also known as Sensitivity Setting or ISO Sensitivity]
Imaging sensors are designed to perform their best when light is at a
certain level. For the convenience of photographers who are accustomed
to understanding the different sensitivity levels of film, manufacturers
(for the most part) build sensors that have roughly the same sensitivity
as a roll of ISO 100 film. In an attempt to keep everything familiar and
understandable, camera makers use a numbering system thats closely
equivalent to the old ISO ratings from film photography. Some even refer
to the relative speeds as ISO, but thats technically not correct.
Nonetheless, for the sake of simplicity well do the same.
This sensitivity can be adjusted to accommodate lower light levels.
Increasing the sensitivity setting to ISO 200, for example, makes the sensor twice as sensitive.
Changing to ISO 400 makes it 4X as sensitive as 100. Increasing the ISO will allow you to shoot in
low light at a shutter speed thats fast enough to prevent camera shake. Thats the primary reason
why one would want to increase the ISO: to make it possible to shoot at a more desirable
combination of f/stop and shutter speed.
Cameras that offer image stabilization lower the shake threshold, so you might be able to shoot at,
say, 1/15th of a second instead of 1/60th. Thats a difference of two stops and the same as increasing
the ISO from 100 to 400. This gives you an idea of how important image stabilization is.
Increasing the ISO and keeping the shutter speed the same will allow you to shoot at a smaller lens
opening (f/stop). That will increase the depth-of-field and increase the zone of sharpness that
extends behind and in front of the point of focus.
Then why not always shoot at ISO 1600?
Adjusting the ISO changes how the camera responds to a given quantity of light. These increases
come at a price, however. As sensitivity increases, so does noise. Noise is the mottled, grainy-
looking texture that appears when you shoot at a high ISO.
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Nobody likes how noise looks, so camera makers use a countermeasure. They process the noisy
digital image signals with noise filters and noise suppression algorithms. This operation occurs in
the signal processing engine. Canon calls their engine DIGIC IV. Panasonic calls theirs VENUS.
Camera makers brand their engines for marketing purposes, and also to track generational
differences (DIGIC IV vs. DIGIC III, for example).
All camera makers handle noise suppression in their own way, so even if two brands of cameras use
the same sensor (which is very common) the results can be quite different because the engines are
different. The noise suppression process often reduces the image sharpness. This bears repeating:
noise suppression is the enemy of sharpness. So we can say that every low-light image is a
compromise between noise and sharpness.
But signal noise is only part of the equation (albeit the biggest part). Light level is also an important
variable. Many folks dont realize this, but shooting at a high ISO like 800 in bright light will yield
better results than shooting at a high ISO in near darkness. Dont misunderstandits always better
to use the lowest ISO that conditions allow. But its important to understand that noise is a product
of high ISO and low light. In some cases its better to shoot at ISO 400 in bright light than ISO 100
in the dark. Thats because noise can increase as a function of time, also. And lower ISO settings
require longer shutter speeds.
What about ISO 50?
Some camerasearly Canon PowerShots, for instancehave ISO 50 settings. Others have ISO 64 or
ISO 80. Settings lower than ISO 100 generally produce the best images a camera can makeat least
as far as noise is concerned.
Leaving your cameras ISO setting on Auto is a mistake. The camera could use a higher setting than
necessary and cause your image to appear grainy or noisy. You dont want that. Besides, you cannot
accurately control the aperture setting or shutter speed setting unless you also control the ISO
sensitivity.
Digital SLR cameras generally perform better than compact cameras at high ISO settings. This is
not always the case, and some compactsthe old Fujifilm Finepix F31 is a notable examplecan
hold their own even when photographing the legendary black cat in a coal bin at midnight. You
can read more about the technical reasons behind this in the Nerd section below.
Creative Project
You dont need any special equipment for this one, just your digital camera. If you happen to have a
lightweight tripod you can expand the project, but thats up to you.
Heres the drill. In normal daylight, photograph a colorful subject at every ISO setting your camera
offers starting at the lowest and working your way up to the highest. Shoot only one shot at each ISO
so that it will be easier to compare the results.
Repeat the same exercise indoors under ambient light that is just sufficient for reading. Dont worry
if the images shot at the lower ISO settings are blurrythats normal. If you want to do the indoor
portion on a tripod, thats fine.
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Depending on your camera, the actual light levels and the subject, you should find that noise
increases as ISO increases. In the outdoor shots, the effect will be less pronounced because there is
more light to saturate the photo sites. The indoor the images may get as shaggy looking as coconut
pancakesor look like a bad example of pointillism.
How does this help you creatively? You must learn to judge light levels and use the ISO setting that
will produce acceptable results. Different camera brand behave differently so its important to
understand how yours performs. Once youve mastered this sense for light levels youll know when
to use flash or a tripod.
Well say this now and doubtlessly repeat it throughout the Missing Pages series: creative
photography is about getting exactly what you wantits not about wanting whatever you get.
Nerds Only
ISO is an abbreviation for International Organization for Standardization. Yes, I know that should
make it IOS instead of ISO (but one must admire a standards organization thats willing to be abit unorthodox). Old timers may refer to the same specification as ASA, the more ethnocentric
American Standards Association. And our European cousins still recall the German counterpart:
DIN (Deutsches Institut fr Normung).
The digital noise that appears when a high ISO sensitivity setting is used is partly the result of
physical measurement between photo sites (pixels) that engineers call pitch. Pixels that are
packed very densely together have a very small pitch and are noisier.
