Digital Photography Jargon

Digital photography has now virtually replaced the usual SLR shoot to film camera. Digital photography jargon helps explain much of the mechanics involved with taking digital photographs for use with a computer.

Even computers are now becoming less reliant upon digital cameras as many printing systems have now evolved that allow you to print your digital photograph direct from the camera without ever downloading your photograph to a separate hard disc.

Much of the digital photography jargon also applies to the older slr camera such as shutter speed and aperture size. Many people think that digital photography is difficult to understand but as most fleet street hacks and the paperatzi these day use nothing but digital cameras, understanding the digital photography jargon cannot be that hard after all.

Media - Digital Photography

Aperture

Behind the lens of a camera is a movable circular iris which opens and closes much like the pupil of an eye to control the amount of light falling on the CCD. This is usually controlled by the light meter, although some of the cameras have a Manual Mode. Altering the aperture also changes the Depth of Field.

Aperture Priority

This is one of the semi-manual Exposure modes found on some cameras. The user sets the Aperture according to the Depth of Field they require, and the Metering System sets the Shutter speed to obtain the correct exposure.

Artefacts

When an image is stored in your camera's memory it has to be compressed to fit, usually in a JPEG File, and in the process some information is inevitably lost. When the image is uncompressed for viewing, noise creeps in and appears as angular blocks in the image, which are known as artefacts.

Auto Bracketing

Bracketing shots is where a photographer takes the same shot three times or more, each at different Exposures. This increases the chances of getting the ideally exposed image. Also it's possible to combine the shots in software to increase the light and shade (Dynamic Range) within the image. Some cameras have auto bracketing features to allow you to specify the amount of underexposure and overexposure that are used when using the Burst mode.

Auto Focus

Most digital cameras feature an auto-focus mode, by which electronics inside the camera examine the image, looking for edges and lines. They then adjust and focus the lens to make the lines as sharp as possible, all in a fraction of a second. Some systems also include a small lamp next to the flash which casts a grid pattern on to the subject for an instant to help the camera focus in low light.

AD Converter

The output from an image chip (CCD) in a digital camera is in the form of an analogue signal. This is converted into digital values by the built in analogue/digital converter in much the same way a MiniDisc or CD recorder would deal with the analogue input from an audio cassette. Ordinary digital cameras use 8-bit analogue-to-digital conversion, which means that each Pixel can represent up to 256 different values for brightness. Professional digicams offer 10-bit or even 12-bit conversion, which means the pixels can represent up to 1024 or 4096 brightness values respectively. This offers a far more accurate result and a noticeably clearer picture.

AE Lock

Stands for Auto-Exposure Lock, a function that is generally only found on more expensive cameras. This enables you to take a light meter reading from a particular part of the image and the hold that setting while you compose the image. Useful for dealing with Backlighting, and other difficult lighting situations.

Backlighting

Backlighting occurs when your subject is brightly lit from behind, such as someone standing in front of a sunlit window. Unless you adjust the Exposure to compensate for this, your subject will appear as a dark silhouette against the bright background. You may be able to sometimes compensate for this effect with editing software.

Burst

Many digicams offer a burst mode, which means you can take several images in rapid succession, just like you get with a motor wide on a traditional film camera. The amount of images that can be captured is limited by the camera's image capture and processing system, as well as the size of the internal memory buffer. You'll typically get around three frames per second from a standard digital camera on burst mode.

Centre Weighted Metering

This is when the camera takes an average light reading from the whole frame, but emphasises the reading from the central portion of the image. This has been largely superceded in digital photography by Multi-pattern metering, which is better able to cope with unusual situations.

CCD

Stands for Charged Coupled Device. This is the light sensor behind the lens of your camera; it records the image when you take a photograph. It consists of a grid of millions of tiny light sensors, one for each Pixel of the image. The size of the CCD is measured in Megapixels, and the higher the megapixel rating the better the image Resolution of the CCD.

CMOS ("see moss")

Stands for Complimentary Metal-Oxide Semiconductor. In the context of digital cameras this is a type of light sensor that often offers higher Resolutions than a CCD at a fraction of the cost. This technology has yet be fully exploited but is becoming common in SLRs (for example the Canon EOS 350D, EOS 1DS Mark II, and Nikon D2X).

Depth of Field

When you try to focus your camera on a subject, some detail behind and in front of the subject will also be in focus. The distance between the furthest and nearest details that are in focus is known as the depth of field. The depth of field can be changed by altering the size of the Aperture. The smaller the aperture the longer the depth of field.

Digital Zoom

Some cameras give you the option of zooming in on the central area of an image. Although the zoomed area looks bigger it still contains the same amount of Pixels it did originally, so it will appear blocky and will lack Resolution, particularly when printed. Not to be confused with Optical Zoom, which is far superior.

