Glossary of Digital Photography Terms

The following glossary is not a precise technical definition of terms, but instead is an attempt at explaining photography terms in simple layman's language.

Term Explanation

35mm Equivalent

Crop Factor
Focal Length Multiplier)

see Crop Factor


A camera mode that attempts to use a fast enough shutter speed (by upping the ISO) to prevent camera shake.

Using a higher ISO usually results in higher noise in your images.

Do not confuse with "anti-shake" or "image stabilization" technology where either the lens or CCD image sensor is stabilized to prevent camera shake.


Image Stabilization
Vibration Reduction)

A technology that stabilizes either the lens or image sensor to effectively reduce blur due to camera shake when using a slow shutter speed.

This allows the hand-holding of a camera at slower shutter speed (without upping the ISO).

Do not confuse with "anti-blur" or "picture stabilization" where the camera selects a higher ISO to allow the use of a fast enough shutter speed to counter the effect of camera shake.

Aperture Also refered to as f/stop, f/value, aperture value. The size the lens opens to allow in light. A large aperture is denoted by a small number, e.g. F1.8, while a small aperture is denoted by a large number, e.g. F16. A " fast " lens is one with a large maximum aperture.
Aperture-Priority Select an aperture (f/stop) and the camera chooses the best shutter speed. Use this mode to control the depth of field, e.g. select a small f/stop for landscape photography to ensure maximum depth of field, and a large f/stop for portrait photography to throw everything, except the subject, out of focus.
Boke (pronounced BOH-KEH), and increasingly referred to in print as "Bokeh" Japanese word meaning "fuzzy" and referring to the out-of-focus (OOF) portions of a picture. A lens is said to have "good boke" if the OOF is pleasant and does not detract from the main subject. A lens with good boke produces out of focus smooth-edged highlights and reproduces an out of focus point of light as bright in the middle and progressively getting fainter with a fuzzy edge.
Bulb (shutter speed) When set to the Bulb setting, the shutter remains open as long as the shutter release button is depressed. This allows for real night photography, and is ideal for taking multiple bursts of fireworks on one frame.
Crop Cropping a picture simply means to cut out a portion of the picture. For example, you may have extraneous details in your picture you do not want to display or print, so you "crop" it out. Notice, no enlargement is performed when you crop a picture. Often, you will read the term "100% crop" and all it means is that the photographer does not want to post the complete picture (could be 3MB+ in size) and so crops out the relevant part and post that as a "100% crop." No enlargement or reduction performed.

Crop Factor

Focal Length Multiplier
35mm Equivalent)

Not to be confused with "Crop" of a picture, these terms are exclusively used in the context of relating focal length to field of view (FOV), using a full-frame sensor size (24x36mm) as a reference.

When a 35mm lens is used on a digital SLR using an image sensor that is smaller than full-frame, the smaller sensor records only a "crop" of what a full-frame sensor can, thus recording a narrower field of view.

For example, an APS-sized image sensor is about half-frame and therefore has a crop factor, or focal length multiplier, of 2x (more accurately, 1.6x).

The term focal length multiplier is commonly used because, to obtain an accurate indication of the actual field of view covered, we multiply the 35mm focal length of the lens by the crop factor (focal length multiplier) to obtain a 35mm focal length equivalent.

Technically, lenses made specifically for a smaller than full-frame image sensor has no crop factor. Thus, we don't specifically speak of a crop factor for P&S cameras.

However, because image sensors in P&S cameras come in many different sizes, the specified focal lengths of the lenses do not accurately represent the actual field of view recorded and cannot be directly compared one to another. They do not really make any sense until we can relate all of them to a standard reference. By using a full-frame sensor and the lenses made for them as our reference, we can then assign a "35mm Equivalent" focal length to each lens/sensor size combination to obtain an accurate indication of the field of view covered.

Using "35mm Equivalent" focal lengths, a 35mm-50mm lens is considered normal (35mm is a slight wide-angle, but pretty much the norm in today's P&S cameras), a 28mm or less is a wide-angle, a 100mm-200mm is a medium telephoto, a 300mm-400mm (and longer) is a long telephoto.