At a given megapixel level, small imagers have greater density, smaller pitch and therefore more
noise. The image sensor (usually a CCD but sometimes CMOS) is measured diagonally and the
dimension is expressed as a fraction. To confuse you, the fraction contains a decimal in the
denominator. A CCD that is 1/2.5 inches is actually equal to 1 divided by 2.5 inches, or 0.40 inches. A CCD thats 1/1.6 (which may seem smaller) is 0.625 andall else being equalwill produce
images with less noise.
To really confuse the issue, many people refer to the ISO setting as the speed. This is another
throwback to 35mm photography where we often talked about film speed. Its best to avoid this
nomenclature since speed is already overused to describe large f/stops (fast, high-speed f1.2
lenses) and shutter speed. A better term for sensitivity adjustment, scientifically speaking, would
be gain. Audiophiles and people who dig shortwave radios are already familiar with this
expression as the technical term for an amplifiers output/input magnitude ratio.
You can remove most of the noise from a digital image during post processing by using NIK
Softwares Dfine or other product. Adobe Photoshop CS4 also has some potent noise-busting tools.But like poison ivy and hangovers, its always better to avoid noise than to cure it.
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Installment II: Program AE
[slightly more extensive than the auto/green mode]
Definition: an auto exposure system in which the camera achieves correct exposure by selecting the shutter
speed and aperture (f/stop) from a predetermined table.
To understand Program AE you must understand the fundamentals of exposure. The amount of light that
reaches the imaging sensor is determined by two physical factors: the size of the lens opening (aperture, or
f/stop) and the length of time the light is allowed to travel through that opening (the shutter speed). The
sensor doesnt care whether you use a small aperture for a long time or a large aperture for a short time, just
so long as the net result is that the same amount of light reaches it.
In other words, its possible to achieve exactly the same precisely correct exposure using different
combinations of apertures and shutter speeds. For example, you can shoot at f/2 at 1/500 second, or f/8 at
1/60 and either combination will yield correct exposure. However, which combination you choose can have a
profound effect on your image.
Please take a look at the accompanying graph. The red line shows Equivalent Exposure. Shooting at f/16 for
1/8 second is equivalent to f/5.6 at 1/60. The green line is called a Program Slope. It shows how a typical
Program AE system might automatically adjust shutter speed and f/stop settings in reaction to differing light
levels. With most cameras, the steps are seamless and infinitely variable but follow the same slopewhich
means you may shoot at 1/131 of a second at f/4, for instance. In this example, Program AE forces the camera
to use a high shutter speed as much as possible, and never drops below 1/60 of a second.
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Program AE makes rational choices for you. In general, Program AE tries to shoot at a relatively fast shutter speed
because it operates under the normally correct theory that most people have a hard time holding cameras still at
slower speeds. Program AE delivers correct exposure and good results most of the time. But when you use this
mode the camera is making two critical decisions for you, and whenever the camera is doing the decision making,
you are losing creative control.
Remember, your creative ambition is to get what you want, not merely want what you get.
Look at the image of the young girl holding a snail. The hand is in focus but the
girls face is blurred. The image was not shot in Program AE. It was shot at wide
open at f/2.8 to obscure the human and emphasize the creature.
If you want to control depth-of-field you must control the aperture. Small
apertures produce greater depth-of-field than large ones (all else
being equal). If you want to control subject motion (e.g., freeze action at a
sporting event) you must have control over the shutter speed. Slow speeds allow
subject blur whereas fast shutter speeds do not.
Camera manufacturers are aware that not every program setting meets the needs of the shooting
environment, photographers creative impulse and subjects special requirements. So they have provided two
effective ways to provide photographers with creative control. The first is called Program Shift.
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Installment III: Aperture & Shutter Priority
Definition: exposure modes that provide more control than Program AE but less
than Manual mode.
Shutter Priority is an auto exposure system in which the camera achieves correct exposure by selecting the
aperture after the user has selected the shutter speed.
Conversely, Aperture Priority is an auto exposure system in which the camera achieves correct exposure by
selecting the shutter speed after the user has selected the aperture.
Each system has its own set of distinct advantages and disadvantages. But to fully understand Aperture
Priority and Shutter Priority you must understand the fundamentals of exposure. Please refer to the preceding
segment (Program AE) if you need a quick review.
Todays digital SLR cameras (and a few high-end compact models like the Canon PowerShot G10) offer both
Aperture Priority and Shutter Priority automatic modes in addition to Program AE. There was a time,
however, back during the era of Canon AE-1 popularity, that 35mm film cameras offered one autoexposure
system or the other. And each method had its own passionate group of proponentsand detractors.
The Canon (Shutter Priority) crowd argued that it was better to set the cameras shutter speed and allow the
camera to respond by setting the appropriate f/stop. They claimedand rightfully sothat by choosing a fast
shutter speed it was easier to control camera shake and to stop subject movement. Minolta, Nikon and Pentax
(Aperture Priority) followers insisted that setting the aperture was the preferred procedure because it gave the
user full control over the depth-of-field and allowed the user to preselect the optimum aperture for any lens.
Both sides were correct, of course, each in their own way. In retrospect, this issue was one of the most
polarizing disputes among camera enthusiasts, no pun intended. One might have expected a different
outcome to this hotly debated argument, but the final result was the development of Program cameras that set
BOTH the shutter speed and aperture, essentially leaving the user out of the equation almost entirely. Better
cameras offered all three: A mode, S mode and Program AE. The Minolta XD-11, which debuted in 1977, was
the first camera that could claim Dual Mode by offering both A and S modes.
Aperture Priority
Sometimes called Aperture Preferred because that term more accurately
describes whats in the users mind when they make decisions about the
camera settings; and labeled Av (Aperture Value) by Canon and others;
Aperture Priority allows the user to control depth-of-field (that zone of
sharpness that extends in front of and behind the actual point of focus).
Because its often indicated by an A on the control dial, some people
mistake the setting for Automatic.
