purchasing a new lens

7/30/2019 Purchasing a New Lens

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Published onBH inDepth (http://www.bhphotovideo.com/indepth)

Holiday 2012: Purchasing a New Lens

By Allan Weitz

Updated: Tuesday, November 6, 2012 - 9:00am

Im outgrowing the kit lens that came with my camera. Whats a good starting

point for figuring out how to choose my next lens?

There are many variables that go into selecting the best lens for your needs. A good starting point is toestablish what your current lens does notdo. In other words, is my lens not wide enough, long enough or

perhaps fast enough? Does the lens focus close enough, and at the top of many wish lists, is my lens sharp

enough for my needs?

Whats better, zoom lenses or fixed focal

length lenses?

It depends on your definition of the word better. If

you define better as meaning sharper, generallyspeaking, fixed focal length (prime) lenses tend to be

sharper and offer better contrast levels than the average

zoom lenses. But once you start looking at the pricier,

higher-performance zooms, the gap becomes smaller,

and in many cases is a non-issue altogether. As the old

clich goes, You get what you pay for, and this goes

for fixed focal length and zoom lenses alike.

If, on the other hand, your definition of better is

convenient or better yet, more efficient on the

job, thats another case, and zoom lenses are (in most

hands) far quicker to adapt to rapidly changing action,

especially when shooting from a fixed position while

having to respond quickly to fast-moving subjects. In

most cases (and bags), zooms take up less space than

prime lenses. Two or three zooms can cover the focal

range of six to eight or more fixed focal length lenses.

And a camera bag containing two or three zooms is far

easier to carry aboard an airplane than a bag packedtightly with fixed prime lenses.

Some photographers claim that because you have to change lenses more often with fixed aperture lenses,
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theres a better chance of getting dust on your camera sensor. While this argument holds water in theory, the

reality is that many zooms, especially push-pull zooms, create a vacuum effect that sucks dust and moisture

into the lens barrel (and ultimately the camera body) every time you zoom from wide to tele or vice versa.

This is especially true for less expensive zooms that have fewer weatherproofing seals (if any) than their

pricier counterparts, though be advised that dust has been known to find its way into the barrels of the priciest

optics.

Valid arguments for fixed focal length lenses include faster wide apertures for shooting in low light. Even

under bright light, wide-aperture lenses are easier to focus. Wider apertures, i.e. f/2.0, f/1.4, f/1.2, etc., also

enable you to explore the possibilities of selective focusing in which you can isolate your subject from the

foreground and background. With the exception of a pair of f/2.0 zooms for Olympus Four Thirds format

cameras, the fastest zooms only open up to f/2.8, which limits the ability to employ selective focus in your

images. Fixed focal length optics, as a rule, also focus closer than zoom lenses.

Is there a difference between a lens made by the camera manufacturer and

lenses made by third-party lens manufacturers?

Without running side-by-side comparisons between comparable lenses made by original equipment

manufacturers (OEM) and third-party manufacturers, its difficult to answer this question properly and fairly.

Optically speaking, OEM (Nikon, Canon, Sony, Pentax, Panasonic, Olympus, etc.) and third-party lens

manufacturers (Sigma, Tokina, Voigtlander, Tamron, etc.) all produce several tiers of camera lenses ranging

from inexpensive kit lenses to high performance, pro-quality optics. If you were to compare the optical

qualities of comparable lenses from both groups, you may or may not be able to discern much, if any,

difference between them regarding sharpness, tonality, contrast levels and construction.

Are fixed-aperture lenses better than variable-aperture lenses?


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Less expensive zoom lenses usually have slower, variable maximum apertures (e.g. f/3.5 to f/5.6) compared

to faster, and almost always, pricier fixed-aperture lenses. The reason for this variation in the lenses

maximum aperture is that zooms, by nature, are inefficient at transmitting light from the front element to the

imaging sensor (or film plane) as you zoom from wide to telephoto. The physical size of the aperture (or

f/stop) remains the same, but the amount of light that makes it through from one end to the other greatly

diminishes. The net result is that what started out as f/3.5 effectively becomes f/5.6, or perhaps f/6.3,

depending on the lens. To manufacture a wide-aperture lens whose maximum aperture remains constantly

wide throughout the focal range is more complex, hence, pricier.

It should be noted that the effective depth of field of each aperture remains the same, which means that

while the effective aperture goes from f/3.5 to f/5.6, the depth of field remains the same as an f/3.5 lens. You

lose light, but the laws of optics remain unchanged.

The plus side

of variable-aperture lenses is that they are lighter, smaller and less expensive. If you plan on hiking all day

theres much to be said for packing a lighter lens. The downside is, the smaller the aperture, the less

responsive your light meter becomes. It's just as accurate, but it might take a wee bit longer to lock an

exposure, especially in dimmer light. A more serious issue has to do with your autofocus system, which

becomes noticeably slower as the light levels begin to drop off.

This is important because almost all AF systems start to falter at about f/8. What this means is, if you are

using a lens that has an effective maximum aperture of f/5.6 and you add a Polarizing filter to it, which eats upabout two stops of light, your effective maximum aperture is now f/11. Ditto that light loss if you plan on using

a 2x teleconverter. And if youre thinking of using a Polarizing filter and a 2x teleconverter, your widest

aperture will now be an effective f/22. Even if youre using an image-stabilized lens, youre going to be hard

pressed to handhold your camera and manage to capture sharp images.