Depth of Field The distance wherein objects are in focus. The smaller the aperture, the greater the depth of field achieved.
Exposure (Control) The different modes the camera provides for controlling exposure, e.g. Auto, Manual, Shutter Priority, Aperture Priority. See also: Shooting Modes.

Focal Length Multiplier

Crop Factor
35mm Equivalent)

see Crop Factor
Image Sensor

The image sensor is the equivalent of 'film'.

An image sensor contains millions of pixels (megapixels) arranged in a matrix whose job is to catch and record light when you take a picture. Each pixel registers the brightness -- or, intensity -- of the light falling on it. By using colored filters and an array of small lenses, the image sensor is able to record color values in a small footprint.

A high resolution image sensor (3 megapixels and up) can capture much more variation in light than a low resolution image sensor (less than 3 megapixels), and can therefore reproduce an image more faithfully and realistically.

We recommend an image sensor with a resolution of 3 effective megapixels and up .

The size of an image sensor also contributes to the quality of the images captured. In general, the larger the image sensor, the less noise in the images. So, all things equal, a 1/1.8 in. 4 megapixels image sensor will capture less noisy images than a 1/2.7 in. 4 megapixels image sensor.

Image Stabilization

Vibration Reduction)

see Anti-Shake

Light Metering

How the camera measures the amount of light available to expose a picture.

Centre-Weighted: Readings are taken at various part of the picture, with a special emphasis for the centre.

Spot: Readings are taken at a specific point.

Besides the above two light metering options, each camera manufacturer has its own variations, such as Matrix Metering, Multi-Pattern Metering, etc.

Macro Photography Photographing small objects, by usually moving close up. A steady tripod and a macro ring light ensure well exposed pictures. 

Megapixels, effective

Millions of pixels (usually used in reference to the resolution of an image sensor).

A digital camera can have an image sensor that is rated 4.2 megapixels but delivers an effective resolution of 4.0 megapixels. The higher the effective resolution, the higher the quality of the picture that can be recorded (providing the lens is able to produce the quality image in the first place).

Some digital cameras might advertise the "interpolated" pixels. As an example, Fujifilm's Super CCD image sensor can capture "effective" pixels of 3.1 megapixels, then its software kicks in and interpolates them up to 6 megapixels. Do bear in mind a digital camera that outputs 6 interpolated megapixels will never deliver the same quality that a real 6 effective megapixels digital camera will, and should still be compared to a 3 effective megapixels digital camera.

What is important when comparing resolution of different image sensors in digital cameras is the effective megapixels.


Original Equipment Manufacturer.

While this is not technically a digital photography term, you may have come across it when reading about how many of the major digital camera companies do not actually make the cameras bearing their brands, and wondered if one brand was any different from another.

The questionis sometimes yes and sometimes no.

The OEMs outsource the manufacture to those low-cost third party manufacturers and then rebrand the cameras, sometimes adding value in the form of better lenses and firmware and sometimes not.

Now you know why some of these digital cameras have very similar features set (especially the image sensor characteristics) and why they even look the same, minus some cosmetic changes.

Noise reduction

When a slow shutter speed is used (1/30 sec. and lower), the image degrades due to the buildup of electronic signal ("noise"). Software in the digital camera automatically compensates to reduce that noise. What is important is a camera with noise reduction that starts at shutter speeds of 1/30 sec. and lower .

Similarly, when a high ISO is used, noise starts to show in images. For now, most consumer digital cameras are not good at high ISOs, even though the camera might offer them.

Photoshop An image editing software. The most popular. 
P h o t o x e l s

Photo graphy + Digital Pi xels

Digital Photography is a marriage of traditional photography (you still gotta develop an eye for what makes a good picture) and digital pixels, hence:

Digital Photography = Photo graphy + Digital Pi xels = Photoxels .