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Having control over the DOF is very important in more situations than not. When shooting portraits, for
example, its desirable to force the background to blur by using a large aperture. This effect separates the
subject from whats behind them and gives the appearance of accentuated sharpness. It also allows you to
deemphasize distracting backgrounds by making them fuzzy and indistinguishable. Controlling DOF is
similarly important when you want a larger zone in focus (greater DOF), such as when shooting close-ups or
certain landscape scenes.
Controlling the aperture allows you to select the sweet f/stop that delivers the sharpest images. There are
rare exceptions, but most lenses perform better when stopped down two or three f/stops. A 50mm f/1.4
Nikkor, for example, will yield better results at f/4 than it will at f/1.4. And contrary to intuitive logic, using an
f/stop like f/22 thats quite small introduces diffraction, which robs the image of sharpness, despite the
extended depth-of-field.
Shutter Priority
Known as Tv to Canon (for Time Value), theres a lot to be said about
the efficacy of this systemparticularly in light of the fact that all camera
makers recognize the detrimental effects of camera shake and are moving
toward some sort of Image Stabilization to reduce it.
In S Mode, you set the shutter speed and the camera does the rest. Well,
not quite. The argument that the Aperture Preferred crowd often made
was this: if you set a shutter speed thats too high (1/250s indoors, for example) youre likely to get no picture
at all. As a countermeasure, many cameras will warn you and then shift to a slower speed when its impossible
to achieve correct exposure at the speed you selected. And some will even adjust ISO (although thats really a
case of relinquishing control over the final outcome to the camera and hoping for the best).
Controlling the shutter speed means you can help prevent camera shake and more importantly, freeze subject
movement. If youre shooting a track and field event, for example, or a little league game, you can use a very
fast shutter speed to stop motion.
This theory works well indoors, too. For any given lens you should know the minimum shutter speed you can
successfully handhold without shake. I call this the SBA or Shake Begins At
shutter speed (ungrammatical but easy to remember). With a 50mm lens
equivalent, for example, most people can shoot at 1/60 of a sec or so. General rule
of thumb is 1 over the focal length as in the fraction 1/focal length. So the
equivalent to a 135mm lens would require a shutter speed of about 1/125 or higher
for safe, jiggle-free results. (Remember that this old rule came to be before digital,
so you must account for the lens multiplier when calculating.) In Shutter Priority
you can set the camera at your SBA and blaze away with little fear of camera
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shake.
Creative Project
Do you have a favorite lens? One that always seems to yield the sharpest images? With that go-to lens in mind,
what range of apertures delivers the absolute best performance? You really need to know. For the sake of
having an example, lets say youre a Nikon D90 shooter and your favorite lens is the 50mm f/1.4. (Not a bad
choice, by the way, in that it translates to a 75mm f/1.4 on your DSLR, which gives you a nearly perfect
portrait lens).
Exercise 1
Get out the tripod, find a subject with detailed texture, and set up ten to fifteen feet away. If you cant think of
anything better, aim your camera at a painting thats hanging on a neutral wall. Shift your camera into
Aperture Priority mode and begin shooting at the largest f/stop, working your way down to the smallest. How
do the images in the series compare in terms of sharpness?
You may find that your results resemble these: Wide open at f/1.4 you get good results, but stopped down to
f/4 or f/4.5 (the half stop between f/4 and f/5.6) the lens really shines. Sharpness remains until around f/16
where diffraction takes over and the resultswhile still acceptableare not as biting-sharp as at f/5.6 or f/8.
Exercise 2
For the second exercise, position a human subject five feet from the painting and ten feet from the camera.
Repeat the exercise above, keeping the camera focused on the human. This time when you examine the
results, closely look at how the subject becomes more separated from the background as depth-of-field
decreases.
Exercise 3
Dont freeze the action all of the time. Movement can add dramatic emphasis to the dynamic flow of a river,
for example. Youll need the tripod again. If you dont have a gushing waterfall handy, moving traffic
(especially at night), frenetic musicians (especially during the wee hours) or typical preschoolers (after a
sugary snack) will provide enough subject movement to make this test worthwhile. In S mode, select a very
slow shutter speedone-half second or longer, unless its so bright that youll overexpose. Make sequential
exposures at progressively faster speeds until you reach the speed that completely stops all subject movement.
Then compare the results in your favorite image editor.
What about M mode? M stands for Manual, of course. Thats a great Creative Project but thats for another
episode!
For Nerds Only
Whats Pi got to do with f/stops? And why is f/2 twice as big as f/2.8 and four times larger than f/4? Shouldnt
bigger numbers mean bigger apertures?
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Shutter speeds are pretty easy to understand. 1/100 of a second is obviously half as long as 1/50 of a second.
But when it comes to f/stops nothing seems to make sense. Thats because an f/stop is a fraction. Its the ratio
between the lenss focal length and the diameter of the active aperture. For example, a 50mm lens that is set at
f/2 has an aperture that is 25mm in diameter. Similarly, a 50mm lens that is set at an aperture that is 8.9mm
in diameter is said to be set at f/5.6 (i.e., 50/8.9 = 5.6).
Remember high school algebra? Im sure many photo.net readers will want to jump in here and untangle my
amateur math, but heres what I remember. To calculate the area of a circle one multiplies the radius times the
radius times pi. Or in other words, the radius squared multiplied by the constant 3.14159.
If youre still with me, look at the following table.
For a 50mm lens:
So, its (fairly) easy to see why f/2 is about twice as large as f/2.8. The area is about twice as large. As we go
down the scale, each increment of one f/stop equals a 2X change in exposure because the area becomes half as
large. That is to say, each subsequent f/stop is one-half as large as the preceding f/stop. Half of a half is a
quarter, so the difference between f/4 and f/8 is two stops, or 4X.
