Using a Polarized light source for copying...

[Steven Barall]

Hello everyone. I am going to photograph many paintings and other framed flat art in the next week or so. I understand about using that Rosco polarizing gel filter material on the lights but my question is do I then just use that same filter material in front of the lens but just turned at a right angle or do I use a standard glass rotating polarizing filter on the lens?

Also, can I diffuse the lights and also use the polarizing material on them or does the diffusion ruin the polarity of the light? Thanks to everyone in advance.

[Bob Salomon]

You use a standard camera type polarizer, not a lighting grade one. The axis of all 3 polarizers must be aligned the same way.

[Greg Lockrey]

You use a standard camera type polarizer, not a lighting grade one. The axis of all 3 polarizers must be aligned the same way.

I find that the axis of the camera filter should be "crossed" to the axis of the lighting filters. (See Kodak's "Copying and Duplicating"). This way all glare is eliminated. You can very easily see the effect in your viewfinder.

[Steven Barall]

Thank you all very much. Cheers.

[Bob Salomon]

The easiest way to set up the lights and the camera filter is to set up one light and the filter on the camera. Place the polarizing foil on the first light and have someone rotate it till you see the maximum polarization on the camera. Turn that light off and turn the second one on. Place the foil on that light and rotate it till you see maximum polarization in the camera with that light. Take a permanent marker and mark the foils and the lights so you can take the foils on and off and always have the proper orientation. If you have a Heliopan polarizer note the position of any number on the rim of the filter and always put the filter back on the camera with the number in the same position. If you have an uncalibrated rim then make a mark on it to indicate the proper position.

if you end up photographing objects that has gold, silver or platinum and you photograph those precious metals under totally polarized lights then the precious metals will come out black. So if you have gold foil frames be careful if they are part of the copy.

[W K Longcor]

Also ___ if you are photographing paintings - particularly oil or acrylics that have some " thickness" to the paint - you may not want to fully polarize the light. The artist will have painted the image , allowing for surface reflection. Total polarization of the light -- will make the image look far too contrasty and color much too intense -- so watch the surface and rotate the camera filter off of the fully polarized position.( I learned this from teaching photography at a professional art school -- artists can be every bit as fussy as photographers!).

[CG]

... my question is do I then just use that same filter material in front of the lens ...

Use only camera grade filters over the lens - usually that would be the familiar threaded filters. The polarizing material used over the lights is not optically good enough to be in the image path - but is just fine for illuminating the subject.

C

[CG]

Also ___ if you are photographing paintings - particularly oil or acrylics that have some " thickness" to the paint - you may not want to fully polarize the light. The artist will have painted the image , allowing for surface reflection. Total polarization of the light -- will make the image look far too contrasty and color much too intense -- so watch the surface and rotate the camera filter off of the fully polarized position.( I learned this from teaching photography at a professional art school -- artists can be every bit as fussy as photographers!).

The above is often true, but not always. I shoot my own paintings, which are extremely textural, and do not want any surface glare whatsoever. When I want to emphasize the texture, I light to create shadow revealing the depth of the paint. I never want highlights to show depth, since that also reduces the saturation of the color there, and I'm verrry picky.

Best to test and find what works for your application. Crossed polarizers give you wonderful control.

C

[W K Longcor]

The above is often true, but not always. I shoot my own paintings, which are extremely textural, and do not want any surface glare whatsoever. When I want to emphasize the texture, I light to create shadow revealing the depth of the paint. I never want highlights to show depth, since that also reduces the saturation of the color there, and I'm verrry picky.

Best to test and find what works for your application. Crossed polarizers give you wonderful control.

C

You've made my point - better than I did. Artists are fussy and picky about their work ( as well they should be). I should have capitalized -" MAY not want to". And, I'll repeat another thing you said -- "Best to test and find what works for your application." Rotate the filter and see what gives the look you are after.

[Murray]

What kind of polarizers tolerate the heat of lights? Or, rather, how much heat do various polarizers tolerate?