Stock photo usage - a glossary of useful terms

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Stock photo usage - a glossary of useful terms

Calibration

This refers to the process of setting a device to known colour conditions. Calibration must be performed externally for devices whose colour characteristics change frequently, e.g. monitors because phosphors lose brightness over time, and on printers because proofers and other digital printing devices can change output when colorant or paper stock is changed. Calibration is not required for most input devices (e.g., scanners and cameras) since these devices are generally self-calibrating. If your monitor and printer have been properly calibrated you can expect the stock photo you chose online will look the same as the final print. Calibrating a monitor includes adjusting its settings to compensate for the conditions you are working in (i.e. some monitors are viewed in natural light, others under artificial light), and ensuring that your computer has the correct colour settings for the printer. If the monitor you use for finding stock photos cannot be accurately calibrated (perhaps because your printing is a handled by a third party), you should add a step to your final image selection process that includes viewing the images on a calibrated monitor.

CMYK

Stands for cyan, magenta, yellow and black which are the four so-called process colours that are used in four-colour printed printing (often miscalled 'full colour printing' which is completely wrong as there are printing methods that use more colours to get more precise results). They represent the subtractive colour model, where a combination of 100% of each component yields black and 0% of each yields white. Cyan, magenta, and yellow are the subtractive complements of red, green, and blue respectively.

Whereas RGB monitors emit light, inked paper absorbs or reflects specific wavelengths. Cyan, magenta and yellow pigments serve as filters, subtracting varying degrees of red, green and blue from white light to produce a selective gamut of spectral colours. Like monitors, printing inks also produce a colour gamut that is only a subset of the visible spectrum, although the range is not the same for both. Consequently, the same stock photo displayed on a computer monitor may not match to that printed in a publication. Also, because printing processes such as offset lithography use CMYK inks, a stock photo, which is usually supplied as RGB to give the designer, must be converted to CMYK colour to enable use. When the conversion takes place, colour shifts can occur on RGB colour that has no CMYK representation (and is therefore compressed to fit the model). When this colour compression happens, there are inevitably going to be colour shifts (particularly in the intense Reds, and Greens) which is why it's important to choose a supplier that has experience of dealing with this process.

Characterization

This is the process of creating an ICC profile that describes the unique colour characteristics of a devices used to process your stock photo, such as a monitor, scanner, colour printer, and printing press.

Comping image

A low resolution stock photo used for non final layouts.

Continuous tone

A continuous tone results when a stock photo has not been screened and contains gradient tones from highlight to shadow. The original can be either black and white or colour and contain no dots.

Convergence

This occurs in an RGB monitor, where red, green and blue signals all "converge" in one pixel. At full brightness, the RGB pixel in convergence would be white.

Digital proof

This is a proofing system that does not include the use of film. Data is sent to a printer and imaged directly onto a paper-based material. There are several limitations of a digital proof: 1) they do not use the film that will be used to produce plates, and thus are open to interpretation of the output device, 2) few of these devices print in the same dot pattern as is utilized in the printing process, and 3) the ink utilized in these printers is not representative of the inks used in the printing process and can show a vast colour range and density not attainable on a printing press. Digital proofs are usually used where money or time is too much of an issue to run a wet proof.

Dimensions

Height and width, measured in centimetres or inches that a stock photo should be output at. Height is generally given first in Europe but the opposite is true in the US. CHECK THIS

DPI

Stands for dots per inch. This measures the resolution or the number of dots in a stock photo that a printer can print or the number displayed on a screen per inch both horizontally and vertically, and therefore is also an indicator of quality of output. As an example, a 600 dpi printer can print 360,000 (600 by 600) dots on one square inch of paper.

Halftone

When a stock photo is looked at through a screen that converts the image into dots of various sizes. When printed, the dots merge to give an illusion of continuous tone to the naked eye.

HSB

This stands for hue (the pigment); saturation (the amount of pigment) brightness (the amount of white included) in a coloured stock photo. With the HSB model, all colours can be defined by expressing their levels of hue, saturation and brightness in percentages.

ICC device profile

This is a file that describes how a particular device reproduces a stock photo's colour. It does this by transferring the critical information that the devices need regarding the intended colour levels of the output. Generic profiles are created by the device manufacturer, who examines the colour characteristics of a group of the same devices under controlled conditions, and then use this information to create a profile.

Gamut

This means every colour combination that is possible to produce with a given set of colourants on a given device or system.

Imposition

This is the process of laying out pages in a press form so that they will be in the correct order after the printed sheet is folded.

Interpolation

The process of increasing the resolution of a stock photo

JPEG

Stands for Joint Photographic Experts Group and is the most common compressed standard for high resolution stock photos.

Line Screen

This is the resolution of a halftone, expressed in lines per inch.

License

We don't sell images to you; we license them on behalf of the photographer or stock photo library. The license or reproduction fee that you are charged will cover specific uses you make of the image unless it is royalty-free, in which case the price is fixed. The license to use that image is granted upon payment of the fee. If you use the image for a purpose beyond the license, then further permission must be sought from Alamy or you will be in breach of your terms and conditions.

Lo-res

This is short for low resolution. If you use a lo-res stock image it will result in low quality reproduction because of a small number of dots or lines per inch.

LPI

This stands for lines per inch and is a measure of resolution for halftones

Model release

This is a signed release from the person/s depicted in a stock photo, giving consent for his or her likeness to be used for commercial purposes as described in the release. It is your responsibility to ensure that you have the correct model releases for your licence use and that you comply with the relevant local laws. For more information see our release information page.

Page formats

The standardised sizes used across the industry are as follows.