Why use such a goofy system? Because it can be applied to a lens of any focal length. For the purposes of
calculating exposure, a 135mm lens set at f/5.6 delivers exactly the same amount of light as a 300mm lens at
f/5.6. Were it not so, it would be virtually impossible to base camera exposure settings on an external
handheld light meter.
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Installment IV: White Balance
Definition: Determination of the exact color adjustment necessary for a digitalcamera to render a pure white object so that it appears pure white in the
captured image.The assumption is that if white is rendered correctly, all of the other colors will be also. Conversely, if white
has a color cast, it doesnt matter if the other colors are rightthe picture will look wrong.
Lo, the human brain! Among its many wonderful talents, your brain has the ability to restore proper
coloration to most of the physical objects your eyes see. If youve ever shot daylight-balanced 35mm film
under normal tungsten incandescent light you doubtlessly produced images that were brownish-reddish
even though the scene looked normal when you viewed it firsthand. Psychologists have told me the brain
makes corrections to the signals it receives from the eyes because thats way the brain copes with altered
reality. Your brain replaced the blue coloration that was missing from the scene because it needed to keep
things normal-looking.
This ability may be rooted in our evolution from animals that needed to be able to detect subtle color
differences in plants so that they could determine which were edible, ripe or spoiled regardless of the time of
day or lighting conditions. Thats just my guess, but Im sticking with it since most human characteristics are
one way or another related to survival.
Cameras need help to make these adjustments. Yes, many have Auto White Balance settings. But like many of
the other Auto settings, the results are usually pretty close but rarely dead-on accurate. Cameras also offer
Preset and Custom settings. More on those later.
First, lets dispel the misconception that you can easily correct for White Balance miscalculations by using
Photoshop. Experts can salvage some poorly balanced images and many people can make the images look
better, but theres no substitute for getting the white balance set correctly in the first place.
White Balance is not difficult to do or hard to understand. In fact, at the most basic level, all you really need to
consider are three colors: our old friends R, G and B.
The spectrum of visible light ranges from R (red) to B (blue), or more correctly, from near-infrared to near-
ultraviolet. Light color is determined by its wavelength, so it can be objectively measured, filtered and altered.
White is a mixture of all colors (even though that may sound counterintuitive). Pure white objects reflect all
incident light in the 400-700nm (nanometer) range.
Color is objectively identified by its temperature, which is expressed in degrees Kelvin. A color temperature
meter will tell you that noon daylight is around 5,500 degrees and that normal room light generate by a GE
Softwhite tungsten light bulb is closer to 2,900 degrees. On a cloudy day, the color temp might be in the 6,600
to 8,800 range. We call reddish light in the 3,000 degree range warm and bluish light in the higher 7,000
degree area cool even though the numerical value of the cooler temperature is higher. Remember it this way:
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Creative Project
Sunsets and sunrises are dramatically influenced by shifts in white balance.
Remember that when the sun sets, we still see its red, glowing orb even after it
has physically slipped below the horizon. Thats because the long red wavelengths
are diffractingessentially bending over the horizon linelong after the star
itself has disappeared. All of that light is red. A dissimilar thing happens at
sunrise. For creative exercise, set your camera on a tripod, face the sunrise, and
make exposures using every available White Balance option. Work quickly,
because the color temperature of the light will change as you watch. If your
camera allows Custom (Manual Preset) use that setting first to establish a
baseline. Wait until sunset and repeat. This will usually require turning to face the opposite direction.
Try to use the settings in the order that they appear on the menu or dial, or write down the order that you usethem. Lacking that, use the browser software that came with your camera to review the images. It will allow
you to read the Metadata where youll find a record of the White Balance setting associated with each image.
For Nerds Only
If you feel mired down the in the details, theres good reason for it. When were talking color temperature and
white balance, we use the word mired as the contracted form of the expression micro reciprocal degree.
Changes in color temp have a much stronger effect at the lower temperature ranges than they do at the higher.
For example, a 1,000 degree shift from 2,900 has substantially more impact than a similar adjustment at
10,000 degrees. So color scientists devised a system to balance things out. The system is based on this
formula: multiply the inverse of the color temperature by 10 to the exponent 6 (10 6). You get the same result
by dividing 1,000,000 by the color temperature as measured in degrees Kelvin. Special color balancing filters
called decamired filters are used to make adjustments to white balance based on these calculations.
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Installment V: Depth of Field
Definition: The area in front of and behind the point of focus that also appears to besharp.
Youve seen the classic portrait that depicts a smiling face in sharp focus floating over a blurred and obscured
background, as in the photo below. The subject appears to pop right off the page. And youve seen hundreds of
shots of landscapes where the animals in the foreground are as sharp and clear as the mountains behind them.
How can you control exactly whats in focus and whats notparticularly with an autofocus camera?
The phenomenon at work here is called Depth of Field (DOF). Because its
predictable, reproducible and measurable we can use it to our best
advantage. And since its been studied by scientists and optical engineers
for centuries, we know a lot about it.
DOF increases as the diameter of the aperture decreases; in
other words, a smaller f/stop (like f/16) generates greater DOF
than a larger f/stop (like f/2.8). Sometimes people confuse this with sharpness but the two
are quite different. In fact, using a very small aperture can rob you of sharpness. You can learn more about
that by reading the Nerds Onlysection below.
One way to control DOF is by using the right aperture, the aperture that delivers the amount of DOF
that youre after. Shooting in Program or Auto Exposure mode surrenders control over the f/stop, so your
camera must be set on Aperture Priority or Manual if you wish to control DOF. Some lenses have a Depth of
Field scale printed on the barrel. It looks like a symmetrical set of hash marks that delineate the range of focus
when aligned with the aperture thats being used and the distance from the subject.
