Term

Explanation

Other References

Bayer Matrix

Because pixels are colour blind they are covered with a layer of filters called a Bayer Matrix. This has tiny green / red / green / blue filters which cover the sensor. The camera's on-board computer cleverly interprets the data as R G and B information.

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CCD

Charge Coupled Device - the sensor which is used in many digicams. It is a small, rectangular piece of silicon rather than a piece of film to receive incoming light. This silicon wafer is a solid-state electronic component which has been micro-manufactured and segmented into an array of individual light-sensitive cells called "photosites." Each photosite is one element of the whole picture that is formed, thus it is called a picture element, or "pixel."

Example 

CMOS

Short for complementary metal oxide semiconductor. Pronounced see-moss. Used increasingly in digital cameras to make the sensor. More sensitive and less energy dependent than traditional CCDs.

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CMYK

Stands for colours displayed using a additive mixture of the 3 complementary colours Cyan, Magenta and Yellow plus K = Black. Printers always use the three colours plus black to produce the final image. It is not, however, the right form in which to send colour photos to the printer - use an RGB colour space for that.

Answers.com

Colour

(1) of an object, aspect of object appearance distinct from form, shape, size, position, or gloss that depends upon the spectral composition of the incident light, the spectral reflectance of transmittance of the object, and the spectral response of the observer, as well as the illuminating and viewing geometry. 
(2) perceived, attribute of visual perception that can be described by color names such as white, gray, black, yellow, brown, vivid red, deep reddish purple, or by combinations of such names. 

Apogee Colour Temp chart

Colour Space

The range of colours handled by a device, e.g. computer, camera, scanner or printer is called a colour space. It contains all the colours that the device can comfortably handle.
Changing colour space is through the MODE command in Photoshop..

RGB, AdobeRGB, sRGB, LAB, CMYK
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Colour  Balance

The amounts of individual colours can be easily set using this image adjustment tool. It does not affect the brightness or saturation of the colours only the amount.

Digital Darkroom

Comparison to Film

Is digital better than film?

Tidbits Notes 

Compression

When a digicam takes a picture the majority of them process the data for exposure, white balance and sharpness. The resulting image file is then compressed and saved as a .jpg format file. The compression is selectable in most cameras and should for preference be kept to a minimum. Compression also takes place when a file is saved to the computer, then opened, edited and resaved as a .jpg file.

High compression
(set file to fit screen)
No compression

Curves

This is a means of adjusting the image similar to levels, but with much greater power. 

Digital Darkroom  
sphoto.com/#curves 
Example

Undithered Image

Dropper Tool

This can be used to check precise colours anyhere in the picture. It can sample single pixels or a 3*3 or a 5*5 average - which I prefer. You can then work on colour balance and monitor the changes numerically.

images/dropper-info-tool.jpg

Formatting

Normally a reference to either cleaning out a hard drive permanently or a memory card. It clears all data totally. It can also refer to the layout of a printed or web display page, a font selection etc.
For camera memory cards I recommend you use the camera's own formatting menu.

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Gamut

The range of colours displayable or printable. Photoshop can be set to show if colours are out of gamut, i.e. will not be printed. A bright saturated blue color displayed on your monitor for example may not be reproducible on your printer because your printer simply cannot make that color.  In this case, we would say that the example blue color is in the monitor's color gamut but outside the printer's color gamut.

Steve's Digicams - Tech Corner - July 2005

Histogram

A display which shows the ranges of tones present in a photograph. They can also show the range of the individual colours or channels. These are always seen when adjusting levels.

Example

Hue

The attribute of color by means of which a color is perceived to be red, yellow, green, blue, purple, etc. 
Pure white, black, and grays possess no hue. They are often used to remove any slight colour cast by using the white or gray droppers in the levels or curves dialogues in Photoshop

Example

jpg format

A compressed file format. When saving files as jpg the compression writes similar colour pixels as the same colour. This results in blocks of similar colour appearing. However you should only see this if you use heavy compression.
For best results, work only on a copy of the original photograph and save everything at maximum quality.  
New and much better versions of jpg formats are becoming available, e.g. JPEG 2000.

jpg = short for jpeg = short for Japanese Photographic Expert Group

DPReview.com DPReview.com(2)  
jpeg.org

LAB

Another colour space, of some value in digital photography. It was originally designed to be a machine independent colour space. The channels are Lightness, A, B where A and B contain all the colour information.

Answers.com

Layer

These are like transparent film lying over the photograph, with instructions to the program  on how to change the image. Layers can be switched on or off to check the effect. They do not make any permanent changes unless  they are flattened

Making a layer
Effect of curves layer 

LCD

LCD = liquid crystal display. This consists of two polarizing transparent panels and a liquid crystal surface sandwiched in between. Voltage is applied to certain areas, causing the crystal to turn dark. A light source behind the panel transmits through transparent crystals and is mostly blocked by dark crystal

How Stuff Works
DPReview

Levels

The levels dialogue is found in virtually all digital editing programs. It allows you to set values for black, white and gray mod tones, as well as correct the exposure for under-exposure, too pale shadows, and also adjust individual colours. 