The more expensive 70 to 200mm lenses have maximum apertures of f/2.8, which is faster, and remain at

f/2.8 throughout the entire zoom range. Add a Polarizer or 2x teleconverter and you are still shooting at an

effective aperture of f/5.6, which under low-light conditions might slow the focusing system down a bit, but

certainly will not jeopardize the sharpness of the captured imagery.
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Another advantage of faster, wider-aperture lenses is their ability to isolate the subject from the foregroundand background of the photograph. Commonly known as selective focus, this is one of the creative benefits

of shooting with faster lenses. By selecting a wide aperture and faster shutter speed, you eliminate

unnecessary foreground and background distractions within the frame, which in turn directs the viewers eyes

to the subject of your photograph, be it a person, place or thing.

Though conventional wisdom says you have to stop your lens down when shooting on bright, sunny days,

higher shutter speeds of up to 1/8000-second enable you to shoot at wider apertures almost anytime and

anywhere.

It's important to note that while variable-aperture lenses tend to be less expensive, many of them are alsoquite sharp. A bit of research can yield inexpensive optics that do not sacrifice image quality.

What are f/stops?

Lens barrel aside, a camera lens is composed of two main components: the clusters of individual glass


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elements and an iris, which is the circular opening created by a set of curved blades that open and close to

allow controlled volumes of light to enter the lens and transmit the image to the cameras sensor. (The pupil in

your eye works the same way, by opening up wider in the dark or smaller in bright light, to allow the

necessary volume of light to enter your eye for a proper exposure.)

The iris opens and closes at specific increments called f-stops, which work in conjunction with the cameras

shutter to allow the correct amount of light in to create a proper exposure.

The f-stop of a lens is determined by dividing the focal length of the lens by the diameter size of the entrance

pupil, i.e., the lens opening. For example, a 100mm with an entrance pupil diameter of 25mm will have a

maximum aperture of f/4.0, because 100mm divided by 25mm is 4. So, on a 100mm lens with an entrance-

pupil diameter of 25mm, when the calibration is written f/4.0, this means "focal length divided by 4."

Just as shutter speeds double (or halve) the time the shutter remains open as you adjust it up and down, each

time you change the f-stop you either double or halve the amount of light entering the lens, and together

shutter speed and f-stop create exposure settings (or the ratio of time/amount of light entering the lens).

To best illustrate how shutter speeds and f-stops work together, think of filling up a glass of water. If you onlyopen the faucet slightly (i.e. a small aperture) it takes longer to fill the glass, as compared to opening the

faucet to full volume (i.e. the widest aperture), which fills the glass in correspondingly less time.

Shutter speeds and apertures operate in a similar fashion. The wider the aperture (f-stop), the shorter the

shutter speed will be, and vice versa. The size of the glass and the amount of water it will holdi.e. the

proper exposureis a fixed quantity. The only variable is how fast or how slowly you want to fill it.

If youre shooting in Program or Auto mode, your

camera does this automatically. As you learn more

about your camera, you can make adjustments to each

of the cameras exposure modes (Program, Aperture

Priority, Shutter Priority and Manual). You can control

the f-stop and shutter settings to achieve different visual

effects. To learn more about the exposure settings of

your camera, you should refer to your cameras

manual.

The A setting on your shutter-mode dial does not

always mean Automatic. Unless your digital camerahas separate settings for both modes, the A frequently stands for Aperture Prioritya mode in which you

set the f-stop and the shutter speed is automatically set to a speed that complements the chosen f-stop.

Shutter Priority is the reverse mode, in which you set the shutter speed and the f-stop is set automatically.


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So, lens speed refers to the maximum apertureor f-stopto which your camera lens can open up, and the

faster the f-stop, the easier it is to shoot under low light and freeze fast-moving subjects.

Another lesser-known benefit of fast lenses, as mentioned above, is that the wider the maximum aperture, the

more responsively your cameras autofocus system will perform, especially in lower lighting. Ditto, the

cameras metering system.

Push-Pull versus Two-Touch zooms: Is there an advantage to one over theother?

Zoom lenses come in two design styles: push-pull and two-touch. Push-pull zooms utilize a single zoom/focus

ring that you push and pull to zoom, and twist to focus. A two-touch

design utilizes two separate rings, one for focus and one for zoom,

with no pushing and pulling. Push-pull designs tend to be found on

less expensive lenses.

While there are more than a few push-pull design zooms on the

market that are optically fine, they can become problematic to use

over time when the guides and threading within the zoom barrel start

to wear down and get wobbly.

The first sign of this problem is when you mount your camera aimed

up or down on a tripod, only to find the law of gravity tugging the

lens barrel downward when you let go. Two-touch zooms do not

suffer from this zoom creep. Another good argument for two-

touch zooms is that you can adjust the focus of the lens without

changing the zoom position, and vice versa, whereas with a push-pull lens you invariably change both the focal length and focus every

time you touch the zoom/focus ring.

And as mentioned earlier, the push-pull action also creates more of

a vacuum effect, which sucks dust and other forms of airborne

particles into the lens barrel as you zoom in and out, unlike two-

touch zooms, which are less prone to dust issues.

Whats Internal Focus and how important is it

when considering a lens?

Internal focus (IF) is an important design feature thats usually (but

not always) found in pricier zoom optics. You can usually tell if a

lens isnt an IF design if it protrudes two to three times its normal

length as you zoom and focus it. If the lens remains the same size as

you zoom in and out, most likely its an internal-focus lens.

If you plan on using a polarizing filter, you should stick to an IF lens

since most non-IF lens barrels rotate as you zoom and/or changefocus, which can prove to be a real nuisance with polarizers.