This is a very reliable way of determining DOF. Unfortunately, it is
accurate without being precise. The increments are simply too inexact. As
you can see in the image above, this particular scale skips from 1 meter to
1.5 meters to 3 meters to infinity. And you wont find a scale on a zoom
lens since the focal length is literally a moving target.
Optical engineers have created DOF charts for many different lenses.
Many high quality lenses include these charts in the owners manual. DOF can be calculated mathematically
using the circle of confusion for a given lens as one of the variables. The term circle of confusion describes a
spot of light that is slightly out of focus when a lens is focused on a given point. You do not need to know
anything about circle of confusion to control DOF.
Some digital SLR cameras have a DOF preview button. Even if your camera does have one, dont trust it 100%.
The DOF that your eye perceives when looking through the viewfinder differs from what the camera sees, even
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when the lens is stopped-down to the shooting aperture. Its a close approximation, but not identical. Use a
DOF chart or the scale described above.
Constants
Wide angle lenses produce more DOF than telephoto lenses (assuming that film format or sensor
size is the same). Some will argue that if you crop a WA image to match the field-of-view of a telephoto lens
the DOF will commensurately diminish. So what? The point remains: put a wide-angle lens on your camera
and youll enjoy more Depth of Field.
Depth of Field always extends 1/3 in front of and 2/3s behind the point of focus. No matter
whether the DOF is deep or shallow, it always follows this formula. This fact becomes more valuable when you
do macro photography.
Depth of Field decreases as the distance between the subject and film
plane decreases. You have VERY little DOF to work with when doing
macro photography and are focused just a couple centimeters away, but
you have extreme DOF when focused at a point near infinity.
All lenses have a Hyperfocal Distance for a given f/stop. If, for example, the Hyperfocal Distance happens to
be 16 feet for a particular lens/aperture combination, everything from one-half that distance (8 feet) to
infinity appears to be in focus. If your lens has a DOF scale as described above, line up the infinity symbol
with the f/stop you are using and you have just set your lens to its Hyperfocal Distance for that f/stop.
Depth of Field sounds like a good thing and usually it isbut not always. If you want to produce dramatic
portraits youll want to limit DOF, as in the image at the top of this story. By limiting DOF you can make a lens
appear sharper. Can you guess why?
Creative Project
Boke (sometimes spelled bokeh) is pronounced bow as in beau plus keh rhyming with the first e in
edible. In Japanese is means fuzzy and in photography its used to describe the parts of a photograph that
are not in focus. Boke can also be used to describe people with fuzzy behavior, but thats another story.
Anyway, some lenses are optimized to produce attractive boke. Your assignment is to explore boke and how it
relates to DOF.
Youll need a lens with a fairly fast aperture: f/3.5 or faster. Position a human subject at least two meters from
a background thats filled with bright colors and small detail (for example, the wall of snazzy-looking cereal
boxes one sees at a grocery store).
Focus on your subject from a distance that allows their shape to occupy about 50% of the frame and shoot
with your lens wide open (largest aperture) in Manual or Aperture Priority. Repeat these steps, but this time
stop the lens down three full stops. Now compare how the out-of-focus backgrounds are rendered.
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Try the same experiment outdoors using a background of flowers or trees, preferably with a bit of backlight
filtering through (so that you can blur a few point sources and highlights).
For Nerds Only
Nearly every aspect of photography involves achieving a balance between competing forces. DOF competes
with sharpness and diffraction is the culprit.
Diffraction occurs when light encounters an obstacle that it cannot penetrate. Light travels in waves that are
parallel when unobstructed. When light waves pass through an aperture they begin to diverge and interfere
with one another. The smaller the opening, the greater the interference. Light waves that are traveling
divergent paths are, by definition, traveling different distances and becoming out-of-phase overall. So at some
point, an aperture that is too small will cause the photo to be unsharp, even though it will have tremendous
Depth of Field. To get the most from your lenses you should know the sweet aperture, the f/stop that
delivers the best image with the fewest aberrations. And you should know at what point diffraction begins to
rob your lens of sharpness.
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how your camera handles exposure bracketing. Some cameras randomly change the f/stop or shutter speed
and you lose control over those critical settings.
The Nikon D5000, for example, adjusts the exposure depending on the exposure mode you select. If you
bracket while shooting in Aperture Priority, it changes the shutter speed. Likewise, in Shutter Priority it varies
the aperture setting. In Program mode it slides up and down the program slope and changes either or both.
And if you have ISO sensitivity set to Auto, the D5000 will automatically adjust that too for optimum
exposure when the limits of the camera exposure system are exceeded (page 103 of the Nikon D5000 Users
Manual).
The second most popular parameter to bracket is White Balance. If youve ever been disappointed by an
otherwise perfect shot thats too green (under fluorescent light) or too blue (outdoors) you can easily
understand why. Its true that in many cases you can correct the color in Photoshop, but its valuable to have a
good clean white to start with and bracketing the White Balance setting is one way to secure that. The better
solution, of course, is to shoot RAW and make your white balance adjustments when you decode the file. But
not every camera records in RAW file format and not every photographer uses RAW every time. That explains
why even high-end RAW capture machines like the Canon EOS 5D Mark II allow you to Autobracket White
Balance.
In reality, the camera is simply adding a finite amount of color bias in one of four directions: amber, blue,
green or magenta. Some cameras offer only amber/blue options. Varying amber and blue allow you to
improve images captured under regular old tungsten house lights as well as daylight. The green and magenta
settings are primarily for certain types of fluorescent tubes. With most cameras that offer Autobracketing of
White Balance, you can set the amount of color bias thats applied. When set on White Balance Autobracket,
the Nikon D5000 captures one image and processes it three ways to alter the color. You can add one, two or
three units of blue and amber plus the normal color rendition.