Pixel Picture element.
Pre-focusing A technique to allow you to focus on a subject that is not at the center of the screen. By default a camera will focus at the center of the screen. By pressing the shutter release button half-way you can lock focus on your off-center subject, then recompose and depress the shutter release fully to take the shot.
Resolution, Sensor

For our purpose, let's just define this as the number of pixels used to capture an image. In reality, excellent image resolution is achieved by a combination of pixel count (image sensor resolution) and lens resolution.

If the image sensor resolution is expressed as numbers such as 2048x1536, just multiply them out and divide by 1 million to get the resolution in megapixels. In this case, we get 3+ megapixels.

Usually the higher the image sensor resolution, the better the image quality.

Shooting Modes

The amount of control you have in choosing how your digital camera captures an image.

All digital cameras usually have an Auto mode: the camera decides for you the best shutter speed/aperture settings.

Shutter Priority: Allows you to decide the shutter speed (e.g. fast at 1/500 sec. for stop action photography, or slow at 2 sec. for night photography), and the camera decides the best aperture.

Aperture Priority: Allows you to choose the aperture (e.g. large at F1.8 for portrait, of small at F16 for landscapes).

Manual: You have complete creative control in selecting both the shutter and aperture.

Scene Modes: Pre-set exposure control (shutter/aperture combination, plus other adjustments, such as white balance, exposure compensation, etc.) for various common picture situations, such as Night Scene, Portrait, Landscape, Action, etc.

Shutter Lag

The time elapsed between pressing the shutter release button and the camera actually taking the picture.

A short shutter lag (around 1/2 sec. or less) is desirable since it allows you to take candid shots.

A long shutter lag (around 1 sec. or more) means that you will find it difficult to capture the picture at the exact moment you desire (since the camera takes it one second or more after you depressed the shutter).

Shutter-Priority Select the shutter speed and the camera chooses the best aperture. Use this mode to freeze fast moving action or emphasize motion. For example, select a fast shutter speed (e.g. 1/1,000 sec.) to freeze a cyclist zooming by. Or, select a slow shutter speed (e.g. 1/30 sec.) to capture the cyclist as a blur to emphasize the speed of the motion. 
Shutter Speed The amount of time the shutter blades stay open to allow light into the camera. The longer the shutter stays open (e.g. 1/30 sec.), the more light; the shorter the shutter stays open (e.g. 1/1,000 sec.), the less light. Snapshots and action photography usually requires a fast shutter speed to freeze action; landscapes usually requires a small aperture for maximum depth of field, and hence a longer shutter speed for properly exposed pictures.
Storage Media The digital medium that replaces film. A number of competing storage media cards are offered, with the most common ones being CompactFlash (CF) and SmartMedia. [Sony uses its own proprietary Memory Stick, Olympus has introduced its proprietary xD-Picture Card.]

Vibration Reduction

Image Stabilization)

see Anti-Shake

White balance

When a digital pictured is captured, it can be manipulated, either using a image editing software (such as Photoshop) on your computer, or right at the time of taking the picture in the digital camera. White balance refers to the ability to adjust colors based on white as a reference color to give as true a white as possible; in the process, all the other colors are also corrected. Some preset white balance settings are daylight, cloudy, tungsten, or fluorescent. Using white balance properly is essential in digital photography.

Zoom, Optical vs. Digital vs. Total

Whereas an optical zoom uses the optics (lens) of the digital camera to move you closer to your subject, a digital zoom simply uses the existing image and enlarges it digitally.

Enlarging the image digitally reduces picture quality, and should therefore usually be avoided. However, a judicious use of digital zoom may sometimes yield images that are of quite acceptable quality. So, use with caution.

Some manufacturers label their lenses with the "total zoom" by multiplying the optical with the digital. Ignore total zoom claims because you can use any multiplier digital zoom you want in an image editing software.

What is important when comparing digital cameras is the optical zoom. Digital zoom can always be achieved later in an image editing software, such as Photoshop, so should not really be a determining factor when choosing a digital camera.