Another advantage of IF zooms is that when mounted on a tripod

they dont creep like an old push-pull zoom when you aim them up


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or down. And because the lens barrel on IF lenses doesnt zoom in and out (like a push-pull zoom lens), you

are less likely to suck dust into the lens barrel every time you adjust the lens settings.

Image-stabilized lenses cost more than non-image-stabilized lenses. Are they

worth it?

Image stabilization (IS), a.k.a. Vibration Reduction (VR), Shake Reduction (SR) and Optical Image

Stabilization (O.I.S.) is another factor to consider when purchasing your next lens. Image stabilization worksby counteracting any sharpness-robbing effects of camera shake and is quite useful especially if your lens is a

slower, variable-aperture model and you plan on shooting under less- than-favorable lighting conditions.

Some manufacturers offer the same lens with or without IS, depending on your needs or budget. Keep in

mind that an IS-enabled lens can make the difference between a tack-sharp image and a marginally sharp

image, especially if you tend to shoot under low-light conditions.

Pentax DSLRs have internal image stabilization systems (Pentax Shake Reduction {SR} System) built into

them, which enables image stabilization with all Pentax lenses, including older manual-focus lenses. Similarly,

DSLRs from Sony feature their own SteadyShot INSIDE image stabilization systems built into every Alphaseries camera to better ensure sharp imagery regardless of which Sony (or Minolta AF lens) you happen to

be using.

Whats the difference between a macro lens and a lens that features close

focusing?

The precise definition of a macro lens is a lens that focuses down to life size, or 1:1. But it goes further than

that.


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All macro lenses focus close, but not all close-focusing lenses are macros, and the difference lies in the design

of the lens. Most lenses have a curved field of focus, which often complements the curve of the front lens

element. What this means is that when shooting close-ups at the lenss widest aperture, the center of theframe is sharp while the edges become progressively softer as you look toward the corners of the frame.

Macros are designed with flatter fields of focus, which means when focusing straight-on at a flat surface, the

center of the frame and the corners are equally in focus. As a rule, macro lenses are also sharper overall at

closer distances than non-macro lenses. While you can always stop the lens down with standard lenses, they

never quite measure up to the resolving power and contrast levels of a good macro lens.

Macro lenses are available in various focal lengths, and almost all of them can focus down to life size.

Depending on your needs and what you plan on photographing, you should consider your options when

choosing the best focal length for your needs; it is often easier to photograph a subject at a respectabledistance than something up close.

What about lens construction and weatherproofing?

If you pick up any number of lenses, you'll quickly note that some feel solid and hefty and some feel not-so-

solid and hefty. As mentioned earlier, there are more than a few inexpensive lenses that optically speaking,

are quite good but as a rule you get what you pay for. The more expensive lenses tend to have smoother,

more positive action as you zoom or focus them, not to mention little or no wobble in the barrel and lens

mount. If you plan on using your gear on a regular basis, and in less-than-desirable conditions, youre herebyadvised to bite the bullet and buy the better lens.

Weatherproof and dustproof construction are other advantages of pricier glass, and again, if you plan on

going on safaris, to the beach, out on the lake, snowboarding, skiing and other activities or locales beyond

your patio, the integrity of the lens you buy should be a consideration.

Weatherproof does not mean waterproof. Though some manufacturers make impressive claims about water

resistance, be advised that if you go diving or venture out in a hurricane, you run the risk of voiding your

warranty. Weatherproof lenses can weather tropical humidity and the occasional splash or rain shower, but

not full submergence into water.

Will multi-layer lens coatings, aspheric surfaces and exotic glass elements make

a difference in the quality of my photographs?


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Just as construction and weather/dust resistance should be a consideration when purchasing a new lens, the

quality of the glass is equally important. Extra-

low dispersion glass (ED), Fluorite (FL) and

advanced lens coatings are also important

considerations.

When you focus your lens, the image you are

viewing consists of all of the colors of the visiblespectrum. Unfortunately, all of these

colorsred, orange, yellow, green and

bluedo not fall into focus at the same point.

The advantage of ED, FL, other specialty glass

and advanced lens coatings is that together they

help bring all of the colors into focus in a

narrower plane, and when all of the colors fall

into place together, your pictures contain better

color saturation and look sharper overall.

Aspheric lens surfaces are employed in lens design since they help maintain even sharpness toward the edges

of the frame, where many other lenses resolving power tends to fail. The net result of these combined optical

features is better color saturation and contrast, which in turn results in better, sharper-looking images.

What kind of accessories should I consider to go along with my lens?

Two accessories you should consider are a lens shade and a UV filter. Many lenses come with a lens shade,

some dont. Lens shades (or hoods) help block stray light from striking the front surface of the lens, whichcan otherwise cause lens flare that reduces contrast and color saturation.
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UV-reduction filters serve dual purposes, the first of which is to reduce the image-degrading effects of

ultraviolet light, which is prevalent when shooting outdoors in bright sunlight. UV filters also serve as a

protector of the front lens element, which is always subject to dust, smudges and worse. And as any pro can

tell you, its cheaper to replace a damaged or scratched filter than it is to replace the front element of the lens.

Lens Attribute Comparison Chart

Lens Attributes Advantage(s) Disadvantage(s)

Fixed Focal Length LensesFaster (Wider) maximum

apertures & closer focusing

You have to swap lenses to

change focal lengths.

Zoom LensesFlexibility. There's little or noneed to change lenses on the

fly.

Zooms are usually heavier and

slower (aperture-wise).

