Digital Photography Jargon? Easy!

Digital Photography Jargon? Easy!

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Got your bits mixed up with your bytes? Is a halftone less than a semi-quaver? Computer terms can often be a mess of confusing jargon. Lets’ try to make it easy with some photography definitions and the start of a glossary. Feel free to let us know what other terms that you’d like covered in comments below.

BIT MAP IMAGE

An image with 1 bit of colour information per pixel is also known as a bit mapped image. The only colours displayed in a single bit mapped image are black and white. Adding bit depth allows the rendering of more colours.

Photoshop deals with bitmap images.

BRIGHTNESS

One of three dimensions of colour; the other two are hue and saturation. The term ‘Brightness’ is used to describe differences in the intensity of light reflected from or transmitted through an image independent of its hue and saturation.

CMYK

The four process colours used in printing: cyan, magenta, yellow, and black (K).

CMYK IMAGE

A four channel image containing a cyan, magenta, yellow, and black channel. A CMYK image is generally used to print a colour separation; it is also the way that inkjet printers output colour images, taking the original RGB image and translating it in the printer.

COLOUR CORRECTION

The changing of the colours of pixels in an image, including adjusting brightness, contrast, mid-level greys, hue and saturation to achieve optimum printed results.

COLOUR PROOF

A representation of the final printed product, for checking colour accuracy and other elements.

COLOUR SEPARATION

The process of splitting full-colour artwork into its CMYK components; one or all four of the separate pieces of film from which a four-colour version will be printed.

CONTINUOUS TONE IMAGE

An image containing gradient tones from black to white.

CONTRAST

The tonal gradation between the highlights, mid tones, and shadows in an image.

DPI

Dots per inch: a measure of image resolution.

FOUR COLOUR PROCESS PRINTING

The basic method of recreating a broad spectrum of colours on a printing press.

GREY SCALE IMAGE

An image consisting of up to 256 levels of grey, with 8 bits of data or more per pixel.

HALFTONE

The reproduction of a continuous-tone image, made by using a screen that breaks the image into various size dots.

HIGHLIGHT

The lightest part of an image, represented in a halftone by the smallest dots, or the absence of dots.

HUE

The main attribute of a colour that distinguishes it from other colours.

IMAGE RESOLUTION

The amount of data stored in an image file, measured in pixels per inch (ppi).

JPEG

Joint Photographic Experts Group. This group established a standard method for compressing and decompressing digitised photos or images. Virtually all digital cameras can save images in JPEG.

LPI

Lines per inch: a measure of resolution, usually screen frequency in halftones. Applies to four colour reproduction in magazines and newspapers.

It indicates how close together the lines in a halftone grid are. A higher LPI figure indicates greater detail and sharpness. Offset printing, as used in newspaper production, usually ranges from 85-133 LPI. High quality colour magazines can go to 300 LPI.

LUMINANCE LIGHTNESS

The highest of the individual RGB values plus the lowest of the individual RGB values, divided by two; a component of a Hue-Saturation-Lightness image.

MID TONE

Tonal value of a dot, located approximately halfway between the highlight value and the shadow value.

MOIRÉ PATTERN

An unwanted and undesirable pattern in colour printing, resulting from incorrect screen angles of overprinting halftones. Often seen in images of certain fabrics and television images of a line pattern. Moiré patterns can be minimised with the use of proper screen angles.

In digital photography unwanted moiré patterns can be removed in software.

PIXEL

A single dot on a computer display or in a digital image.

PICT

An early file format for saving graphics or image information.

PPI

Pixels per inch, a measure of the resolution of a computer display or digital image.

PRINTER RESOLUTION

The amount of detail a printer will reproduce, measured in dots per inch (dpi). There is native resolution and interpolated resolution: the former indicates the true resolution of the printer or scanner; the latter is a function of software and detail is added artificially.

PROCESS COLOUR

The four colour pigments cyan, magenta, yellow, and black used in colour printing.

RAW FORMAT

A relatively recent method of capturing digital images. A RAW image file contains processed data from the image sensor of a camera. It consists of data written to the camera’s memory and needs to be interpreted by specialised software, then re-saved in a normal format, like JPEG or TIFF.

The benefit of RAW is that it is closest to the original image and uncompressed. The disadvantages are that a RAW file is much larger.

A RAW image is usually closest to the original picture in the sense that it preserves exactly what the camera’s sensor captured.

