Colour Space and Paintings


Lubbyman

Link Posted 25/09/2020 - 09:20
A bit of background before a question...

An old friend and amateur watercolour artist died a while ago. He left hundreds of paintings in drawers and cupboards. His family are keeping them but, realistically, they are likely to stay packed up in a cupboard once they have been put away. I am therefore photographing at least some of the paintings so the family can see and appreciate the pictures at their convenience on their computers/tablets/phones/whatever.

As a matter of policy, I am trying to be as faithful to the originals as reasonably possible (so no tweaks to make the images look 'better'!). And that raises the issue of colour space. I am using sRGB for two good reasons, first because that's what the recipients will have on their monitors, second because my own monitor is sRGB (99.99% and calibrated). However, an artist is not restricted to sRGB and I wouldn't be surprised if some of the colours in some of the paintings are out of gamut (subtle greens in landscapes etc.). Colour matching is so far pretty good (visual comparison between painting and what's on the monitor). But there are lots of paintings to go (about 600 if I go the full distance!).

So now to the question. How can I tell whether colours that are not quite matched are out of sRGB gamut, so cannot be matched by tweaking, or within gamut, so could in principle be tweaked to match? I am well aware of websites that show sRGB triangles and other colour spaces on a notional 'full scope' colour gamut, but that's no use because all the colours display on the monitor as sRGB. If it's relevant, the starting point for post-processing is a DNG file from a K3, Affinity Photo is used for processing, processed image saved as both 16-bit TIF for archive and JPG for normal viewing

Hopefully, there won't be a painting where non-sRGB colours are a significant problem, but you never know...

Steve

johnriley

Link Posted 25/09/2020 - 12:17
Whatever you do viewing a painting is very different to viewing a painting via a camera and a monitor. It's a fair question that you are asking, but I do feel that you could tie yourself in knots trying to achieve something that is beyond what we could reasonably expect to achieve.

I would suggest the family display the paintings in their various homes, not all of them, but a few selected ones, that can be rotated so they all get a viewing sometime. Then you could produce a record shot of each, shot using good daylight and the daylight setting on your camera. JPEG capture should be fine for this, and the result will be very close. Don't use AWB as that will try to inegrate the colours to a neutral grey, which could lose the nuances of the paintings.

In summary, accept something very close and don't overthink it?
Best regards, John

RobL

Link Posted 25/09/2020 - 12:58
As John says, donít overthink it. The only thing I would say is framed watercolours will be behind glass so best to take them in the raw as it were, and if they are in mounts then that will keep them fairly flat. Use the longest practicable focal length to minimise distortion and try to get as even a natural light as possible, using a reflector if necessary. Given there are so many paintings would it be best if you and the relatives pick out their favourites to tackle first?
Last Edited by RobL on 25/09/2020 - 13:01

pschlute

Link Posted 25/09/2020 - 13:38
Lubbyman wrote:

So now to the question. How can I tell whether colours that are not quite matched are out of sRGB gamut, so cannot be matched by tweaking, or within gamut, so could in principle be tweaked to match?

I agree with John and Rob. Especially with 600 paintings to work on !

However one thing you can do if you find an awkward mismatch is to do a proof gamut warning. I only know Photoshop, not your software I am afraid.

In Photoshop I would process the raw file in a wide colour space like AdobeRGB or ProPhoto. Then open the image. Using the soft proofing tools select the "device to simulate" as sRGB. If there is an option to "preserve RGB numbers" make sure it is unchecked. Then select "Gamut warning". Any colours that are not capable of being displayed in sRGB will be highlighted.

The problem here however is that unless you have a wide gamut monitor to view the image on while working on it, you wont know if the wider colour space image renders the picture any more accurately than in sRGB ! If you have a significant mismatch you will be just as well to try and eyeball the colour to the closest match rather than delve into the dark arts of wide gamut editing.

One final thing is that although you profile your monitor to get accurate sRGB display colours, I doubt your family do, so what they will end up seeing is anyone's guess
Peter



My Flickr page

Lubbyman

Link Posted 26/09/2020 - 16:46
Thanks for the advice/comments folks.

I'll come clean here and admit that my question is a bit of perfectionism on my part, not a real need to produce colour-perfect images. It's something I've wondered about for some time and thought that now is perhaps the time to try to get an answer on the back of wanting to do a good job on the life's work of an old and talented friend . The family are definitely not wanting perfect images, I offered to produce them and they are just grateful for whatever they get.

Peter - your suggestion of working in Adobe RGB and soft proofing to simulate sRGB is interesting. I'll see what Affinity Photo can do (I currently have no idea what most of the options, buttons and sliders do!).

John, Rob - Normally, I would agree with taking photos of paintings in the environment in which they will hang so lighting etc. is correct. But in this case, the paintings are not mounted and will not be hanging anywhere. The family actually run an art/craft shop, 3rd generation (the deceased was 2nd generation), and already have more than enough art hanging on their domestic walls (trade price etc.!). The paintings will be kept in a cupboard in the shop for safekeeping and as 'family history'. Digitising the paintings means that they will be able to see them at home whenever they want to. And if anyone ever wants to make a full size print of any of the paintings, the TIFFs should be adequate.

Rob - Natural light - yes, always. Reflector - didn't think of that for the first batch, but what I thought was uniform illumination turned out to be not quite so thanks for the suggestion for the second batch! Lens is F 50mm f1.7 @ f5.6 (on K3), not enough space for anything longer, but I've used it for a painting or two in the past and it seems to do a good job. Once everything is set up and checked out, it's quick and easy to change the picture, check alignment through viewfinder, fire shutter from remote, repeat ad nauseam. Average about 2 mins per picture. As for post-processing, again a couple of minutes per picture unless something odd has happened, but with the right music playing the time passes quite quickly .

600 pictures sounds (and is!) a lot, but I'm looking at this as a project for the colder, wetter days ahead when the lure of the great outdoors isn't so strong!

Steve

RobL

Link Posted 26/09/2020 - 17:31
Lubbyman, if the light isnít evenly distributed in the first batch you could try applying a graduated filter to lighten them locally in post processing, a bit of tweaking should get it right.
Last Edited by RobL on 26/09/2020 - 17:32
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