Use	Millimeters	Inches
AO print	841 x 1189	33 1/8 x 46 3/4
A1 print	594 x 841	23 3/8 x 33 1/8
A2/SRA2 print	420 x 594	16 1/2 x 23 3/8
A3 print/wraparound A4/ad	420 x 297	16.54 11.69
A4 print/ad	210 x 297	8.25 x 11.75
B5	176 x 250	6.93 x 9.84
Quarto print	254 x 203	10 x 8
American Quarto print	280 x 216	11.5 x 8.5
A5 print/ad	210 x 148	5.83 x 8.25
A6 print/ad	105 x 148	4 1/8 x 5x 7/8
Magazine - Broad	254 x 305	10 x 12
Magazine - Narrow	206 x 276	8.125 x 10.875
Magazine - Standard	213 x 276	8.375 x 10.875
Magazine - Wide	229 x 276	9 x 10.875
Periodical	260 x 330	10.25 x 13
Tabloid	279 x 432	11 x 17
CD cover	NEED SIZES
Web page - full screen/presentation		8 1/2 X 11 inch page
Web page - anything smaller than full screen	148 x 210	5.827 x 8.267

PANTONE Colours

A colour system of over 1200 standard colours developed by Pantone, Inc. The PMS Pantone Matching System is a swatch book that describes colours by assigning them numbers.

PICT

A stock image file format developed by Apple Computer, Inc. for use on Macintosh computers. The PICT format is adequate for storing and displaying data at 72 dpi, using the Macintosh screen, but is not sophisticated enough for higher-quality work.

Pixel

This is an acronym for Picture Element. When an image is defined by many tiny dots, those dots are pixels. A pixel represents the smallest graphic unit of measurement on a screen. The actual size of a pixel is screen-dependent, and varies according to the size of the screen and the resolution being used.

Pixelated

This refers to an image that is of poor quality because the balance between resolution of the image and the output is not correct, e.g., if 72dpi images are enlarged by 200% without using proper upsizing processes, such as interpolation. If this happens, the monitor would display each pixel of the stock photo spread out over 2 pixels of the monitor's resolution so the naked eye can distinguish the pixels in it, giving a jagged effect.

Process Colour Printing

Refers to the re-creation of colour by combing two or more of the cyan, magenta, and yellow colours, plus black.

Property release

This is a signed release from the owner/s of property depicted in a stock photo, giving consent for the image depicting his or her property to be used for commercial purposes. It is your responsibility to ensure that you have the correct property releases for your licence use and that you comply with the relevant local laws. For more information see our release information page.

RGB

Computer monitors and TVs emit colour as RGB (red, green, and blue) light. Although all colours of the visible spectrum can be produced by merging red, green and blue light, monitors are capable of displaying only a limited gamut of the visible spectrum. Abbreviation for red, green, blue; the colours used in displays and input devices. They represents the additive colour model, where 0% of each component yields black and 100% of each component yields white. Red, green and blue are the additive complements of cyan, magenta, and yellow respectively. Most stock images are supplied as RGB

Raster Image

This is an image displayed as a series of lines of dots or video 'blips'. When used in relation to a stock photo, it could refer to an image that has been used at the wrong resolution (see pixelated)

Resolution

This is a measure of stock photo output capability (depending on the fineness or coarseness of the digitized stock photo), usually expressed in dots per inch (dpi). It also measures of halftone quality, usually expressed in lines per inch (lpi).

Rights protected

This is a term used for exclusive usage of a traditionally licensed stock photo. Rights protection can be an advantage for high-profile projects as it can guarantee some exclusivity. The buyer obtains exclusive use of a stock photo under the terms of the license. These terms may affect the use, media, territory and/or duration in which the stock photo can by used by other buyers. Total protection can be offered to coverall these terms. Pricing for this type of license varies depending on the terms requested. Customers of Alamy would typically pay between 20-30% more to guarantee an exclusive licence for their project. As with the traditional non-rights protected equivalent, they would also pay every time they used the stock photo. Rights protection is offered only offered for your stock photo purchase when the phrase 'Rights Protection' appears above the calculator.

Screen Ruling

This refers to the number of lines or dots per inch in both directions on a contact screen used to make halftones or separations. Screen rulings are available from 65 lines per inch to 200 lines per inch. For colour separations, however, it is best to use 150 line screens to get the best visual output.

Special

This is a specific colour designated to be printed with a specific matching ink, rather than through process CMYK printing.

TIFF

This is the most common and compatible form of digital stock photo format, this format is uncompressed but gives the highest quality output. Alamy asks for RGB TIFF files from contributors.

Traditionally licensed images

Traditionally licensed images, which are presented on our system by the letter L can be either non-exclusive or exclusive and means that the image is licensed for a specific use. For a non exclusive stock photo, the buyer pays a licence fee each time they use the image, but another buyer can also purchase and use the image under the same license. The buyer must also specify, each time: intended use, media, territory and duration, and pricing is based on this criteria.

Exclusive options for your licensed stock photo purchase are available only where the phrase 'Rights protected?' appears underneath the price calculator. Please see Rights Protected images for more information.

Royalty-free images

Pricing is based solely on the size of output and resolution required, not the specific image use. Once you purchase a royalty-free image, you may use it multiple times for multiple projects though for each project you should check to see whether a Model or Property Release is required for that usage. Note; Not all of Alamy's RF images are model or property released. Royalty-free images are designated by an (RF) next to the identification number.

Saturation

This refers to the density of a colour

Upsize

Refers to an increase in the resolution of a stock photo. Also see interpolation

URL

This is the address of a computer or a document on the Internet that consists of a communications protocol followed by a colon and two slashes (e.g. http://), the identifier of a computer (e.g. www.m-w.com) and usually a path through a directory to a file.

Wet proof

This is a colour proof made from the separations supplied. The wet proof represents the definitive printed colours and is used by the printer as a colour match.

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