Colour Work Space

Introduction

FIGURE 1 Colour Space settings did exist back in Photohop 5, shown here, but this is a system that is no longer used.

FIGURE 2 It is Photoshop 6, shown here, that introduced the Colour Space settings that are now currently used.

Photoshop 6 should be considered the oldest version of Photoshop that can be used for this training course.  However, there are some other functions, that will be used further on in the course that will require Photoshop 8 (CS1) or later.

FIGURE 3 The Colour Space settings in Photoshop 10, now referred to as Photoshop CS3, shown here, still has the same basic look and options as did Photoshop 6.

So what is 'colour space'?

You will often hear of images being described as having a 'wide' or 'narrow' colour space. To help explain this, think of a common view you may see on a daily basis, the view outside your home for example. Compare the view on a bright sunny day with that on a dull cloudy day. On both days the view is the same; the buildings, road, trees, etc are still there, but the colours that you see them in will be different.

The sunny day will have brighter, more vivid colours than those seen on the cloudy day. Compared to all the possible colours that the human eye can see, the colours seen on the sunny day cover a larger range of the colour spectrum than those colours seen on the cloudy day. In that sense, the colours seen on a sunny day can be said to have a 'wider' colour space than the 'narrower' colour space of the cloudy day.

NOTE:  If you live in Britain you may have to be patient when trying to view the difference as sunny days are quite a rare event!

'Input' colour space

Your digital camera, just like film, has a natural limit to the range of tones that can be recorded. The aim is to try and fit the tones that exist in the scene you are photographing to within the range of tones that the digital camera or film can record. If the scene has too wide a colour space, where the colours are very bright and vivid, then you run the risk of over-exposing the highlights and under-exposing the shadows. Depending on what sort of photography you are doing, then, there various ways of coping with this problem; such as using 'fill flash', light reflectors, or multiple exposures.

NOTE:  These exposure skills are not covered in this imaging course.

The 'Input Colour Space' is only of interest to the photographer. It is the next stage, once the image has been digitised, that the colour space becomes important for those further down the image production line. Of course, the person buying your photographs will want to know if the colours are meant to be bright or dull, but they will not be viewing the scene as you photographed it; they will be viewing the digital file instead.

NOTE:  Digital cameras have internal settings for selecting 'Adobe RGB' or 'sRGB' as the camera colour space.  This is only of importance if you are shooting JPEG files.  If you are shooting Camera Raw files then this setting is of no importance as the camera colour space is only asked for, and a colour profile is 'assigned', when the Camera Raw files are converted.

'Working' colour space

It is the range of colours that you worked with in Photoshop that count.  This is known as the 'Working Colour Space' and must be made public so that the images can be viewed correctly by those using your images, and then be converted to the correct 'Output Colour Space' if needed.

In digital photography there are a set range of standard colour spaces that are common in the industry. From the photographer's point of view the list of 'Working Colour space' can be broken down to three main standards:

'sRGB'  This was created to describe a typical computer monitor, and so is used by web deigners.  It is a narrow colour space and should not be used as your Working Colour space if you intend to sell your images for printing. 

'Adobe RGB (1998)'  This has become the standard within the industry for supplying quality images. This is a much wider colour space than 'sRGB' that not only covers most colours you will photograph, but will also cover almost all possible printing colours used in commercial print presses. For this training course on digital imaging make 'Adobe RGB' your Working Colour space (see the last section on this page).

'ProPhoto RGB'  This was created to cover all the possible colours that can be recorded onto film. This is a very wide colour space and can be dangerous to use if you do not know how to handle it as a small correction in Photoshop can result in a large shift of colours. It is useful when working with very saturated colours, flower photography for example. However, this colour space does also cover colours that are bejond what the human eye can see.  'ProPhoto RGB' is really for advanced users and so will not be covered in this digital imaging course.

There are many other colour spaces available, and you can even create your own customied versions such as a colour space to correct for errors in a digital camera. But this too is not covered in this digital imaging course.

'Delivery' Colour Space

Broadly speaking there are two groups of colour spaces: Private and Public. Private colour spaces are those that you may have created to correct for your digital camera, your computer screen, or your inkjet printer. These are 'your' colour spaces and as such are private, so they should NOT be passed onto others as they will not be using your equipment. Which ever 'Working Colour space' you end up using it is important that you 'convert' this to a Public colour space that everyone else can understand.

For simplicity at this stage, set your 'Working' and 'Delivery' colour spaces the same 'Adobe RGB', as this will save you doing an extra colour conversion. For most photographers this is all you will ever need to do, and you will not need to change unless you start to do more advanced colour correction.

Usually clients will ask that images be supplied in the 'Adobe RGB' colour space, but sometimes the picture library or publisher may request something different.

RULE #1:  As a general rule, supply the clients with what they want and the way they want it, after all they are the ones with the money.  Check with them first as picture libraries usually publish what their submission standards are. If there are no set colour standards then 'Adobe RGB' is the safest colour space to supply, but do tell them what you are supplying.

RULE #2:  If there is no agreement about the colour space then you do run the risk that they will say later that the colour is wrong, thus giving them the excuse not to pay you. If there is a dispute about money then usually the person with the cheque book wins; and that is very rarely the photographer.

'Output' colour space

The 'Output Colour space' is that used by the medium that your images will be reproduced in, such as a website, projection slides, inkjet printer, a quality magazine, or a daily newspaper. All will have different colour spaces due to the limits of the various technologies involved. As an example, below is an image reproduced from the same original RGB digital file, reproduced in two different newspapers that have two very different colour spaces.

FIGURE 4 Here we see a low quality newsprint. The result is poor, not becaue a mistake has been made but because the ink and paper used in newspaper production is usually of poor quality. This will vary from country to country and between publications, but the cheaper the paper, the worse the print quality. The highlights could have been better in this reproduction, but nothing was going to save the collapse of colour here.

