photoshop query colour management

[galanthus]

I occasionally get a box with error message re embedded colour profile not matching RGB ? It then gives me choice of :-

use embedded profile
covert doc colours to working space
discard embedded profile don't colour manage

which is best to choose ? I print quite a few out and also put some on my web page.

I've now chosen the adobe RGB option on my canon 400d, instead of sRGB, was this the right thing to do ?

my final docs never seem to match my monitor anyway despite attempting to change some settings as advised in a photoshop book

help pls ?

[zharca]

Hi,
I would only choose Adobe RGB as the colourspace for files in the publishing environment. It's really optimised for working in CMYK where the ink densities are set for printing presses, so the results can look a little "flat" on screen or on the web because you'll lose some density range in the shadows.

Even if you want to deliver CMYK, I think it's probably better to have the camera deliver the sRGB colouspace, which is the "natural" choice for RGB mode, and rebalance in Photoshop when you change modes. If you don't want to remove the profile on opening, just tick the "ignore exif profile tag" in the file handling preferences, otherwise set Photoshop to discard the profile.

In reality unless you are running a complete calibrated system from camera through monitor to output device, including RIPs and printing presses, I think embedded profiles are simply a nuisance. You can set Photoshop to save without profiles. For our work image library we always remove them because they can cause problems when making output PDFs and stuff. They will go anyway when you save for web.

[zharca]

Sorry, forgot the monitor matching bit!

For making the printer output match the screen, unless you can get into serious calibration stuff, the best way is to work backwards! Make yourself a test page in Photoshop using solid colours of known values, like 100, 50, 25% of C,M,Y and K, and a greyscale step wedge, print it out and then match the screen to the result. You can then fine-tune it by printing some test pictures, adjusting the screen to the print-out.

This way, what you see on screen is what you will get as a print.

[eeyore]

although monitor calibration itself isnt that big a deal - you basically get a "spider" which sticks on your screen and some software runs colour charts for it to read and adjusts your monitor settings accordingly

i have a very expensive gretag macbeth one - but eyeone do monitor calibrating kits which start at £49 notes and do a good enough job for most enthusiast applications.

[galanthus]

phew, complicated stuff Will attempt some of these things tomoz, thanx both very much.

[zharca]

But calibrating a display in isolation is a waste of time, unless it's part of a complete colour management system chain from source to press, including pdf creation, rip, platesetter, paper stock and ink brands. Your display also needs to be calibrated to agree with every other one down the line. That's when working to an agreed colour profile starts to make sense.

For serious on-screen proofing the display has to be in a controlled environment - balanced lighting, no windows, individual user settings, even mid-grey overalls to avoid casts. Even then, it's still subjective because you're viewing additive RGB against a subtractive CMYK output.

That might sound a bit tetchy but, in an my work environment with dozens of picture and art desks, we've had many expensive tries at colour calibration for over a decade and the conclusion is that the monitor is no substitute for being able to read the values in the info pallette and to understand what they mean for reproduction.

If your finished product will always be your home printer, just set the display look how the ouput result appears to your eyes in your room.

[eeyore]

i have no doubt that you are correct about the proffesional level work - much of my work goes to magazines and i know that picture desks regularly have to rebalance pictures even where the photographer has done their light room work on a calibrated monitor.

However for the purposes of printing your own pictures ( I regularly print mine to A2+ for sale as prints) i would say that it is virtually impossible to accurately set the colour values on your monitor based on a visual appraisal of a print - the approach which I find works better for me is to colour profile the monitor with a GTMB spider then download printer profiles to match - taking into account the various media i am printing on.

at the end of the day both methods are valid and which is chosen will come down to individual prefferences

[zharca]

Eeyore, you’re right that a properly set up source-through-output workflow is the way to go for a professional environment when, once the setup’s done, time saved equals profits but, as I said at the beginning, getting into serious calibration and profile stuff might not really suit the average home computer setup.

I think that to get the best possible prints from your files in a home environment it’s still worth considering working (or at least thinking) in CMYK mode, because that’s how your inkjet or laser printer will output. After all, that conversion will be done on the fly when you press “print” and it’s maybe better to be able to assess the result first.

When you change modes, some colours are going to alter simply because you’re going from light-based to ink-based ones. With a bit of practice, you can learn to assess how the file will output and adjust it for best printing. What looks great on-screen doesn’t necessarily work well transferred to paper. For example, if the info for a shadow area is reading 90% for each channel then the print is likely to fill in all shadow detail. At the other end of the scale, most sensibly priced printers won’t print highlights accurately once the values get down to around 5%. If you feed the printer a file that keeps within its limits, you get the best prints.

[Tormentil]

So, if I'm using sRGB for my monitor, should I alter my printers colour profile to the same ? Printer is a Canon i990.

[zharca]

Hi, One of the best things you can do is to match the profiles across the whole process, then all the stages are agreeing and the various stages won't make changes to the appearence each time. Try setting the printer to the same profile to see what you get, but this might not give the best result as it means the printer software will be performing the output remapping and you might get a better result by allowing Photoshop to do it. In that case, in Photoshop colour settings, starting with the "Europe general purpose" try setting RGB to sRGB and the others to your printer's output profile for the paper you're using.

What the profiles do is to describe how that device handles colour - it's really just a big table of numbers. I think the most important part of the chain in a regular camera-computer-inkjet setup is the relationship between your image software and the print engine. This is where the big colourspace remap (rendering intent) happens, so it's where the interpretaion of colours will change most, unless you are already working in CMYK.

In Photoshop, to have a look at how the file will print, rather than how the RGB file looks on screen, try using "view > proof colours" which will match the on-screen image to the output. You can also use "gamut warning". This will highlight any areas where the printer won't be able to match rgb file.