White Balance Autobracketingalone or in conjunction with manually
applied variationsis a powerful tool and a great, creative way to explore a
scene. And your camera may have another unique feature that can be
bracketed. For example, the Nikon D90 and D5000 cameras allow you to
bracket Active D-Lighting effect. Active D-Lighting is a feature that
essentially extends dynamic range by preserving details in highlight areas and in shadows. Dig out that
Owners Manual and check it out.
One word of caution: make sure the subject doesnt move between shots when youre doing any sort of
bracketing. That seems like common sense, but youd be surprised how many people try to bracket a street
scene, flower thats blowing in the wind or rapidly changing sunset and wonder why the sequence appears
abnormal. If your camera can capture three or four frames per second, the results should be finejust make
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sure you have the drive mode set accordingly. If you are slowly or manually bracketing, be wary of changes in
the scene.
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Creative Project
Bracketing exposureeither automatically or manuallyis too easy to be a Creative Project, but you should
run through the steps enough times that youre comfortable shifting into bracket mode when necessary. And
you might be surprised by the difference a 1/3 or 1/2 stop makes, particularly in scenes that are High Key
(tones ranging from middle gray to white) and Low Key (tones ranging from middle gray to black). Most
important, study the metadata of bracketed images to learn how your camera adjusted itself. As mentioned
above, the ideal way is to keep either the f/stop or shutter speed constant while varying the other.
If your camera offers automatic White Balance bracketing, select a scene
or subject that contains something thats pure white. Purists will want to
experiment with scenes that have two or all three of the primary colors as well. I find that commercial signs,
the sort that hang above business storefronts, often fill the bill perfectly. If you live near an area that has a
carnival-type atmospherea boardwalk on the Jersey shore, for example, or something akin to the equallyflush (although temporary) Taste of Milwaukee celebrationyoull have no trouble finding white signs with
colorful lettering. The assignment is to explore the White Balance Autobracket feature at different times of
day: (ideally) dawn, midday and dusk. Short of that, midday and either dawn or dusk.
For Nerds Only
On May 23, 2001, Minolta Corporation officially introduced the worlds first 5-megapixel digital camera, the
Minolta DiMAGE 7. This model had been exhibitedunder glassat the Photo Marketing Association trade
show the previous February, and in fact won a prestigious DIMA Award from that organization. One of the
unique features of this marvel was Autobracketing of four different parameters.
The DiMAGE 7, fondly remembered by many because of its insatiable
appetite for double-A batteries, featured Autobracketing of Auto
Exposure, Subject Contrast, Color Saturation and Filter Effect. The Filter
Effect option was especially cool. In the right hands, the DiMAGE 7 was a
powerful tool that offered high resolution, outstanding image quality, a
sharp 7X manual zoom, 28mm wide angle coverage and other leading
features. In many ways it was ahead of its time. It also had another unique
featureone that may incite you to buy one secondhand.
The DiMAGE 7 lacks an IR-cutoff filter. That means IR (Infrared Light) passes freely to the CCD. Used with a
deep red IR filter, you can capture some extraordinary IR images. To the right is an image captured with a
DiMAGE 7 by noted photographer and infrared expert Steve Rosenbaum. Well learn more about IR in future
segments of Missing Pages.
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Installment VII: Megapixels
Definition: Citing megapixels (MP) is a popular shorthand way to expressthe resolution of a digital camera in terms of how many millions of
individual pixels (picture elements) are present in the image at time ofcapture.
Note the significance of the phrase ...at time of capture in the definition above. Resolution can be occultly
increased through interpolation, a process that analyzes actual data and makes intelligent guesses to increase
the quantity of information. The number of physical pixels doesnt change. The cameras signal processing
engine fills in the blanks based on complex mathematical algorithms.
After an image is captured you can change the number of pixels that it contains, sometimes without even
realizing it. When we Resample an image we change its pixel dimensions. Upsampling involves adding pixels,
while Downsampling requires discarding pixels. Both procedures degrade image quality, sometime
significantly. People often do this indiscriminately when resizing images to print them. Below is an extreme
example of an image thats been degraded by Upsampling.
Resolution has a horizontal
component and a vertical
component. An image that is 1200
pixels tall by 1800 pixels wide
contains 12001800 or 2,160,000
pixels. Thats about 2-megapixel.
One megapixel is not actually one million, although its close. 1MP = 10241024 = 1,048,576, so we accept
with nearly 5% inaccuracy because, well, it really doesnt matter just as long as everyone counts them and
labels them the same way.
Incidentally, an image that measures 12001800 is said to have an Aspect Ratio of 2:3, which is the same as a
46 inch print.
Many camera specifications show one number for Total Pixels and a lower number for Effective Pixels. The
first, larger number indicates how many pixels can be counted on the entire surface area of the CCD or CMOS
imager, including the edges that are not used. The second number is the only one thats meaningful, as it
indicates how many are actually recording data.
How many megapixels do you need?
How many megapixels do you really need? It all depends on what you
want to do with the image. Unfortunately, digital cameras are lumped into
categories based on the number of megapixels they can capture, and
uninformed consumers make erroneous conclusions about image quality
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based on that single label. Having more pixels does not always mean better images. These images were shot
with a humble 3-megapixel camera.
Having more megapixels can offer some distinct advantages, however.
Higher resolution images produce larger prints without loss of quality.
If you make 1319 inch prints, for example, you need all the resolution
you can get. The second advantage, one thats all too often overlooked,
is that you can crop smaller portions of a high-res image and still retain
high quality.