Push-Pull ZoomsLess expensive to

produce/purchase

Prone to barrel wobble and

barrel drift with heavier use.

Every time you zoom, you need

to check focus.

Two-Touch Zooms

More precise, no need to

check focus each time you

zoom. Less prone to barrel

wobble and focus/zoom drift

when shooting with lens facing

upward or downward

Variable-Aperture Zooms

(Usually) smaller, lighter and

less expensive than fixed-

aperture lenses

Slower maximum apertures

than fixed-aperture lenses and

get progressively slower as you

zoom in tight

Fixed Aperture Zooms Wider/faster maximum aperturethroughout focal range

(Usually) heavier and pricierthan variable-aperture zooms

Less likely to have CPU


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Original Manufacturer's Lenses

(OEM)

communication or

focusing/sharpness issues than

third-party optics

Third-Party Lenses Less expensive than OEMoptics

More likely to have CPU

communication orfocusing/sharpness issues than

OEM optics

Internal Focus (IF)

More precise than non-IF,

optic (usually) remains same

size throughout zoom and focus

range

Image Stabilization (IS)

Enables sharp handheld

shooting at light levels 3-4

stops slower than comparable

non-IS optics

Macro LensesEnable life-size (1:1) imagery

that's sharp, edge to edge

Maximum apertures tend to beslower than comparable focal

length, non-macro lenses.

WeatherproofingProtects your investment

against dust and moisture

Aspheric ElementsHelp maintain higher levels of

edge-to-edge resolving power

Extra-Low Dispersion (ED)

and Fluorite (FL) Glass

Advanced glass manufacturing

technologies that reduce

chromatic aberrations, improve

color and image tonality

Improves color rendition,


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Multicoating saturation and reduces flare

The Takeaway

Fixed focal length lenses are smaller, have faster (wider) maximum apertures, (usually) focus closer,

and are usually (but not always) sharper than zoom lenses.

Zoom lenses are more convenient. Rather than changing lenses, you merely have to turn a ring (or push

and pull).

Two or three zoom lenses take up less space in your bag and are easier and lighter to carry around

(and carry onboard an airplane) than six to eight fixed focal length prime lenses.

Lenses made by your camera manufacturer are sharper, better made and pricier than third-party lens

manufacturers except when they arent.

Variable-aperture lenses tend to be lighter, smaller and less expensive than comparable fixed-aperture

lenses.

If you plan to use teleconverters and Polarizing filters, you should consider sticking to wider-aperture(faster) lenses.

Two-touch zooms are preferable to push-pull zooms.

Image stabilization is a good idea because theres nothing worse than a photograph that would be

terrific if it werent so blurry.

If you plan on shooting lots of close-up pictures, consider a true macro as opposed to a lens that

features close focusing.

Weatherproof does not mean waterproof.

Multilayer coatings, ED glass, fluorite glass and aspheric surfaces are good things.

As a rule, you get what you pay for.

Tuesday, November 6, 2012 - 9:00am

Show Updated:

Comments

Submitted by Mike on Monday, December 3, 2012 - 10:13am.

I really like the article on lenses. There were several key factors that were left out on stabilized lenses. One is

the time for a image or picture stabilization to work, can you imagine how long it takes to spin that large ring

in your favorite Canon lens. I have missed some shots waiting for the stabilizer to work. Another key factor,

is battery life of those big stabilized lenses, most forget to mention that you will need to carry several camera

batteries with you for your favorite lens. Thanks

Submitted by Andre on Tuesday, November 20, 2012 - 10:00pm.

Many thx

!Very helpful

Submitted by Roger Dreyling on Sunday, November 18, 2012 - 9:53pm.


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A very helpful and informative summary. Clearly and understandably written. I am making a copy for future

reference when purchasing my next lense. I also looked at my four existing lenses to review their features.

Suggestion for another topic: Compare the features of cameras with a "full-frame sensor" to cameras, such as

Canon's 7D, that do not have a full-frame sensor.

Submitted by W B Lim, Singapore on Tuesday, November 13, 2012 - 3:57am.

Great article! Very informative.

Submitted by Susan on Monday, November 12, 2012 - 9:38pm.

i'm looking at buying a travel lens. i wouldnt normally want to drop down in quality, but i'm doing a 'people'

piece in Calcutta over the Xmas break, and want a 'snap it quick' lens that will suit any situation. i have been

looking at some 18-135mm, 28-135mm, 18-200mm (Canon lenses and third party lenses) (for a Canon

body btw - 7D), but can't decide because i'm worried about losing sharpness in my images. Anyone have any

thoughts, advice, tried these lenses, are they sharp at all? Is it possible to get a sharp kit lens? Ive never used

one.

Cheers!

Submitted by Dennis on Thursday, November 15, 2012 - 2:40pm.

At this time, there is no lens that can do it all, i.e.one that is sharp, fast, small, big zoom, wide stop. It is

impossible. You need to choose what features are more important and affordable. The 4 8 oz super

sharp f/2.0 18-200mm that retails for $59.95 has not been made yet!

All lenses of comparable design will be about the same quality and price. Of course as my Dad used to

say You will get what you pay for. If you pay the least, you will get good but not great image/build

quality. That being said many people appear perfectly happy with their everything lenses.If this was my situation and I could only take one lens I would be thinking for the 7D of either the 17-

55mm f/2.8 or the 24-105 f/4. No compromise in image quality; in fact about as good as it gets. If not

quite the range of 18-200, you can work around that by having zoom feet!

