APERTURE.Inoptics, anapertureis a hole or an opening through whichlighttravels. More specifically, the aperture of anoptical systemis the opening that determines the cone angle of a bundle ofraysthat come to afocusin theimage plane. The aperture determines how collimatedthe admitted rays are, which is of great importance for the appearance at the image plane.[2]If an aperture is narrow, then highly collimated rays are admitted, resulting in a sharp focus at the image plane. If an aperture is wide, then uncollimated rays are admitted, resulting in a sharp focus only for rays with a certain focal length. This means that a wide aperture results in an image that is sharp around what the lens is focusing on and blurred otherwise. The aperture also determines how many of the incoming rays are actually admitted ('allowed into') and thus how much light reaches the image plane (the narrower the aperture, the darker the image for a given exposure time). In the human eye, thepupilis the aperture.An optical system typically has many openings, or structures that limit the ray bundles (ray bundles are also known aspencilsof light). These structures may be the edge of alensormirror, or a ring or other fixture that holds an optical element in place, or may be a special element such as adiaphragmplaced in the optical path to limit the light admitted by the system. In general, these structures are called stops, and theaperture stopis the stop that determines the ray cone angle, or equivalently the brightness, at an image point.In some contexts, especially inphotographyandastronomy,aperturerefers to thediameterof the aperture stop rather than the physical stop or the opening itself. For example, in atelescopethe aperture stop is typicallythe edges of theobjective lensor mirror (or of the mount that holds it). One then speaks of a telescope as having, for example, a 100 centimeteraperture. Note that the aperture stop is not necessarily the smallest stop in the system. Magnification and demagnification by lenses and other elements can cause a relatively large stop to be the aperture stop for the system.Sometimes stops and diaphragms are called apertures, even when they are not the aperture stop of the system.The word aperture is also used in other contexts to indicate a system which blocks off light outside a certain region. In astronomy for example, aphotometricaperture around astarusually corresponds to a circular window around the image of a star within which the light intensity is assumed.[3]

What is an "aperture" ?

Apertureis referred to the lens diaphragm opening inside a photographic lens. The size of the diaphragm opening in a camera lens REGULATES amount of light passes through onto the film inside the camera the moment when the shutter curtain in camera opens during an exposure process. The size of an aperture in a lens can either be a fixed or the most popular form in an adjustable type (like an SLR camera). Aperture size is usually calibrated inf-numbersorf-stops. i.e. those little numbers engraved on the lens barrel like f22 (f/22),16 (f/16), f/11, f/8.0, f/5.6, f/4.0, f/2.8, f/2.0, f/1.8 etc. Each of this value represents one time the amount of light either more or less in quantity. Meaning to say, f/16 will let in1Xthe amount of light than a diaphragm opening of f/22 and so forth; while on the other hand, an aperture of f/4.0 will let in 1X lesser than that of f/2.8 etc.Note: the diaphragm blades inside this manual focus Canon FD lens control the amount of light passing through the lens that eventually hitting to the film during an exposure process. The 'amount', or simply explained in layman term -openingchanges according to selection of aperture (f/number). In this case, it is indicated by the f-numbers that imprinted on the lens barrel.LENS SIDE:- If a simple word "diaphram" can be confusing to you, just try to think numbers engraved on the lens barrel areNOTreferred to aperture diaphragm BUT rather, there are just number to let you refer the size of the lens diaphragm. So, if you are new to this, just memorize these numeric settings that will do, as they represent the corresponding size of the lens diaphram inside the lens and let you determine and control how much light you would require to let into the camera for a proper exposure by way of selecting an appropriate aperture diaphragm from large to small (lens opening).But technically, these numbers refer to the relative physical opening of the lens diaphragm. So, don't worry about the confusing part of them.Modern Autofocus SLR cameras may have a different ways in manipulating the aperture. One of the trend is - the aperture value is now control via a thumb wheel on the camera (usually near the shutter release button) and the AF lens has no aperture ring to alter the value. Each camera manufacturer usually has their own series of lenses under a trade name to verify its usage, various compatibility issues with their previous camera model's function etc. For an instance, Canonmanual focuslenses are called "FD" or "FL"; while their newer series of autofocus lenses (AF) designed for theirCanon EOS Seriescameras are referred as "EF" (Electro Focus). Each of these MF/AF lenses has their own respective way to illustrate the control of aperture in the camera. When you turn the aperture ring on a lens to vary the aperture, you will be able to check visually the set opening of the lens diaphragm (Opens bigger or stopping smaller). *here in this section, I am confining thediscussion within the MANUAL FOCUS lenses ONLYbecause the proportion of used equipment forms the basis for a cheap, easy entry for potential new serious photographers.

