Photographing paintings behind glass

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justinhession

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I have to do some photos of some paintings for a catalogue that has to be reproduced exactly. Some of the paintings are behind glass that can not be removed. I realise there will be reflection problems. Can any give me some suggestions as to how to stop the reflections. I will be using stobes as the lighting source and shooting in a studio. Any help is much appreciated
Thanks
Justin
 
Moved to the correct forum for you :)

Plain reflections would be partly removed by a polarising filter wouldn't they?
I'd say alot of it comes down to careful positioning of your lighting mainly. This is what's going to make all the difference, I would have thought.
 
Nice that you're in a studio - you can control the lighting and reflections much more easily. A few tips that may be of some help:

See if you can tell what kind of glass it is - plain glass is of varying quality but shouldn't present too much of a problem generally, although the cheap stuff may distort the image a bit. Non-reflective glass may produce a slight colour cast, (green/blue ish,) and may slightly soften the image you take, more than plain glass. Museum quality glass, (if the paintings are expensive,) is designed to reduce 90 odd percent of harmful light to prevent fading, and may well result in a strange colour cast too, but won't noticeably distort the image. However, none should be a major problem, its just handy to be aware, just in case!;)

If you don't want to shoot from directly above the painting, (which can be a pain,) I would stand the painting up at an angle of 45 degrees (ish!) on the floor against a stable prop, and support it at the bottom edge of the frame to stop it slipping. Set your tripod up so that the angle of the lens matches the angle of the picture facing you -ie: get it dead level and straight, minimising converging verticals etc.

I use two lights with soft boxes on, and position one each side of the camera, just in front and quite high, facing the subject in the middle so that they don't reflect in the glass. (Bounce them off large reflectors if there isn't any choice.)

Good luck! :thumbs:
 
The camera should be set dead center at 90 degrees to the plane of the picture and the LIGHTS should be placed at 45 degrees to the vertical plane of the picture on each side of the camera AT THE SAME HEIGHT of the camera. Skewing the plane of the painting will result in converging lines.

The focal plane and the plane of the painting should be exactly parallel.

If the image is small, you may get away with one light at an incidence of 45 degrees.

I think this clarifies Ian's explanation, unless I read it wrong.

I don't think I've ever seen class in front of any traditional media painting in any museum. The National Portrait Gallery here in London displays paintings without glass and illuminates them with incandescent lighting.
 
If you've got time buy a copy of Lgiht, Science and Magic 3rd edition and check out chapter 4 which covers this exactly.
 
When I took photos of maps and charts earlier this year, I had to use a pane of glass to flatten the pieces of paper as they were all curled up. To get around shooting through glass I made sure there was very little light coming into the room and used a long exposure to compensate for no light. This produced great results. I think the exposure time was about 4 secs.
 
Thanks to all for the information. I appreciate. When I win EuroMillions and buy my beach front property in Sicily you are all invited.
The shoot went well today and I probably found the most difficult part was getting the paintings parallel to the camera to stop any converging lines.
I didn't use any polarizing filters but instead used a black backdrop behind the camera to stop any reflections and shot with no ambient light on 1/125sec. Lights both softboxed at 45 degrees. I shot a color chart with every different painting to balance exposure and to colour balance at printing stage. The results looked good at this stage. Thanks again
 
To be certain of results and no reflections you should use cross polarisation.
Use lights at 45 degrees to the paintings with sheet polarisers on. This can be cut anf roughly held in place by lashing up something with cardboard and bulldog clips.
Use a polariser on the lens at 90 degrees to the lamp polarisation. You can easly check this by holding something metallic like a ring in front of the lens and turning the polariser until the reflections dissapear.

Measure exposure as incident light, manually set the camera and add 1.5 - 2 stops for the polariser and there you are! Perfect repros!
 
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