Submitted by Susan on Saturday, November 17, 2012 - 6:08pm.

yes, naturally it's tough having to choose just one. ive never had this situation before. i dont want to

have to change lenses and i want to cover as much focal length as poss without a major decline in

image quality. i thought seriously of the 24-105mm, i already own the 17-55mm and 17-40mm and

70-200mm, so didnt really want the 24-105mm as it doesnt give me enough 'sneaky' capability for

this trip and F/4, well... So i decided on the 18-135mm stm. it seemed the best all-round for the

money and as it's not tooooo expensive i can 'throw it around' without too much concern ;) thanks

for your insights.

Submitted by Manzell L from B&H Photo on Wednesday, November 14, 2012 - 7:06pm.

If you are looking for a longer-than-normal zoom lens to use as a standard lens, the four lenses I would

recommend (listed in order) would be the Canon EF-S 18-135mm f/3.5-5.6 STM IS lens, the Sigma

AF 18-125mm f/3.8-5.6 DC HSM OS lens for Canon, or the Tamron 18-200mm f/3.5-6.3 XR Di-II LD Aspherical (IF) Macro Lens for Canon. The lenses are listed in order of sharpness. While

they may not be as sharp as a fixed lens or a standard zoom lens with a shorter range, they are both

sharp enough and convenient for travel photography. You should be able to type the name of the lenses

into a website like Flickr and view examples taken by normal users who own the lens to get a feel of the
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images each can create. For your needs, depending on the amount of zoom you need, those would be my

recommendations.


thanks for your advice, i agree with you after much research that for covering all my bases the 18-

135mm stm fit the mark best. So i ordered it from my fave photo shop B&H ;) Got my Indian visa

yesterday!!!! all systems go.

Submitted by JLV on Tuesday, November 13, 2012 - 10:38pm.

I have used the following lenses for most travel and quite happy with the range, also with my 7D, I rarely

us anything other than these 3:

10-22

28-135

70-300

Good luck!


thanks for your reply. i too like/prefer to use my better lenses, but this time i can only go with one.

Submitted by Luis Curran on Monday, November 12, 2012 - 6:46pm.

Can you give me an example of a Canon 'two-touch' lens? Thanks.

Submitted by Dana G from B&H Photo on Wednesday, November 14, 2012 - 4:00pm.

Here is an example of a Canon "two-touch" lens:

Canon EF 70-200mm f/4L USM Lens

Submitted by BigIntoSmall on Wednesday, November 14, 2012 - 10:22am.

The Canon 70-200 L.

Submitted by Paperboard Engineer, Atlanta, GA on Monday, November 12, 2012 - 11:14am.

Great article as usual! I thoroughly enjoy the technical articles by the B & H Technical Experts. They are so

well done and generally are some of the best written in the industry!

Submitted by Art Krueger on Monday, November 12, 2012 - 10:43am.

Great article and guide.

Can you pls explain what is a "Prime Lens" and how that designation is disclosed to the customer.

Submitted by Mark S from B&H Photo on Monday, November 12, 2012 - 5:59pm.

Hello Art -

It's a lens that does not zoom. A prime lens has a fixed focal length which means it has only one focal


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length. A prime lens may be designed for a specific use like Fish-eye, Perspective control for architectural

shooting, Macro for extreme close-ups of tiny subjects, etc.

Prime lenses are generally lighter and smaller; more compact than their zoom lens counterparts. They

are generally "faster", as well, offering wider apertures allowing more light to enter the shutter plane,

which in turn, allows faster shutter speeds for hand-held, low-light shooting.

Submitted by thesouthdakotacowgirl on Monday, November 12, 2012 - 11:29am.

A prime lens has no zoom function. The zoom is your feet, if you will. They are usually faster, and open to

a very wide aperture -f/1.2 or f/1.8.

Submitted by Don on Monday, November 12, 2012 - 11:18am.

Really good article! I read the part about two touch vrs one touch lens with interest. I have a Sigma 170-

500 zoom that is what I believe you call a two touch zoom. The front of the lens does not creep unless it's

almost straight down. Then it doesn't creep, it falls! But no creep down to maybe 160* or a bit more.Pretty heavy and I guessed that that was the reason it does it. Does take good photo's when I do my

part. One more thing. I'm old and the eyes aren't the best any more so I never manual focus. Could that

be a problem? My photo's look pretty sharp to me.

Thanks!

Submitted by Bill on Monday, November 12, 2012 - 9:49am.

Great lens artical! Thanks.

Submitted by Steve on Wednesday, November 7, 2012 - 4:10pm.

Question on the Nikon AF-S Nikkor 17-35mm f/2.8 ED -

This lens has never-ever been sharp. Tests done across the zoom range and at f/4, f/8, or f/16... even tried

two other lenses (one from a rental house) and still cannot get sharp results.

I'm not being real picky here.. but having no luck or confidence as I use this lens the image is going to be sell-

able.

My question is simple:

I need a replacement lens for this range... any recommendations?

Submitted by hwaldner on Friday, November 9, 2012 - 11:18am.

If you are shooting a DX body. http://bhpho.to/JxbC2N

For Full Frame or FX ( will also work on DX bodies ). http://bhpho.to/efzyj9

Submitted by vik on Wednesday, August 15, 2012 - 5:07pm.

Crisp

Submitted by Richard on Monday, January 2, 2012 - 11:58am.

Well written and very informative, although I knew over 50% of the article I really enjoyed the article. Each

time I take the time to read a B & H article I learn something that helps me to capture moments or objects I
http://bhpho.to/efzyj9


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wan to share with folks.

