Retouching glare in oil-paintings

Software RawTherapee
1

Dear all, I frequently visit musea where I photograph paintings, sometimes these are available through their websites, sometimes only in low resolution. Besides having a challenge to arrive at the correct color depiction (not my question of today blush: ) frequently light reflecting from oil-paint is causing multiple spots of overexposure. In this case (tower of babel: Pieter Bruegel) on the Top Right. My question: what approach would you recommend to remove these annoying spots … Thank you for advice.

DSC07574
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DSC07574.JPG.out.pp3 (14.1 KB)

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with spot removal tool, this would be a hard job, so better try the local adjustments:

my first approach would be log encoding: put a spot with small size, onto a white reflection, reduce the scope and give it a try

grafik
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may be, similar results can be found with color and light

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I thought of layers and masking but in the GIMP:

mask

mask
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tower+mask+reduced exposure

babel+mask
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But the mask was hard to make and not all that good so, like @marter, I selected the area, then applied 9.5 px Gaussian blur.

Blurred

blurred
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Of the two I would prefer to spend more time on a better mask but RT doesn’t do masking.

As to blurring, specular reflections don’t always fall into an easily-selectable area like the above.

Actually “removing” multiple small specular reflections is a hard task indeed…

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Hello, removing reflections from a photo of an oil painting is nothing less than hell (been there, done that). So avoid reflections in the first place and use a circular polarizer filter when shooting.

The following article explains how such a filter works, see point 1 and 2.

1 Like
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I agree with @paulmatth that you want to avoid reflections in the first place. Polarizing filters are a huge help. Another method I use is to shoot the paintings off centre by moving to the side until I see no reflections. I then use darktable’s rotate and perspective module to square the image up again as if I had stood in front of it. I am sure RT has similar tools to achieve this.

This shooting from an angle is also important if you are using a flash because if you stand directly in front with the flash on the camera then you will get glare and even a polarizing filter will not help in that case.

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Thx @marter ! Nice proposal, will definitely try :slight_smile:
Hi @cedric , not ideal, but I get the idea, not bad at all, yet depends a lot on the quality of the mask, right?
@paulmatth , indeed, not easy. I definitely would consider a circular polarizer, although most paintings are displayed in low light conditions … … forcing me to go to high ISO numbers, the filter will make that a lot worse, but with lots of light, definitely a good option (avoiding these problems in the first place).
@Terry, RT indeed has a perspective module, probably similar to Darktable. Use of flash normally is a no go (degrades paint colors more rapidly). Thx for suggestions though :slight_smile:

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Yes, I may have mentioned that …

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I move from side to side when photographing a painting until I find the position with least reflections. Often works, but with glass it sometimes becomes impossible to find a perfect angle. Polarizers cut down the light as you say and I often don’t have one on me anyway.