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I took a picture of an oil painting. I have two softboxes at about 45 degrees. On the picture I get tiny bright white spots, caused by relief in the paint. I tried changing the position of the lights, but that removes some reflections and gives me other reflections in return. I tried removing the spots with gimp, but I couldn't get it right.

In another question I read that a polarization filter helps. I'll try that. Is there anything else I can do?

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An elaborate copy setup would have rotatable polarizing gel filters on both lamps as well as a circular polarizing filter mounted on the camera lens. Before you take any of these steps, suspend a white bed sheet in front of the painting. Cut a peep hole for the camera; illuminate the painting thru the bed sheet. The idea is totally diffused light.

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  • \$\begingroup\$ I ordered a polarizing filter, I'll see what I can do with that. Reflections are polarized by themselves. \$\endgroup\$
    – Christine
    Commented Jan 10, 2018 at 22:54
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    \$\begingroup\$ @ Chistine --- Light travels much like water waves. Water waves ungulate up and down. Light undulations are not so restricted, they ungulate up down, left right, diagonally, in all possible planes. Upon reflection or transmission, some materials alter the undulating direction, often it becomes restricted to one plane. The polarizing filter only allows rays undulating in one plane to pass into the camera. We mount the filter and then rotate it for best effect to mitigate reflections. Polarization means the direction of undulation was changed. This will be your most valuable optical filter. \$\endgroup\$
    – Alan Marcus
    Commented Jan 11, 2018 at 2:13
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    \$\begingroup\$ @Christine --- As Allan said you need the polarizing filter on your lens but you also MUST have polarizing gel filters on your light source. Both gel filters need to be oriented in the same and proper direction. Because the strokes of paint on the canvas are in many different angles this is the only way to eliminate any and ALL reflections. \$\endgroup\$
    – Alaska Man
    Commented Jan 11, 2018 at 3:45
  • \$\begingroup\$ Do not forget to turn off all other lights in the room, they are not polarized so they will cause reflections. You can read my answer to a similar question here. ( essentially the same as Allan's ) photo.stackexchange.com/questions/6625/… \$\endgroup\$
    – Alaska Man
    Commented Jan 11, 2018 at 4:15
  • \$\begingroup\$ @Christine -- What Alaska man said is spot on but --- a polarizing filter on the camera and none on the lights might do this deed. \$\endgroup\$
    – Alan Marcus
    Commented Jan 11, 2018 at 4:16
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It sounds like you want to avoid directional lighting, and utilize more ambient light. If you have control over lighting in the room, you could skip using the soft boxes and just increase the ambient. Otherwise, you could try bouncing the soft boxes off walls/ceilings (i.e. not pointed at the painting) to increase their apparent size, which will approximate an increase in ambient light. Using larger soft boxes or reflectors might help as well.

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One thing you could try is taking several pictures with the lights in different arrangements, then stacking the images in Photoshop and setting the layer blending modes to Darken. All the white reflection spots will be lighter than the same patches on differently lit shots, so won't show up. I haven't used Gimp but it may have the same functionality.

Edit: If you can't avoid slight differences in position for each shot, then in Photoshop you can do File > Scripts > Load files into stack... and tick "Automatically align images". If you can't do that then you can try setting the opacity of the layer to around 50% and nudging it with the arrow keys until it lines up with one other layer, then repeat for the other layers.

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  • \$\begingroup\$ I guess you need a very heavy and stable tripod for that. Not sure mine is good enough. \$\endgroup\$
    – Christine
    Commented Jan 10, 2018 at 22:54
  • \$\begingroup\$ @Christine Most tripods should do fine. If you can't avoid offsets for each shot, in Photoshop you can do File > Scripts > Load files into stack... and tick "Automatically align images". If you can't do that then you can try setting the opacity of the layer to around 50% and nudging it with the arrow keys until it lines up with one other layer, then repeat for the other layers \$\endgroup\$
    – binaryfunt
    Commented Jan 10, 2018 at 22:59

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