Submitted by barth36 on Friday, December 30, 2011 - 8:33am.

Great article! Everything you need to know to select a great lens.

Submitted by Ken on Tuesday, December 27, 2011 - 8:53pm.

Generally a great article, but Im not so confident about your discussion of fixed and variable apertures inzoom lenses. The statement that worries me is:

The reason for this variation in the lenses maximum aperture is that zooms, by nature, are inefficient at

transmitting light from the front element to the imaging sensor (or film plane) as you zoom from wide to

telephoto. The physical size of the aperture (or f/stop) remains the same, but the amount of light that makes it

through from one end to the other greatly diminishes.

I have always put the change in f-stop down to the fact that as you double the focal length with a fixed

diameter of lens, the f-stop also doubles (according to the formula f-stop = focal length over diameter). Ive

always assumed that fixed aperture zoom lenses were made so that the aperture was set at the long end but

that the design of the optics is such that image degradation at the shorter lengths with the same diameter of

glass is too great to be used.

I can imagine that amount of light due to changed optics could vary a bit, but not greatly as you suggest.

(This could introduce a discussion of t-stops, but that is scarcely relevant for us.)

(Im sure some people might find a discussion of the numbering of f-stops interesting as well; how they relate

to the square root of 2. Wikipedia has a good article on this at http://en.wikipedia.org/wiki/F-number .)

Submitted by Gordon Christie on Thursday, July 19, 2012 - 9:28pm.

Lens have always had grouping on how light is makes it to the film plane. I have use fixed focal length lens

over the years with very good results. With all the zoom lens fast or slow it is a tough call depending on

what your subject mater is mainly, & if you do shooting in the 2.8 as a rule? Lens performance has been

a ongoing subject for every new optic that come's out nikon, canon, after market. Unless you are going

very large on the print side this maybe where edge sharpness would be noticed. If there is a focal length

zoom or fixed you are looking to own, rent the lens test it to see if meets your needs before you make

that commitment $$$. Good luck & happy shooting! Ciao G.C.

Submitted by Junior Burton on Tuesday, December 27, 2011 - 5:47pm.

Dec. 27, 2011

Hi,

I just took a scan of the information you e-mailed, it is very informative - great info - I will

give it a thorough reading later - Thanks

jr

Submitted by Dr. Buick on Wednesday, December 28, 2011 - 10:04am.


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I just bought the Nikon 28-300mm f3.5-5.6 VR, and sold my 18-105 mm f3.5-5.6 VR kit lens and 70-

300mm f4.5-5.6 G VR. It was a even investment and I'm happy with the simplified shooting and

sharpness increase.

Submitted by Allan Weitz from B&H Photo on Wednesday, December 28, 2011 - 9:11am.

Thank you , Junior!

Submitted by Antonio Mario on Tuesday, December 27, 2011 - 5:30pm.

Hi Allan,

Thank you for a very informative review.

I must say though that I'm a little bit lost with your comment regarding the Depth of Field. I also read your

article under your link above (in your 1st response) but I continue to fail to see your point.

DOF depends on camera-subject distance, lens aperture and lens focal length. For a given distance, if you set

your zoom (say) to a certain focal length, the DOF will depend on the aperture; the larger the aperture (i.e.,

smaller f/#) you'll get a smaller DOF.

So, if I set a 70-200mm f/2.8 to 70mm, say, as I close down the lens from f/2.8 to f/11, the DOF WILL

increase (for an object at a given distance). This is due to the rays that form the image being closer, on

average, to the lens optical axis (the so-called paraxial approximation) when the diaphragm is smaller.

So, I'm certainly missing something from your point or argument.

In any case, thanks for your article!

Submitted by Allan Weitz from B&H Photo on Wednesday, December 28, 2011 - 9:09am.

OK Antonio, let's give it another shot. Your 18-55mm variable-aperture zoom lens has a maximum

aperture opening of f/3.5 at it's widest angle position (18mm) that "slows down" to f/5.6 at its longest

focal length position (55mm). Now stay with me Antonio, here's the key to the puzzle; the physical size of

maximum aperture of the lens - f/3.5 - remains the same regardless of what focal length you have the lens

set at. What changes is the degree of efficiency with which the lens transmits the light through the lens as

the various groups of lens elements shift back and forth inside as you zoom in and out. And as you zoom

in with a variable-aperture lens, the amount of light that makes it through diminishes, turning your f/3.5lens effectively into the equivalent of an f/5.6 lens. How does that work for you?

Submitted by antonio Mario on Wednesday, December 28, 2011 - 3:28pm.

Hi Allan, thanks for commenting back. I now understand your point of view better. I was

considering, at a fixed focal length, changing the lens aperture; you're considering a fixed physical

aperture, and a changing focal length.

However, I still feel that, even in the situation you describe, the DOF will in general change (if you

don't want to be bored just go straight to my one-before-last paragraph to see my take; otherwise,hang on ;-) ). This is because, even though the physical aperture stays the same as you zoom in, say,

the effective focal length (fl) will change. The change in f/# won't be linear with the fl change because,

as you mention, the lens elements will adjust their relative spacing internally and the entrance pupil,

where the diaphragm sits, will in general move inside the lens. In any case, I feel that, with the change


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in fl, even though with the same physical aperture, the DOF will in general change.

