[Digikam-users] A few thoughts about color management

[Remco Viëtor]

On Saturday 01 October 2011 19:17:33 sleepless wrote:
> Hi All,
> 
> A few thoughts about color management to share. Moving from windows to
> Ubuntu brings enough changes to workflow to need a lot of adjustments
> and a heap of dimes for tests prints.
> 
> Why color management is doomed to fail:
[snip...]

To be frank, I think you miss the point of colour management.

Colour management is ment to ensure that for a given input, you know what's 
coming out. In the case of photography, you want to make sure that a photo you 
open will display as close to correct (as defined by the colour space you use) 
as possible, _independent_ of differences between devices.

To take your reasoning point by point:
-- Colour of scene lighting:
by using a neutral gray or white card, we can ensure that we know the light 
temperature, so we can correct for it. Using a colour card allows correction 
of differences caused by the camera/lens.

-- Camera manufacturer applying a correction: 
that only applies to in-camera jpg, if you want to go through the effort of 
colour management, you should be using raw format anyway (imho).

-- Import in computer/screen display: 
To correct for differences in screen/graphics card response, you calibrate and 
profile your screen, so a colour in your photo is displayed as close as 
possible to the intended colour.

-- Printing: same as screen, but (of course) with different correction 
profiles (of course, as it is a different device).

In short, one aim of colour management is to ENABLE you to get as close to the 
original colours as possible...

There is a second point as well, concerning screen and printer 
calibration/profiling: if you use screens as set by the manufacturer, you'll 
have (big) differences between screens (even of the same make/type). By 
calibrating and profiling the screen, you can have some confidence that 
someone else sees the colours you aimed for, especially if that someone else 
also has a calibrated and profiled screen display. When NOT doing any colour 
management at all, don't be surprised that the lovely portrait you prepared is 
seen by someone else with a green cast...

As for the better way you propose:
you can't use the same profile anywhere. You'll have the colour space you work 
in (sRGB usually, other possibilities are Adobe RGB, ProPhote RGB, etc.), and 
correction profiles for your camera(s), screen and printer. And please don't 
mix up the colour space definitions with the correction profiles (although 
they both use .icc or .icm extensions, they are completely different beasts).

Having a room with controlled lighting is indeed the ideal situation.

As for composing a test print and adjusting it to get the best possible print: 
how do you define 'the best possible print' in an objective way? And how many 
phtographers do print at home. I don't, given the investment required... 

I do make sure my screen is calibrated and profiled though. That at least 
allows me to prepare my photos and look at those of others with a reasonable 
confidence that I see the colours as intended (*note*: not necessarily 'as 
they were in the scene'!).

And as a final note: colour management is there:
1 - to enable you to get the original colours as they should be under neutral 
light, *when you need that*.
2 - to make sure others see what you intented them to see (supposing they also 
use colour managed equipment).

Starting from there, you have a known basis, and you can adjust the colours as 
you like, knowing that others can see the same thing you do.

Sorry if this got a bit long (I still restrained myself...), but I often see 
misconceptions about colour profiles, calibration and profiling (not 
necessarily here). You might want to have a look at
http://www.cambridgeincolour.com/color-management-printing.htm
for more information.

Remco