FIGURE 5 Here is the same image, also reproduced in a newspaper, but this time with a much better quality paper. It is still being produced on newsprint so the image will not look a good as it would have in a quality magazine.

Usually the photographer is not involved with the 'Output Colour space'.  If you are supplying a picture library then your images may have many different uses. Even if you are supplying a print publisher, they are likely to have more than one use for the images besides printing, such as a website. Normally it is the job of the photographer to supply the images at the highest possible standard to cover all possible uses. It is the job of others, such as designers and website managers, to convert the images for each particular use as they are the ones who will know what the colour limits are. Or they should know, but in practice they often do not.

RULE #3:  If you are asked to convert images to print colours (CMYK instead of RGB) then the simple rule is do not do it.  If you do know about the required CMYK colour space, and are happy to do the work then, like all work, make sure you get paid for it. The problem is not in the colour conversion, as it is not difficult to learn, the problem is that by converting images to the printer colour space you are then taking the responsibilty for any errors that may occur. So unless you are prepared to not be paid if things go wrong, and some designers are very happy to let the photographer take the blame for this, then the rule again is do not do it.

RULE #4:  If you are converting images for use on a webite or in projection presentations such as PowerPoint, then convert the colour space to 'sRGB'.  Most webites and presentations do not not understand colour space. The day will come when they do, but in the meantime the 'sRGB' colour space will fit in reasonably well with most monitors and projectors that the images will be viewed on.

What settings to use

Open the 'Colour Settings' in Photshop.  At first all the available options may look a little daunting, but do not worry as there is only one thing that needs to be changed here.

FIGURE 6  Here we see just the top of the Colour Settings panel and the part that is going to be changed is the 'Settings' option at the very top.

Photoshop is an American product that is used within the graphics industry, so usually the default setting is listed as 'US General Purpose'.  This will have set the 'Working Spaces' below to 'sRGB' for RGB which we need to change.

Rather than set each of the 'Working Spaces' though, open the 'Settings' drop-down list and look for the word 'Prepress'.  The world is divided into three broad geographic areas as far as printing is concerned, so select one of the following that fits in with where you are working:

Europe Prepress 2

Japan Prepress 2

North America Prepress 2

Older Photoshop versions may have '...Prepress Defaults' instead of '...Prepress 2', but the clue is to find the word 'Prepress'. All the prepress options will set RGB to 'Adobe RGB', but they will set different values for the CMYK and the Grey. While you may not become involved with converting images to the printing CMYK color space you will need to check your image colours against the local CMYK settings at some stage to make sure that you are not passing on any colour problems to those who will be doing the conversion work. This issue will be dealt with later on in the digital imaging course.

If you do not see your local area listed, then click the button near the top right called 'More Options'. Now look back in the 'Settings' drop-down list and you should see all the available options.

If you are unsure as to which geographic area your country comes under, from a printing point of view, then seek advice from a designer or a printer operator.

NOTE:  The European standards for CMYK have been going through a series of changes over the last few years, from 'Euroscale Coated' to a 'FOGRA' standards system which newer versions of Photoshop will have listed.  If you agree to convert images to the printing CMYK colours and your clients have asked for a FOGRA setting such as '27' or '39', then do check that your verion of Photoshop does have these options installed.  The FOGRA standards are small files that are freely available from the internet, but again, unless you know what you are doing then the RULE #3 above needs to be repeated: do not do it.

'Assign' and 'convert' colour space

There is a major difference between 'Assigning' and 'Converting' image colour spaces.

FIGURE 7  Here we see the dialogue box that allows us to assign a profile. 

When an image is digitised it has a colour space that it inherits from the equipment that created it, the camera or the scanner.  What the image needs next is a label that describes what the colour space is. This is refered to as 'assigning' a colour Profile. This Profile does not change the image; it is just a label that describes what the colour space that is contained within the image. 

There is an alternative option here. A different colour profile could be 'assigned' that corrects for the errors that came with the digital camera or the scanner equipment. This would require having the required equipment to create the camera or scanner profile, and is something best left to a more advanced digital course.

FIGURE 8  Here we see the conversion dialogue box options.

Once the correct colour space has been identified, and the colour profile has been 'assigned', then the colour space has to be 'converted' to your 'Working Colour space'.  However, we need to keep things simple at this stage by just 'assigning' the 'Adobe RGB' colour Profile so that no conversion is needed. Any camera or scanner colour errors can be corrected with Photoshop, although it will later improve productivity if these correction colour profiles were available.

When the image is saved, do make sure to tick the option in the 'Save As' panel to embed the colour profile. This will allow others down the production line to see what the image colour space is.

Quick summary

1. When photographing, you will often be dealing with very wide colour spaces, especially outdoors on a sunny day.  You will need to use photographic skills to reduce this wider colour space to fit within the limit of the digital camera or film.

2.  Once the image has been digitised, either shot on a digital camera or scanned from film, then a colour profile needs to be 'assigned' to describe the colour space that the image contains. To help simplify things at this stage, start with 'assigning' the 'Adobe RGB' colour profile as the colour space.

3.  Set up your 'Working Colour space' in Photoshop to 'Adobe RGB'.  There may be reasons to change this later at a more advanced level of colour correction.

4.  From now on, once the images have been 'assigned' the profile to describe the initial colour space, they should only be 'converted' if the colour space is to be changed.

5.  Deliver your images to the client in the 'Adobe RGB' colour space, unless specifically told otherwise, and make sure that the images are saved with the colour profile embedded.

6.  Do not get involved in the conversion of images to 'output' colour space, especially printing, unless you are prepared to take the responsibility for any printing errors, and that you are being paid for doing so.