Dynamic Range

This is the difference between the lightest and darkest parts of the image. If an image has very bright highlights and very dark shadows, as well as everything in between, it is said to have a wide dynamic range. This can cause problems for some digital cameras.

DPI

Stands for Dots Per Inch. The sharpness of an image produced on a printer is defined by how many dots of ink per inch of printed paper its print head can produce. A figure of 180 DPI or higher is usually required for photo-quality results, most modern printers are capable of this.

Effective pixels

Though your digicam may claim to have 3.34 million Pixels on its CCD, some of the pixels will not be used for taking pictures. Usually those around the edge of the sensor are painted black to provide a colour balance, while others fall outside the range of the lens. Effective pixels are the ones actually used to capture the image.

Electronic viewfinder

Like a video camera, some viewfinders contain a miniature TV monitor showing what the camera sees. This usually uses less power than the LCD screen on the back of the camera, but can be a strain on the eye and difficult to focus.

Exposure

When you take a picture the light meter within the camera determines how long the Shutter should be open for and how wide the Aperture should be, thus obtaining the correct exposure on the CCD. If the picture is too dark, it is underexposed, whereas if it goes the other way and is too light, it is overexposed.

External flash

Some cameras feature a hotshoe connection, which enables the use of a flashgun other than the built in camera flash. This enables a lot more creative freedom and control over lighting, because the flash can be positioned further away from the camera. It also helps to prevent red-eye when taking portraits. This feature is only usually available on prosumer or SLR cameras.

EXIF

The Exchangeable Image File (EXIF) format is used by nearly all digital cameras that output images as JPEGs. It enables information, such as the date and time the shot was taken, plus Exposure and other camera information, to be stored in the image file alongside the normal image information. These details can then be read by photo archiving software such as ACDSee and Thumber, so you can get an instant view of exactly what your camera was doing when you took the shot; handy for troubleshooting and retaking.

Field of View Cropping

On most digital SLRs the capture device is smaller in size than a 35 mm negative, therefore the field of view provided by a lens is effectively cropped (in the case of the Nikon D70 the crop factor is 1.5x). This used to be referred to as 'focal length multiplier' although this term is actually inaccurate as it is not a multiplication but a crop, we prefer to refer to it as Field Of View cropping (or FOV cropping). An 18 - 70 mm lens, when used on a camera with a 1.5x FOV cropping factor, provides a field of view approximately equivalent to a 27 - 105 mm lens on a 35 mm film camera. This of course helps out those who have long zooms by making them longer but causes problems for those with wide angle lenses by decreasing their effectiveness by changing most of them to standard lenses.

Fixed Focus

Cheaper cameras have fixed-focus lenses, which cannot be adjusted. Instead they rely on a very narrow Aperture to make everything appear in focus, from a few feet in front of the camera to infinity. They're fine for snapshots at average distance in good light but are not so good for creative photographs where blurring can be used to produce unusual effects.

Focal Length

In brief, this term describes the magnifying power of the camera's lens. The longer the focal length the greater the magnification. Conversely, the smaller the focal length, the more wide-angle the lens.

f-number

The number which describes the ratio of the Aperture. Generally, a higher quality lens will have a smaller f-number, which means a wider maximum aperture, and thus more light entering the lens. See also Depth of Field for some more information about focusing.

Histogram

Generally a graph of brightness. It ranges from black through grey to white along the horizontal axis, while values in the vertical axis represent the number of Pixels at the appropriate brightness. It provides a means of checking the Exposure of the image. If too many pixels are present at the left-hand side of the histogram, it's likely that the image is underexposed while if it's weighted to the right then it's likely to be overexposed. A histogram function is built into some of the more sophisticated digicams so you can instantly see whether the exposure needs adjusting by looking at the graph.

Interpolation

Some cameras and image-editing software can increase the size of a digital image by adding extra Pixels in between the original ones. They take an average of the pixels around the new one and attempt to match the colour and brightness to create a seamless image. Some systems give better results than others.

ISO

Stands for International Standards Organisation. In conventional photography, the ISO number is a measure of the light sensitivity of photographic film, and this has been carried over into digital photography as a way of expressing light sensitivity of the CCD.

Jaggies

A slang term, maybe, but 'jaggies' refers to jagged diagonal lines that appear in a low Resolution image. Pixels are square, so if large pixels are being used to represent a diagonal, you'll be able to see the corners of each, creating a saw-like edge. Anti-aliasing is used to soften jaggies, whereby the software will attempt to calculate 'in-between' shades to blur the line a little and make it look smoother.