RESAMPLE

To change the resolution of an image. Resampling down discards pixel information in an image … the image remains sharp; resampling up adds pixel information through interpolation… sharpness can suffer.

RESOLUTION

The number of pixels per inch in an image, or the number of dots per inch used by an output device.

RGB

Red, green, and blue: the additive primaries. RGB is the basic additive colour model used for colour video display, as on a computer monitor.

SATURATION

The amount of grey in a colour. More grey in a colour means lower saturation; less grey in a colour means higher saturation.

SCREEN ANGLE

The angle at which the halftone screens are placed in relation to one another.

SCREEN FREQUENCY

The density of dots on the halftone screen, commonly measured in lines per inch (lpi). Also known as screen ruling.

SHADOW

The darkest part of an image, represented in a halftone reproduction by the largest dots.

THUMBNAILS

Miniature pictures, resembling slides, used in computer displays to indicate the contents of a graphic file.

TIFF

Tagged Image File Format, a file format for exchanging bit mapped and grey scale images among applications.

VECTOR IMAGE

A method of creating images with the use of geometric points, lines, curves, shapes and polygons.

A vector graphics program uses mathematical formulae to construct the image. There is no limit to the final sized of the image, unlike bitmap images.

Adobe Illustrator creates vector images.

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Barrie Smith is an experienced writer/photographer currently published in Australian Macworld, Auscam and other magazines in Australia and overseas.

Some Older Comments

  • Jack Fussell April 15, 2009 08:25 am

    thanks for the list

  • JohnB April 15, 2009 05:08 am

    @pkson, the 'key' effectively "means" black, so you're both right.

  • PKSon April 11, 2009 08:29 pm

    CMYK stands for Cyan, Magenta, Yellow, and "Key," doesn't it?

  • myke phillip April 11, 2009 05:52 pm

    thanks for this useful and easy reference you provide me .. keep it up.

  • Scott April 10, 2009 11:09 pm

    Great start, though I would suggest links (or expansions) to more in-depth explanations, for at least a few of the topics.

  • Dennis Newman April 10, 2009 10:20 am

    This is probably simple, but I'd like to see a detailed explanation of "layers" as used in Photoshop.

  • katrina April 10, 2009 07:19 am

    question for all, i am having trouble learning the metering mode on my camera, what do they mean? and which mode is best for what type of photo? what is the difference between them all? I have a canon 40D

  • JohnB April 10, 2009 05:52 am

    I think "tone mapping' is another term worthy of inclusion.

    It's amazing how, if you're in this any length of time, one can lose perspective on what terms with which "everyone" is, or is not really familiar. Try to recall how hard you had to dig in order to figure out what a particular word or acronym meant. If it wasn't readily apparent to you, it probably won't be to someone else, either.

  • Colin April 10, 2009 02:21 am

    A generous effort, thanks. "Continuous tone image" is incorrect, though. You describe it as an image containing gradient tones from black to white. What about color? And the whole idea is that each dot or pixel can be any color rather than just a few (like CMYK) that are dithered or half-toned to simulate a color.

  • Frahat Al Harthy April 9, 2009 04:28 pm

    Thank you so much this is really useful stuff...

    Thisngs to include:

    Chromatic Aberration
    Purple Fringing
    DGN

  • Dave April 9, 2009 11:48 am

    I'm thinking dynamic range should be included in this list.

  • Sherri Meyer April 9, 2009 10:36 am

    Excellent post. I will be sure to pass it along!

  • Matt Bamberg April 9, 2009 10:24 am

    How about a hard drive that stores 1 PETABYTE of storage space for your photographs?

    Matt Bamberg,
    Author http://www.amazon.com/Quick-Secrets-Create-Winning-Photographs/dp/1598639021

  • Mike April 9, 2009 10:05 am

    I'd like to take exception to two of your Jargon entries.

    DPI is he number of dots (pixels) PRINTED per inch. It has nothing to do with the resolution of the original image.

    Image resolution: The first half of your explanation is correct, but has NOTHING to do with pixels per inch. You could take a .640x480 image and "print" it at 1-DPI, and get a printed image 53.33' wide x 40' high. or print it at 72 DPI and have a printed image 8.8" x 6.6".

    You may have seen huge signs, or will soon that really have the same Image Resolution as an image on paper, but it will be designed to be viewed from across a ball field or hundreds of feet off the road. At the correct viewing distance they will look just as good.

  • jeffrey byrnes April 9, 2009 08:16 am

    I think this is a great list that could clear things up for people that are just beginning their education in photography.