On the other hand, if you are producing images for a website, or mostly
print 810 or smaller, a nice 6-to-10 megapixel camera will serve you fine. Like many photographers,
however, you may cling to the notion that someday youll want to turn
your images into gigantic poster-sized prints. In that case, shoot large
RAW images now and you wont regret it later that is, unless you runout of hard drive space. Read on.
High resolution comes at a high price. More megapixels mean larger files.
Large files make for longer download times and can really fill up a
memory card fast. Ditto your hard drive and backup externals. Its not
unmanageable, but you should be prepared. Think in terms of terabyte
drives in your RAID configuration and youll be okay.
Do not confuse Resolution with Compression.
The Compression variable is often shown on the cameras menu under the heading Quality. Camera makers
essentially hide the squeeze factor by giving the various compression ratio levels clever aliases like Fine,
Standard or Extra Fine. In truth, the compression ratio varies from as much as 20:1 to as little as 2:1 (plus, of
course, uncompressed). It should be easy to understand that the more you squeeze the more you lose in terms
of data. Some folks turn up the compression while keeping the resolution at the max setting to save file space.
Not good. Its far better to keep the compression as the lowest setting and reduce the number of megapixels.
More megapixels can in fact be a very bad thing if the additional pixels are crowded onto the same size CCD.
In other words, some 6-megapixel image sensors can outperform 10-megapixel image sensors with the same
physical dimensions because the 10MP sensor obviously has less space between the pixels. This space is called
pitch and as it decreases the noise level increases. Increasing the number of pixels means increasing the
pixel density, which in turn almost always means noisier images.
There are notable exceptions, and some camera makers have devised ingenious ways to diminish (if not
entirely neutralize) noise. But there is a downside to aggressive noise reduction, too: less sharpness. Few
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DSLR cameras and darn few compacts achieve an acceptable compromise. Thats another reason why its
important for the creative photographer to understand how the Resolution, Compression and Noise
Reduction settings interrelate on their particular camera.
Its very encouraging that the latest crop of popular compact cameras that are aimed at enthusiasts (Canon
PowerShotS90, Panasonic Lumix DMC-LX3, Fujifilm F70-EXR for example) have put the emphasis on image
quality and noise reduction instead of sheer marketable megapixel power. Camera manufacturers do listen to
their customers who demand high quality images, not inflated numerical specifications.
Creative Assignment
Every digital camera Ive ever seen allows the user to dial down the resolution. The Canon EOS 5D Mk II, for
example, offers setting of 21.0, 11.1 and 5.2 megapixels when shooting JPEG and similar settings for
RAW+JPEG. The Creative Assignment for this installment has three parts.
First, with your camera on a tripod, set the highest resolution and lowest compression ratio that your camera
offers and shoot a colorful but stationary subject. Do this in bright light so that image noise does not become
an issue. Repeat this process for every resolution setting your camera offers, but keep the compression ratio
the same throughout. Since different cameras use different nomenclature for Resolution and Compression
youll have to check the Owners Manual. If youre shooting a Nikon D5000, for instance, youll set Image Size
sequentially at Large (42882848), Medium (32162136) and Small (21441424) to get 12.2, 6.8 and 3.0
megapixel images.
Next, repeat the above, but set the compression ratio to the highest level (i.e., most compression). Again using
the Nikon D5000 as an example, you have the option to set the Image Quality JPEG Fine for 1:4 compression,
JPEG Normal for 1:8 and JPEG Basic for 1:16. For this exercise, use the 1:16 setting.
The third step is done with Photoshop (or Aperture, Lightroom or even the browser that came with your
camera). Open two images that were shot at the same resolution setting but at the extremely different
compression settings. Then, with both images open, zoom 100% (Actual Pixels) and critically examine the
differences. If you fail to see any difference, make an appointment with a qualified ophthalmologist. At the
very least you can expect to see the high resolution/low compression appear much better than the low
resolution/high compression. How much better depends on your camera and, to some extent, the subject. A
shaggy dog looks pretty good no matter what setting you use, but a persons facefull of details and skin
texturewill change dramatically based on how you have these two parameters set.
Bonus Assignment: borrow (or buy secondhand) a digital camera that
has a VGA (640480) resolution option. Many current compact cameras,
including the Canon PowerShot SD1200 IS, offer VGA resolution as an
option. Confirm that the camera is set at the low-res setting and carry it
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with you the next time you go out to photograph. You can use your real camera, too, but be sure to shoot
every interesting subject at VGA. When you download and examine the images you will be amazed how good
they can beprovided you dont try to make them bigger than they should be.
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For Nerds Only
The first breakthrough 5-megapixel camera, based on a Sony CCD, was the Minolta DiMAGE 7, shown at the
PMA Show in February of 2001 and introduced to the media at bi-coastal press conferences on May 23, 2001.
Precisely 90 days later, Sony introduced their own 5-megapixel camera, the Cyber-shot DSC-F707. Ironically,
when Minolta abandoned the digital camera market after being acquired by Konica, it was Sony who
purchased all of the Minolta digital camera patents, technology and intellectual property (and hired quite a
few Minolta engineers, as well).
Got film? Dedicated film scanners in the 4000 dpi range can create 40006000 pixel digital images of
extraordinarily high quality. If youre one of us who began taking pictures long before the digital age, consider
a film scanner to resuscitate your collection of negatives and slides. Dont settle for a multi-function flatbed
scanner that also does film part time. If you want the best quality, buy a film scanner that is optimized for
scanning film.
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Installment VIII: Flash Modes
Definition: Preset combination of exposure settings that determine whether or not a built-in
flash will fire and if it does, how it will synchronize with the cameras shutter mechanism and
other camera parameters.