JPEG

Stands for Joint Photographic Expert Group, and is the most commonly used system of image compression. Using a sliding scale between file size and picture quality, it enables digital cameras and computers to squash a large picture file into a small amount of memory. Be careful when compressing files, though, because too much compression will reduce the quality of your image.

Landscape mode

A program Exposure option found on many mid-priced cameras, this function automatically selects the best exposure setting for landscape photographs, usually a longer Shutter speed and the narrowest Aperture to maximise Depth of Field. It can also refer to holding the camera horizontally, which is usually preferred for landscape shots.

LCD

Liquid Crystal Diode. Most digicams have an LCD screen mounted on the back for viewing photographs. Though useful for carefully composing vital shots and reviewing them afterwards, they can be a heavy drain on the batteries, so use them sparingly.

Li-Ion

Stands for Lithium Ion. Many digital cameras take a dedicated Li-ion rechargeable battery. They hold more power than other types of battery, and don't suffer from the 'memory effect', where a partially charged battery, when recharged, will only register the additional charge rather than its full capacity.

Macro Mode

Traditionally refers to a lens that can focus closer than its designated Focal Length, but these days it is used to describe any facility for taking extreme close-ups.

Manual Mode

Found on higher-end digicams, this is really for experienced photographers only. It gives full control over both Shutter speed and Aperture and therefore Depth of Field. An absolutely essential feature for imaginative and creative photography.

Megapixel

A measure of the size and Resolution of the pictures that a digital camera can produce. Mega means one million, and in this case a million Pixels, or more accurately a million individual light sensors on the camera's CCD. The more megapixels, the larger you can print your images without losing quality.

Memory card

Most digital cameras store your pictures electronically on removable cards full of computer memory, sometimes called 'digital film'. They come in a variety of sizes and there are several different formats, including Compact Flash, SmartMedia, SD (Secure Digital), Memory Stick, and xD-Picture cards. They all have certain advantages, but do exactly the same job.

Metering System

This is how the camera measures the amount of light being reflected by whatever you are trying to photograph, to determine the correct Exposure for that particular scene. Different types of metering used by digital cameras include Spot Metering, Multi-pattern metering and centre-weighted metering.

Microdrive

A Microdrive is a data storage system developed by IBM, consisting of a tiny hard disk in a package the same size as a Compact Flash Memory card. Microdrives can store large amounts of data, but on the downside can be fragile due to having moving parts.

Movie Mode

Movie mode is the ability to capture video clips on a stills camera. Normally the movie will be in QuickTime, AVI, MPEG formats or less commonly JPEG movie. The Resolutions and frames per second of these movies varies from camera to camera, high-quality being 30fps at 640x480 Pixels.

To capture movie it is important to note that normally a fast Memory card is required to prevent long download times and benefit from long movie capture times. (Lower resolution movies may not always require accelerated cards)

Fast cards are:

any xD-Picture card (3Mb/second)

IBM MicroDrive (3Mb/second)

Any CF or SD card that reports to have 3Mb + per second transfer rate, for example the Sandisk Ultra II range.

3Mb per second appears to be the standard that has been set and recommended to get full benefits when capturing movie.

Multi-pattern metering

This is a sophisticated means of determining the correct Exposure needed for an individual photograph. The camera performs multi-pattern metering by taking a number of light readings from several different areas of the frame and compares them to its pre-programmed data to determine the correct exposure. Multi-pattern metering is used to ensure that bright light sources, such as the sun or brightly lit windows, won't cause the rest of the image to be underexposed and appear dark in the final photograph.

Night-time mode

A program Exposure mode that compensates for low light by setting the Aperture to maximum. This lets the most available light into the camera and gives you the fastest possible Shutter speed available under the circumstances for maximum results in low light conditions.

Ni-MH

Stands for Nickel-Metal Hydride, a type of rechargeable battery rapidly replacing older Nickel Cadmium (Ni-Cd) batteries. Ni-Mh Batteries do not suffer from 'memory effect' which was a problem with the older rechargeables not operating at peak efficiency, and they can also store a lot more power. This makes them ideal for use in battery-guzzling digital cameras. Ni-MH AA rechargeables are a must for cameras which take AA batteries - a great money saver when compared to Alkaline batteries.

Optical Zoom

Many digital cameras have small but powerful optical zoom lenses. This means they can be adjusted to magnify the image (zoom in) or to capture a wide-angle shot (zoom out). Because the image uses the full capabilities that the CCD makes available, it is far preferable to Digital Zoom.

Pixel

Short for Picture Element. If you enlarge a picture on your computer, you will see that it is made up of tiny squares of a particular colour and brightness called pixels. A pixel is the basic building block of a digital photograph, and there can be several million of them in an image. The larger the pixel count, the larger you can print your image.

