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Colour Space

PHD 14 116 United Kingdom
2 Mar 2003 4:56PM
Can someone please tell me exactly what is Colour Space?

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tva 14 307
2 Mar 2003 8:14PM
This is a huge and complex area. Colour space,device calibration and colour management all go together. To answer your question, we humans see a very large range of colours, wavelengths of light. A particular range of colours is called a colour gamut. The gamut for the human eye is described in a colour space called LAB colour(from scientific experiments done in the 30's by an organisation called CIE). Using this colour space you can use all the colours the eye can see. Unfortunately cameras,scanners,printers and monitors all "see" different gamuts, hence the need for calibration and profiling. Photoshop allows you to work in different colour spaces, hence the colour management part.
There are whole forests cut down to write about colour management. So from now on you are on your own. I shall retire before my fingers are worn to the bone. See other posts for colour management issues. Some sites of interest are www.creativepro/author/home/40.html for bruce frasers musings on the subject, also try www.digitaldog.com and Ian Lyons site www.computer-darkroom.co.uk for management.
I'm off for a drink
P.S. If in doubt stick to Adobe(1998) for your colour space, its the widest, giving you the most colours. You can of course make your own if you so wish.
durlstonp 14 638 1 United Kingdom
2 Mar 2003 8:31PM
Short answer: the range of colours that you can use. Home users needn't get overly worried. Just choose one to use for your whole workflow and stick with it. Use either the range of the capture device or the required output.

Longer answer: a bloody complicated nightmare at times! Imagine all the possible colours layed out in a square. You digital capture device cannot capture all of them - imagine its range as a smaller square that fits somewhere inside. Your computer may have another square range and the printer another etc. When swapping from one to another, any colours outside the new range are substituted on a closest match basis, thereby reducing the range of colours in your image. Change several times and your image is limited to just those colours that were in the central arae where all the squares overlapped. It is best, therefore, to stick with the same colour space through your whole work flow. Each colour space has its advantages and disadvantages, but, frankly, you really have to delve fairly deeply to decide which one suits you best. See what the colour space you capture in and stick with it so that you use everything you caught in the first place. If you have a final use that dictates a specific colour space, use that instead. If you are starting in one colour space and MUST produce a different output, change as late in the stream as possible (also save a copy before the change, that way, if asked for yet another change or output in another colour space, you are restricting the full copy and not an already degraded image). If you are a home user, the impact of all this is minimal (just stick to Adobe RGB 98 - the widest range), but it makes a noticeable difference for commercial printing.

PHD 14 116 United Kingdom
3 Mar 2003 5:18PM
Thanks for that. I use Bruce RGB, fed in all the values but didn't understand what I was doing.Seems to work ok!
tva 14 307
7 Mar 2003 7:30PM
Hi phil. what you typed in were the chromacity values. You have probably seen an HSL diagram in some form or another, which shows a cube of the colour spectrum. You can also see it if you look at an image in photoshop in LAB mode, where L is the luminance and a*,b* channels hold the chromacity values. Basically it will adjust the output of your RGB electron guns to give you the depth of hue and saturation required by the bruceRGB colour space.
If you are interested there is a neat monitor test utility at www.entechtaiwan.com called DDCtest which will tell you all about your monitor and what its doing. It will do most makes and is a freebie.
ella 14 43
10 Mar 2003 12:04AM
I am pretty new to photoshop, but not to computers, so I bought "photoshop for dummies". This book has all the basics including colour spaces. I would recommend a copy just to help one get around the whole thing to figure out how much one still has to learn!
PHD 14 116 United Kingdom
10 Mar 2003 8:19AM
Thank you all for replying. Quite a complex subject, but now I have some understanding of what it is about.
PHD 14 116 United Kingdom
13 Mar 2003 4:44PM
One further question. What is the 'Source Space' is this the colour space you have set up in Photoshop under Colour Settings?
durlstonp 14 638 1 United Kingdom
13 Mar 2003 8:07PM
The colour space that the initial shot is recorded in. If you shoot on film and then scan it, it's whatever colour space you scan in (which you can probably change). If you capture digitally, it's either fixed (most digital compacts) or user-selectable (most digital SLRs). Either way, it's whatever you captured in. Check the manual of your camera/scanner.

PHD 14 116 United Kingdom
16 Mar 2003 6:55PM
Hi TVA, I downloaded the DDC Test and it ran ok. The RGB xy values that it gave me, for my monitor, do I now type these in the Colour Settings (Bruce RGB) or do I use them for the Phosphor Values in Adobe Gamma, or do I use them for both?
tva 14 307
17 Mar 2003 9:50PM
Hi Phil - in reply to your question,don't bother if you are satisfied with your monitor as it is set up now. All monitors drift in performance over time, so rerun that utility say every 3- 6 months and then redo Adobe Gamma. Put in the values you get in "phosphers" and "set hardware white point". Thats all there is to it. Your BruceRGB colour space should stay the same.
Hope this helps
PHD 14 116 United Kingdom
18 Mar 2003 9:23AM
Thanks TVA, that's what I did. I wasn't sure if the utility actually measured the Phosphors or whether it was looking at some stored values that the manufacturer had included at time of manufacture.

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