The little flash thats built into or pops up from your camera is simple, right? When its too dark it fires, and
when its bright it keeps its head down and minds its own business.
Wrong.
The flash itself is a marvelously simple invention. It consists of a flash tube, which is just a bulb thats capable
of becoming very bright for a very brief period of time (as short as 1/50,000th of a second), a battery and a
capacitor to store the energy needed to make the bulb get bright. The term recycle time refers to how long it
takes for the capacitor to form (i.e., accumulate enough energy from the battery so that it can intensely
power the flash again). The flash synch speed is the maximum shutter speed that a camera can set when the
flash is active. This differs widely from camera to camera. Some cameras have a hot shoe, which provides
both a secure attachment point and an electrical contact for synchronization.
An Electronic Flash Unit (as the shoe-mounted version is known in the trade) as well as your cameras built-in
flash is remarkable because in many ways a flash is like a jar full of lighting (the spark, not the beverage).
Correct exposure depends on controlling it, and thats not an easy thing to do. The intensity of the flash is
controlled by adjusting the duration. But its not as easy as is sounds. So camera manufacturers, over the
years, have contrived ways to tame the lighting so that youll get more pleasant results. This collection of
controls is called Flash Modes.
Forced Off
Okay, it may seem logical to presume that when the flash is not on its off but thats a faulty assumption.
The Off or Forced Off (Panasonic calls it Suppressed) Mode means that the flash cannot fire. This is an
important distinction because many (if not most) of todays cameras will turn the flash on automatically when
needed, even if you are not particularly expecting it.
Auto Flash
Ahheres the culprit to blame for the mayhem in the paragraph above. In the Auto
Flash mode the flash remains dormant until the camera decides its time to put a
little light on the subject, at which point it signals the flash to move into position and
commence firing.
Forced On
As the name implies, in this mode the flash will fire whether it wants to or not. I often
tell beginners to think backwards and turn their flash ON outside and OFF indoors.
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That exposes them to the benefits of both Fill-in Flash outdoors and Available Light inside. Forcing the flash
to fire outside, even when theres plenty of light, will brighten colors and wash away shadows, especially those
that make human faces look more like masks. Forced On flash also saves your bacon when shooting a backlit
subject.
Fill-in Flash
Not all (in fact, not many) cameras have this feature as a separate mode; instead its usually incorporated into
the Forced On mode. But its worth mentioning because of the concept behind it. The primary light source is
ambient lightthe flash merely fills in the shadows.
Red-eye Reduction
Aside from zombies, glowing red eyes are never flattering. Light from the flash
reflects directly off the retina at the back of the eyeball, and if the flash source is too
close to the lens axis, the result is a lifeless red blaze. As a countermeasure, cameras
use various techniques to cause the pupil to contract, thus reducing the problem.
Some use a pre-flasha softer flash that fires a millisecond before the real flash.
Some use a bright LED that temporarily blinds your subject. Some cameras have
built-in Red-eye Correction that restores natural color AFTER the image has been
captured. Its not a Flash Mode, but its usually more effective than pre-flash. You can
also remove Red-eye in Photoshop.
Second Curtain (or Rear Curtain) Synch
The shutter is not simply a window that opens and closes. Often its more of a moving slit; that is, the first
curtain opens and is still traveling when the second curtain begins to follow it. Normally, the flash fires as
soon as the shutter opens. When set to Second Curtain (or Rear Curtain) Synch the flash goes off just before
the shutter closes, which affords enough time for ambient light to impact the exposure. Use this mode to
capture mood lighting or to show the natural lights that appear in the background behind your subject.
Flash Bracketing
Flash bracketing is the same as regular exposure bracketing, except that that flash is the illumination source.
This is an underused feature partly because few cameras implement it well except at very close range (despite
what their instruction books claim). For rapid-fire Flash Bracketing the flash must be able to recycle very
quicklyalmost instantaneously. Play with it and use it if you can.
Creative Assignment
Turn your flash OFF indoors and ON outside. Thats rightthe opposite of what youve
thought (or been taught) all these years. Youll see a positive difference in your photos
right away. Some will turn out positively awful, but more will be greatly improved. As
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you practice this exercise you will learn which situations benefit from Flash ON and which from Flash OFF.
Cycle through the various Flash Modes; heres how. Find a suitable subject, indoors in relatively dim light.
Humans work well (zombies are okay too, for the Red-eye portion) as do other mammals. Try your best to
keep the distance the same and, of course, dont change the ISO or zoom. Shoot one or two images using each
of the various Flash Modes. Compare the results and decide which yielded the best image.
Bounce your flashno, no, dont throw it!deflect the light toward the ceiling by taping a business card at a
45-degree angle in front of the flash tube. If youre using an accessory flash that has bounce capability you
probably wont learn anything new from this assignment. Make sure you are shooting where there is a
standard height (8-foot) ceiling so that enough light will be reflected down on your subject. This technique
works great for portraits. Also try rotating the camera 90-degrees and bouncing the flash off of flat, white wall.
(Note that if the ceiling or wall has a strong color it will tint the resultant image.)
For Nerds Only: Strobes and Slaves
Some of the old-timers down at the camera shop may call them strobes but, strictly speaking, theyre not.
Strobes blast a string sequence of psychedelic flashes whereas a Flash emits just one
powerful blast.
Slave Units are self-contained accessory flashes that fire when activated by another
flash. They have a light sensitive sensor that triggers ignition when hit by the sudden
burst of a flash. Since the cameras Flash Synch Speed is typically a slow 1/250 of a
second and the Flash Duration a speedy 1/30,000 or so, there is plenty of time for one flash to fire and set off
a second while the shutter is open. After all, this is happening at the speed of light, and thats as fast as it gets.