(I did a coarse visual test with my BH-purchased Canon 40D and my Sigma 18-200 f/3.5-6.3 lens in

my living room. With the lens at 18mm & f/3.5, I focused on the windon pane, some 3m/10ft away,

paying attention to how sharp the background looked. It was easily recognizeable, since, with the

lens set this wide most of the things from the plane of focus towards infinity will be very close to

focus. When I zoom to 200mm f/6.3, focusing on the same spot 3m away, the background is clearly

way out of focus. I have to add that, if the 18mm setup is to provide an image of the object beingfocused of equal size as the 200mm setup, then the camera will have to be very close to the object

and the DOF in both such situations will be the same.)

The overall situation might be akin to that of using a tele-extender, isn't it (I know you're familiar w/

all this but please bear with me for a moment). Say you have your fixed fl or zoom lens set at 400mm

f/5.6. If you include a 1.4x tele-extender, it will multiply your initial fl by 1.4x, of course (your lens

diaphragm is still the same inside the lens). The illumination on the detector goes with the inverse of

the f/# squared (or, which is the same, with the inverse of the fl squared at a fixed aperture), so we

loose a factor of (1.4)2 = 2, or 1 stop. We then get 400mm at f/8.

The DOF depends linearly on the aperture (aperture = 5.6, 8, etc) and inversely on the fl squared.

With the tele-extender, it will be then a factor of 4 smaller (than w/o it) because of the fl change but it

will be a factor of 2 larger because it goes linearly with the aperture. The overall change will hence be

that the DOF will be a factor of 2 smaller (than w/o the tele-extender).

From the latter paragraph, in the situation you describe of zooming in and at the same time changing

the aperture, the DOF will NOT change IF the fl changes by a factor equal to the square root of the

aperture change. In your example of a change from 3.5 to 5.6, the aperture change is a factor of

5.6/3.5=1.6. The sqrt of that is about 1.26 or so. So, if you increase the fl by this factor, say from18mm to 18*1.26~23mm, then the DOF will be the same, as you say. But if the fl change is larger

than this factor, such as going from 18mm to 55mm say, then I feel the DOF will be smaller; if the

change in fl is smaller than that factor, the DOF will be larger than initially at the new fl setup.

Sorry for being so lengthy. Thanks for bringing up such an interesting topic.

Submitted by davidspyle on Monday, November 12, 2012 - 10:21am.

Thank you!

A great article, only wish it were available as a Pdf. file which I could save.

Thanks again.

dsp

Submitted by Allan Weitz from B&H Photo on Wednesday, December 28, 2011 - 3:53pm.

Antonio, The flaw in your test is that you are comparing the DOF at different focal lengths, and

since DOF APPEARS differently at different focal lengths (though actually ISN'T, but this is

another story) it's extremely difficult to make judgement calls on matters like these.

If you want to run a true test of my explanation you should compare the DOF of two images; one

taken with a fixed-aperture 70-200mm lens (as an example) set to f/5.6 and a variable aperture

70-200mm zoom lens set to f/5.6. Even though the meter will indicate the light value is closer to

f/8 or less, the images will appear identical to one another in terms of DOF.


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Submitted by MobyMud on Wednesday, December 28, 2011 - 1:18pm.

Alan,

Wow, that was the kicker. I'm not optics expert, but I've been shooting with a variable zoom lens

since around 1978 and I've always assumed (like some others here) that the effective f-stop

decreases because, as the elements move around, some of the actual aperature is reduced. now I see

the folly in that thinking: if the actual aperture was decreased, the decrease would not be in the focalplane and .'. would be out of focus and creating a vignette effect and not a uniform about of light

across the frame. The way you explained it, I can see the light is getting stretched out like salt

water taffey and thus the EV will decrease.

Light dawns over marble head. Thanks again!

Gene

Submitted by Allan Weitz from B&H Photo on Wednesday, December 28, 2011 - 3:27pm.

Now you have me stumped Moby. After reading you feedback I went back to test my theory

adding your hypothisis into the equation and now I have saltwater taffey gumming up my aperture

blades!!!

(Don't worry.... I didn't gum up my lens, and I'm glad I cleared up your 34 year-old lens

question...)

Submitted by MobyMud on Thursday, December 29, 2011 - 10:17am.

(I typically use taffy to remove the dust from my aperture leafs, with care it won't stick, justbe careful pressure pumping it through the seams).

As to the DOF question, I'm sure your right, but why doesn't zooming in decrease the

ACTUAL DOF? I always thought that a sufficently wide angle lens at f/8 focused everything

clearly enough. I seem to remember at Nikon house (remember Nikon House?) that the

6mm super wide angle didn't even have the ability to focus.

And, while I have you on the line, what are you thought re: a good kit for my brand new

D7000 which Santa carefully slid down the chimney with? It came with the 18-105 VR, I've

heard that the 18-200 VRII is "better" as an overall carry along and worth the $500 upgradeit will cost me as I won't have to swap lenses.

I'm coming from the Olympus world, and was quite spoiled by my 12-60mm f/2.8-3.5 and

my 50-200mm f/2.8-3.5 as well. So, I'm not opposed to changing lenses, but I'm sorry to

lose such a great piece of glass. I also considered the 24-120 F/4, though pricy and limited.

I'd prefer a one lens solution, but I'm willing to go for a two lens solution if the sharpness

increase is significant. From the reviews, I can't see whether that is the case or not, so, why

not ask the expert?

Moby

p.s. Still waiting for the super lightweight super sharp 12mm to 300mm f/2.0 compact zoom.


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Submitted by Scott S on Tuesday, December 27, 2011 - 2:43pm.