Digital Darkroom
 Levels Diagram

Memory Card

Cameras require some means of recording data. The memory cards can run in size from 16 MB (very small) to sometimes 4 GB, ideal for professional cameras. There are several different types. You will always need to buy one because manufacturers hardly ever give you a decent one. Surprise surprise!

Types of memory cards include:
Compact Flash (CF)
Secure Data (SD)
Memory Stick (MS)
xD 
Other types are obsolete.

dpreview.com

Noise

Digicam sensors produce only very tiny signals which have to be amplified. Unfortunately they can also make a lot of noise, and this is also amplified. It is worst in low light, high ISOs and with smaller sensors! Like film grain it can destroy the pictures detail.

Example

Pixels

Cameras record photographs as pixels (picture elements). A digicam can have from 3 up to 15 mp in its sensor. However the number of pixels isn't as important as how the camer uses them!

dpreview.com

Pixels - Hot

A hot pixel is one that generates too high a signal. You take some long exposure night shots and are horrified to see a bright spot in the same part of every picture -- and it isn't a star. It's the infamous hot pixel! A hot pixel is created by an element with a higher rate of charge leakage than its neighbors which, on a long exposure, may cross the threshold of an exposed value. Many digicams don't permit exposures longer than a quarter second, which effectively eliminates the chance that any element with a dark current, so to speak, will consistently report an exposure value.

imaging-resource.com

Pixels - stuck

From time to time a recording site on a sensor will go wrong and always record as if hit by a bright light. This is called a hot pixel. Sophisticated cameras program these out by averaging the value of surrounding cells. Sometimes they have to be removed in Photoshop. It is well worth scanning your photo at about 300% to find them.

Example

RAW files

Professional cameras can record their photographs in a completely unprocessed format, called Raw. Nikon's raw files end in .NEF. This allows the photographer to  make changes to the contrast, colour balance, sharpening, etc. This data is recorded separately so that the orignal file is completely unaffecte. Unfortunately  these files are very large and are not usually produced on consumer cameras.

Luminous-Landscape.com

Resolution

Defines how much detail a camera or other device can capture and display. Whilst the number of pixels is important, so is the lens and the amount of noise generated by the pixels. Big sensors with big pixels are always better! If you are buying a digital compact camera, aim for a sensor 1/1.8", and around 6 mp. Try to get one with the most control over the exposure, quality of compression, etc.

Luminous-Landscape.com 

RGB

Stands for the 3 primary colours Red, Green and Blue. This is the basic colour space used by all cameras, software programs and printers. There are various varieties of RGB, the best known called AdobeRGB. Most cameras work with a limited form called sRGB but you won't see any difference. Always work in this colour space.

RGBHex Chart  

Saturation

The intensity of the colour in a photograph. This can be adjusted either globally or for selected individual colours in the Hue, Saturation, Lightness dialogues in Photoshop. All grays have zero saturation.

See Hue

Sensors

These make a tiny electrical signal to record the light and its colour when you press the shutter. They are made mainly by Sony. The sizes vary from about 0.5 cm² to 2.5cm by 3,5 cm. Very small sensors tend to make a lot of noise, especially when there is little light or the ISO is high. Generally big sensors are better than little ones.

DPReview.com  

Sharpening

This in fact is a trick of the eye!. Sharpening increase the local contrast between adjacent tones, forming a faint, thin line around it. As a result the two adjacent areas seem much more strongly separated and hence the picture looks sharper. Best results are, in my opinion, got by going into Photoshop's filter menu and selecting
Unsharp Mask
% set to 500 - very heavy sharpening
Radius to 0.5 pixels - actual spread very tiny therefore unlikely to be visible
Threshold to 3 or 4 - avoids sharpening low contrast areas such as skin.

dpreview.com

sRGB

This is a limited form of Adobe RGB designed originally to work with Web images but now almost universally adopted by digital cameras. Semi-professional cameras will offer a choice of colour space.

Shutterfly.com

tiff format

Tiff format records every single pixel in an image independently. There is no compression. However, although you keep all the data, the file sizes are very big. The file ending is usually TIF
TIFF = Targeted Image File Format

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Tint

Is the color produced by increasing the amount of white in a colour. The color of the resulting mixture is lighter and less saturated than the colour without the addition of the white.
A variation of a color produced by adding white, thus decreasing saturation and increasing lightness.

Wikipedia 

White Balance

The colour of light is affected by where it comes from. Thus midday sun is defined as neutral in colour. Sunset light is very orange, candles are reddish, whilst blue sky when the sun is hidden is very blue. To get the right balance, cameras use an auto white balance setting. However this is often unsatisfactory and in different light, especially tungsten bulbs, they get it totally wrong! You can usually choose the a setting to match the light source, but remember to change it back. Afterwards you can make minor changes in Photoshop.

Apogee Colour Temp chart dpreview.com/

White Balance Preset

The cameras own settings are often not enough, and by taking a blank shot of a piece of white or gray card you can tell the camera to use a user-defined setting. This is particularly useful when using studio lighting.

Cambridgeincolour.com