----- From: "lea murphy" :color space questions : First of all, thank you to those who responded to my color management : question a couple weeks ago, especially karl shah-jenner, as your : info was most helpful. glad to hear it :-) :If you don't mind bearing with me, I have at : least a couple more questions before I get going as I should. : Let me come clean. I don't really 'get' color management. I'm not : clear on how all the different 'spaces' and 'profiles' work together : (is a space the same thing as a profile? See, I really don't get it.) : and when to apply one. It's important to understand this stuff now that many are work digitally to some extent. Just as it was important for *some* of us to understand colour processes when we worked with film. Admittedly a lot of processing steps were handled by specialised pros in the field - film chemists, lab staff who really needed to understand all the intricacies of the medium, leaving we photographers to just shoot our film safe knowing the rest would be handled properly. Now days you're on your own, there are no chemists running monitoring processes so the whole colour monitoring and control process is in your hands, and is something each individual must learn. Don't forget that this fact alone was something people yearned for - the ability to control every step themselves without the risk of someone else making a mistake somewhere - now we all get to make our OWN mistakes ;-) Onto colour space or Gamut Colour space / gamut is the limit of colours a device can represent - a monitor can make very deep rich colours with very high contrasts, a printer has a lot less colours and a lot less contrast. Think of it as similar to slides V prints - slides like monitors show you the image by transmitted light and subsequently have a huge contrast (contrast being the difference between black and white) while a print is viewed by reflected light and has a heck of a lot less contrast. you know this from whenever you have a side printed on cibachrome - the richness, the depth of tones is lost - you can only make a print so black and so white.. Each device has it's own colour space or gamut - it's limit to the range and depth of colours it can make. Speaking of monitors for a bit, each monitor will have an upper limit to the amount of colour it can produce - you can't go beyond these colours however there are a number of ways to modify the displayed colours. You can't set the monitor contrast, gamma and colour balance directly from the monitor internal electronics, but these are done at the factory - nonetheless if you imagine for a moment that someone has turned down the green gun in the CRT a bit, then to obtain neutral tones you'd have to adjust the red and blue guns down too (using monitor controls)- effectively lowering your brightness and thus contrast.. and thus your colour range and contrast will be lower than were that green gun turned up. You can however adjust the monitor directly using the colour/contrast/brightness/other settings built into your monitor by twiddling the monitor switches and menus and this can be done independent of the computer. When setting up through adobe gamma for example, the first thing the program asks you to do is "first set the contrast to it's highest level" and gives you a grey/black box to examine while you are doing this.. you use the monitor controls to perform this task. Another way to modify the perceived colours is through the video card - what info this squirts out to the monitor in the form of colour depth. Is the monitor set to 256 colours, 16 bit, 24 bit or 32 bit? (Is there a 48 bit yet?) Each will produce not just the various levels of banding you will or will not see, but obviously also the range of colours. Assuming so far that all are set to maximise the depth of colour and range of contrast, you will have the best colour space possible from this particular monitor :-) but we're not done yet Next we have to make sure those colours render in as *matched* a fashion as possible. Harking back to film again for a clue - if our processing was off or if we excessively pushed or pulled a film we'd find the curves shifted out of alignment and behaved weirdly - the most extreme example of this was cross processing when the red, green and blue layer curves move so wildly away from one another that it's simply not possible to bring them back to true, so the colours will be wrong. We might achieve a neutral grey in the mid tones, but the blue and yellow will be skewed so that highlights will be yellow, and shadows blue. If we get the shadows neutral the rest of the tones shift to yellow, if we get the highlights neutral the darker tones shift blue. nasty. Fortunately when we buy a monitor it's close to right and we don't have a lot to do, but because we are trying to work as close as possible to true we will still need to get these colours *more* right. So we fire up some sort of calibration software or we adjust by eye for the fine tuning and we start to move from the realm of 'colour space' into 'profile'. The software and bits of hardware around for calibrating monitors all perform various functions designed to render colours as correctly as possible, some like the Spyder thing work by using colour analysers work toward colour accuracy based on certain standards (whatever these standards may be - and these are the magic 'profiles') while some others use your personal perception of colour, such as Adobe Gamma. They are not however interchangeable - each profile is designed to function is a certain environment and there's no cure-all that makes everything work all of the time! Each profile will chance the gamut of your monitor, shrinking the colour space to a certain degree. Leaving this part of monitors aside for a while, we'll consider the monitor profile and how it ties to output. Ultimately you will have different intents for each image, and different profiles will need to be applied for each final step. An example I used before was the CMYK approach. Most print presses have 4 colour inks and they frequently work with the Pantone colour range (there are others, and many other colour standards but lets work theoretically with one and hope we never have to