Regarding "push-pull" zooms... the ones we called "one-touch" when they were first introduced back in the

'70s.:

Are there even any of those produced for current cameras? The only ones that I can remember seeing in the

last 10+ years are units designed and produced for legacy manual-focus film cameras. Like my old SrT-202.

I've never seen one that was compatible with any autofocus system.

It's not really a critical point except that it seems like a fair amount of effort was used in explaining a non-issue

in an an otherwise very good article.

Submitted by Allan Weitz from B&H Photo on Tuesday, December 27, 2011 - 3:46pm.

Hi Scott,

While you are correct in saying one-touch/push-pull zooms are a breed of another era, they are still

around, Canon's EF 100-400mm f/4.5-5.6 USM L IS being one of them.

And thanks for the feedback.

Submitted by Anonymous on Tuesday, December 27, 2011 - 2:26pm.

not sure if I would ever buy third party lenses. I only buy nikon brand lens intended for USA market. I also

prefer fast lens over variable zoom lens. But I do believe that two must have lenses are 50mm 1.4f and 28-

300mm zoom.

Submitted by James C. Megas on Tuesday, December 27, 2011 - 1:58pm.

I find articles like this extremely useful. I would like to see them throughout the B&H Photo site. For

example, an article on choosing a light meter. I particularly like the fact that these articles *explain* the

equipment in detail, rather than merely try to sell. Knowledge is power. Thank you.


These guides are extremely well composed and very helpful. Thanks for including them.

Submitted by Chuck Irwin on Monday, November 21, 2011 - 3:42pm.

Thanks for the terrific information on Lens. This is a keeper! Look forward to future articles. Regards, Chuck

Submitted by Michael on Monday, November 21, 2011 - 11:56am.

To be fair, there are also disadvantages to using UV filters.

Most digtal cameras are not sensitive to UV light, so there is no need to filter it out.

Although a filter can keep a fingerprint off your lens, a fingerprint on the filter is just as bad. Most lenes havebetter coatings than your average filter, so you are better off cleaning the lens than a filter.

Digital sensors are shiny, puting a filter on your camera greatly increases the chance that light will bounce

back and forthe between the filter and the sensor which reduces image contrast.


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Most importantly, contrary to popular belief, a good filter can cost more than replacing the front element of

your lens.

On the plus side, UV filters are a high-profit item, and by buying them we make it possibel for the store to

keep lower prices on other items.


"Most digtal cameras are not sensitive to UV light, so there is no need to filter it out."

Any rule of thumb for how a hobbyist might determine which digital cameras are sensetive to UV?

Great article, very informative.....thanks!!

Submitted by Chuck C from B&H Photo on Wednesday, December 28, 2011 - 11:47am.

Hello,

Digital cameras are not sensitive to UV light because their sesnors have UV cut filters covering them.Digital camera sensors are sensitive to UV and IR and a common practice is to remove this filter for

special affects imaging. We ofcourse do not recommend removing this filter.

Submitted by Anonymous on Wednesday, December 28, 2011 - 10:37pm.

So people actually open their cameras and remove the UV cut filter? Wow, that effect better be

really cool.....even if it is, I'd never do this......but then, I'm just a hobbyist.

Thanks for the explanations guys!

Submitted by Michael on Wednesday, December 28, 2011 - 9:46am.

The rule of thumb is that digital cameras are not sensitive to UV light.

Submitted by BWBPhoto on Wednesday, November 23, 2011 - 10:36am.

I have *never* used a UV filter in the last 20 yrs. I believe it is far more important to have a lens hood

on the lens at all times. this protects the front element better than a filter can and is far more beneficial for

making sure you get the best images out of your lens

Submitted by Susan on Monday, November 12, 2012 - 9:40pm.

Yes I would agree with that. A hood offers more protection and doesnt lower image quality like

another layer of glass - no matter how well cut - does.

Submitted by Andy on Monday, August 8, 2011 - 11:47am.

From the article: "It should be noted that the effective depth of field of each aperture remains the same,

which means that while the effective aperture goes from f/3.5 to f/5.6, the depth of field remains the same as

an f/3.5 lens. You lose light, but the laws of optics remain unchanged."

Are you certain of this? if you take a photo with a 70-300 f/3.5-5.6, and are at the extreme telephoto end of

the zoom, wouldn't that photo have a dof consistent with a 300mm f/5.6 lens and not a 300mm f/3,5 lens?


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Submitted by Allan Weitz from B&H Photo on Thursday, August 11, 2011 - 2:44pm.

Hi Andy,

Your question is a good one, and one that pops up on a fairly regular basis.In response to your comment

- and similar comments from others, I went ahead and wrote a quick 'Tips & Solutions' response, which

can be found by following the following link;

http://www.bhphotovideo.com/indepth/photography/tips-solutions/variable-apertures-and-depth-field

And thanks again for taking the time to write us!

Submitted by James on Tuesday, June 21, 2011 - 12:47am.

Really helpful article. Very well written! Thanks for your time and knowledge! :)

Submitted by Anonymous on Tuesday, June 14, 2011 - 4:05pm.

Wow! This article really answers the beginner photographers basic questions.

Submitted by Bobber on Tuesday, June 7, 2011 - 5:15pm.

Thank you for doing this. When trying to get into photography, there are so many little details that old pro's

take for general knowledge when trying to help a beginning level enthusiast like me. These comparatives that

explain pros and cons of choosing different option in lenses really helped me a lot. This was extremely

informative to me.

Submitted by Anonymous on Sunday, June 5, 2011 - 11:53am.

very well put together article. look forward to more. Thanks IL

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