What is shutter speed ?The aperture diaphragm of a lens (bigger or smaller values) AND timing (open and close) of the camera's shutter curtain -BOTHperform the tasks of regulating the amount of light entering the camera and expose onto the film. The shutter speed scales engraved on the shutter speed dial of conventional camera bodies with a shutter speed ring OR via some flickering digital numerals on the LCD screen like: 1/8000, 1/4000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 or -1, -2 etc. are essentially indicators of the duration (timing) at which the shutter curtain opens up and closes during an exposure process. A 1/125 setting means the shutter curtain open and close within one hundred and twenty five of a second while 1 means an one full-second the shutter opens up during exposure to absorb the available light source onto the film to form anexposure.Different selection of shutter speeds will yield different kind of visual effect on a final photograph.Generally,a fast shutter speed can freeze action while slow speed can blur your image.I am not indicating these are fixed rules. If you understand the nature of how various shutter speed(s) will affect an exposure, you may put them to creative use to enhance the effect - like other than freezing a fast action scene, a slow shutter speed can also put to good use in portraying movement. You can try on to "PAN" a moving subject by following its direction or simply generates a sense flow of movement.But MOST people relates SLOW means BLURRING AN IMAGEwhich leave little for them to select this alternative to try them out. Well, it is excusable because in mostPR-type of photography (photo session on public relation matters like wedding, gathering, seminars, or personal domestic duties for some privileged group - includes your wife, mistress or girl friends..), who would appreciate a defocus or blurry images ?BUT- for the creative minded photographer,slower shutter speed sometimes may create a more powerful visual impact than images taken with action-freeze high shutter speed(s), say, a free flowing river, traffic, a flock of birds taking off or even speed-demons on a race track.. etc..A camera operating in manual mode or a mechanical camera requires you to set the shutter speed and aperture value on the lens manually. In an automatic camera, there is usually at least one type of automatic exposure mode is available. Because of complication of mechanism involves, most camera manufacturers offer onlyAperture Priority AEorProgrammed AEmodes on theirEARLYelectronic camera models. A good example isMinoltaandCanonwith their MD andFDmountcameras and lenses while in some exceptional case, such automation was made possible using a mechanical device such as Nikon's F2 with their EE Aperture Control Unit.

However, by early '80 with development and refinement made on both cameras and lenses (Most would require a new series of optics), majority of them started to offer "Shutter Priority AE" and "Intelligent Programmed AE" as well.

1) What is ISO?In very basic terms, ISO is the level of sensitivity of your camera to available light. The lower the ISO number, the less sensitive it is to the light, while a higher ISO number increases the sensitivity of your camera. The component within your camera that can change sensitivity is called image sensor or simply sensor. It is the most important (and most expensive) part of a camera and it is responsible for gathering light and transforming it into an image. With increased sensitivity, your camera sensor can capture images in low-light environments without having to use a flash. But higher sensitivity comes at an expense it adds grain or noise to the pictures.Every camera has something called Base ISO, which is typically the lowest ISO number of the sensor that can produce the highest image quality, without adding noise to the picture. On most of the new Nikon cameras such as Nikon D5100, the base ISO is typically 200, while most Canon digital cameras have the base ISO of 100. So, optimally,you should always try to stick to the base ISO to get the highest image quality. However, it is not always possible to do so, especially when working in low-light conditions.Typically, ISO numbers start from 100-200 (Base ISO) and increment in value in geometric progression (power of two). So, the ISO sequence is: 100, 200, 400, 800, 1600, 3200, 6400 and etc. The important thing to understand, is that each step between the numbers effectivelydoublesthe sensitivity of the sensor. So, ISO 200 is twice more sensitive than ISO 100, while ISO 400 is twice more sensitive than ISO 200. This makes ISO 400 four times more sensitive to light than ISO 100, and ISO 1600 sixteen times more sensitive to light than ISO 100, so on and so forth. What does it mean when a sensor is sixteen times more sensitive to light? It means that it needs sixteen times less time to capture an image!ISO Speed Example:ISO 100 1 secondISO 200 1/2 of a secondISO 400 1/4 of a secondISO 800 1/8 of a secondISO 1600 1/16 of a secondISO 3200 1/32 of a secondIn the above ISO Speed Example, if your camera sensor needed exactly 1 second to capture a scene at ISO 100, simply by switching to ISO 800, you can capture the same scene at 1/8th of a second or at 125 milliseconds! That can mean a world of difference in photography, since it can help to freeze motion.

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