Portrait Mode

This is a program Exposure mode that optimises the camera for taking classical portrait shots, widening the Aperture to minimise the Depth of Field. This ensures that only the subject is in focus, while the Shutter speed is increased to minimise camera shake.

Program Exposure

Found on most digital cameras, programme Exposure is an automatic setting by which the camera's Metering System selects an appropriate Aperture setting and Shutter speed in an attempt to get the best exposure and performance out of the lens.

RAW

Most digital cameras use the JPEG file format, one that most PC users will have encountered before. JPEG is a compressed image file enabling more images to be stored in memory, but at a loss of quality. RAW is the raw data from the image sensor before any processing is applied. In essence, it is a true representation of what the image sensor has seen. It is lossless and can capture data up to 12 bits, which is better than typical JPEG and TIFF formats. On the downside, a RAW file takes a great deal longer to process. Many prosumer and SLR cameras can save images in RAW format.

Resolution

The more Pixels there are in an image, the larger you can print it. Resolution is usually expressed as two numbers representing the height and width of the image in pixels, such as 2048 x 1536. A simple sum can be used to calculate optimum print size for any given resolution; when printing at 180DPI for instance, a 2048 x 1536 image can be printed at 11.37 x 8.53 inches (resolution width or height/required DPI=maximum print width or height).

Shutter

The shutter is the device behind the lens of the camera which is normally closed, but opens for an instant when a picture is taken to allow light into the camera and onto the CCD. The length of time the shutter is open is for is determined by the Metering System, and is known as the shutter speed, not to be confused with shutter lag. You will find that this will vary from shot to shot dependent on lighting conditions.

Shutter Lag

This is a problem found on many digital cameras. There will often be a slight delay between depressing the shutter release button and the camera actually taking the shot. The latest digicam designs have reduced this problem a great deal. This problem is normally overcome when half depressing the Shutter button whilst composing the shot, this will lock the focus and preset the shutter speed on most models thus making the lag virtually nil when you finally take the picture.

Shutter Priority

This is a semi-Manual Mode that enables the photographer to specify a Shutter speed while the camera's Metering System sets the Aperture for the correct Exposure. It's useful if you want to take action shots using a faster shutter speed or intentional motion blurred shots with a slower shutter speed.

SLR

Stands for Single Lens Reflex. A mirror or prism reflects light coming in through the lens to the viewfinder, so when you look through it you see exactly what the camera sees. This is very useful for framing your pictures accurately. It is only found on a few of the most expensive digicams, although is standard on many professional film cameras.

Spot Metering

Found on the more expensive cameras, this metering mode enables the photographer to take a particular light reading from a small area on the middle of the frame, usually marked in the viewfinder. This is the best way with dealing with difficult lighting conditions such as Backlighting, and is normally used in conjunction with auto-Exposure lock.

Thumbnail Index

Many Graphics programs that photographers commonly use on a PC or Mac can look at all of the pictures in a given folder and display them as a page of smaller images. These are known as thumbnails, and clicking on the thumbnail will usually display the full-sized image. Examples are Piccolo, Paint Shop Pro and ACDsee.

Time Lapse

We've all seen films of flowers opening at incredible speed, or the sun and clouds racing across the sky. This super fast motion technique is called time-lapse photography, whereby a stationary camera takes several successive shots at time intervals of a few seconds, minutes or even hours. The images are then played back rapidly, giving the impression of continuous motion. Some digital cameras have a time-lapse mode, while others require you to fire the Shutter manually. Definitely a photographic technique for the patient.

VGA

Stands for Video Graphics Array, and is the lowest Resolution that computers will use to display an image. The picture size is 640x480 Pixels, and is used by many cheaper digital cameras and web cams. Some digital cameras use even smaller image size called half-VGA, which is 320x240 pixels. Both these sizes will only print to photographic quality at a very small size.

Webcam Mode

Some cheap low-Resolution digital cameras, usually those limited to VGA images, can be connected to a computer, and thereby to the internet for use as a Webcam for live video conferencing over the Internet. They're also ideal for use when chatting to friends on the Web.

White Balance

Most modern digital cameras will automatically adjust the colour balance of the picture as a matter of course - to compensate for any tints in the ambient light, such as sunlight, florescent strip lights or normal indoor light bulbs. This is called White Balance, and means you can take a picture indoors without the resulting orange tint that you often get with a film camera. White balance can also help with improving general picture quality when taking pictures in a gloomy setting.

USM

USM stands for Ultra Silent Motor, this simply means that the lens will focus more quietly than a non-USM lens.

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