deal with it, or others like it ;). This standard has been set to allow graphic designers to design stuff up on their computers profiled to this limited colour range so they know when it's sent to print the colours will reproduce VERY closely to the gamut the printers are capable of printing. Their output and workflow is NOT based on perception of colour, but rather colourimetric values. What this means in a simple sense is that the light source by which the final images are viewed is immaterial - the colours may look *quite* wrong to our eye, but under a colour analyser they will match a set of standard colours like a swatch from a pantone chart. They will use a Spyder and set up the computer to the standardized gamut of the 4 colour printer and match their monitors, software and input devices to this standard, the standard being limited to the output device. Thus when they load a colour into a block of text or a background they will see on their monitor what that colour will look like in relation to others once it rolls off the press, and were they to lay the original colour swatch beside the print the two should match precisely. However anyone who's had the pleasure of seeing their work in print will have discovered that many graphic designers have a bit of a problem with photographs. You see there are no standard colours in a photo image, there is nothing they can lay a swatch against to check the colour and to top it off, there's no way a 4 colour printer can reproduce the colours we get out of an RA4 machine or a slide anyway! They will run an eyedropper tool over a photo and guess the colours, then maybe make a slight tweak (or not) before dropping it into their publication. (fight ensues between graphic designer and irate photographer, each accusing one another of not understanding colour!) A case of different intents.. So we need a profile set up for our monitor which matches the gamut of the 4 colour printer which we can load* when we want to do work for magazine printing. (* by 'load' I mean we 'apply' this monitor profile, which will proceed to alter the colours on our monitor to match those that this 4 colour printer can produce - we then need to 'tweak' those colours to make them look acceptable to us and to how we'd like it to reproduce) Of course we also use a mates 6 colour wide format printer, and our own 8 colour printers from time to time too - so we really need profiles for these as well! We should be loading each of these profiles while working our image so the 'profile' (colour modification) shows us the colours on the monitor such that they match the colours our chosen printer can produce. ..and there's the Frontier we send images to from time to time, and they use different paper stocks as well, so yet more profiles are needed. Each image NEEDS to be modified and manipulated within the colour space profile of the intended output device otherwise the colours or contrast will be wrong, so we really do need a fair few profiles tucked away. Of course they need to be backed up too, and we need to be able to check to see if the correct profile is actually loading when we attempt to load it, and then there's the issue of the colour drift in a CRT as it heats up, cools down, starts, wanders with shifts in power etc etc etc.. <groan!> It is a lot less trouble for the graphic designers though, once a profile is set they tend to work pretty exclusively with it and it alone, aside from maybe the proofing they do with a single printer who's gamut will be crippled down to closely match the gamut of the big 4 colour printer. now here's the BIG difference, unlike the graphic designer who's workflow is geared toward a single output device with a limited gamut, we often want to get the BEST colours we can out of a printer to make our images as rich as possible! At present we can get our biggest gamuts, the most colours, in diminishing order from: 1. Film output devices - like the Polaroid propalette 8000 2. Frontier printers and other laser/led devices that image to RA4 3. 8 colour (or better) dye ink printers 4. 6 colour dye ink printers 5. 4 colour dye sub printers 6. 8 colour (or better) pigment printers 7. 4 colour dye ink printers 8. 6 colour pigment printers 9. 4 colour pigment printers Obviously changing inks, manufacturers etc will change our colours, as will to a lesser extent changing the media on which we print. Oh yeah, the varying papers will all need different profiles too :-/ So rounding up, we build ourselves all the profiles (colour modifiers if you like) that we need, and we apply each one as needed to our monitors to allow us to see the colours that our printer can produce. It's actually a lot more complicated than this and the steps folks take to get their profiles can be many and varied, some quite expensive - most are time consuming, all are frustrating and the results are often wrong :-( Colour management is a massive headache to everyone who delves into the subject and it's applications, and as I said before every year some company or consortium invests millions coming up with new standards that will hopefully simplify things and next year the process gets repeated all over again. The best I can suggest is to latch onto something, ANYTHING that gets you close to what you want then 'tweak' until you get closer. Lastly, if you're working toward web images use the broadest gamut you can - adobe rgb or, NO profile and work with your histogram tool to make sure you have your tones distributed as appropriately as possible. Most browsers ignore profiles anyway so if you've attached something it will just be ignored and the simple RGB values will be displayed to the viewer - who invariably has a cheap, 10 year old monitor.. out of alignment, with moiré issues.. and a collapsed red gun set to 256 colours :-P : I know my lab's Noritsu is set to print in sRGB (as are almost all : lab printers if I'm not mistaken). In PS should I be converting to sRGB? yes :) : Also, I have downloaded my lab's printer profile and can set that as : my color space in PS. Should I be doing that? it's a good start! : I am so confused. we all are! : Any suggestions? fiddle, tweak and muddle until you get closer to what looks good to you :) k
