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| Cross polarized lighting for paintings http://paulcbuff-techforum.com/viewtopic.php?f=8&t=299 |
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| Author: | purtypitcher [ Sun Feb 21, 2010 3:51 pm ] |
| Post subject: | Cross polarized lighting for paintings |
I'm experimenting to see how the cross polarizing method works before I get some good new lights, and I am leaning towards strobes and the awesome Einsteins. I have been experimenting with a couple of old Smith Victor lights with 250 watt ECA bulbs, and some homemade polarizing filters to create the polarized lighting for photographing glossy oil paintings. The polarizing film is sandwiched between cardboard sheets with an aperture of about 13 inches, which is suspended about 5 inches in front of the lights. It only takes 15 seconds of "on" before the polarizing film starts buckling and I turn everything off. If I use the Einsteins and their 250 watt modeling lamps, am I going to have the same heat problem? Is there some way of mounting a polarizing film further out from the monolight? Is polarizing film more heat sensitive than other colored gels? What would be the best way to mount some polarizing film to your 8.5 inch reflectors? Are there some other questions I should be asking? Thanks for any advice, I am debating between continuous and strobe lighting, and am looking for good reasons to go Einstein. Don |
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| Author: | Luap [ Mon Feb 22, 2010 12:51 am ] |
| Post subject: | Re: Cross polarized lighting for paintings |
I would use them with the modeling lamps off. Then you won't have a problem with heat. I've used them clipped right to the front of standard 7" reflector. A layer of diffusion gel beneath the polarizing filter will yield less chance of hot spots. |
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| Author: | purtypitcher [ Mon Feb 22, 2010 8:06 am ] |
| Post subject: | Re: Cross polarized lighting for paintings |
That would be good for making the photos, but I would still need modeling lights to get the lighting even, adjust polarizers on lights and lens, etc. Are there other types of polarizing films that don't start to melt after a few seconds of modeling light heat? Don |
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| Author: | Technical Support [ Mon Feb 22, 2010 10:44 am ] |
| Post subject: | Re: Cross polarized lighting for paintings |
You never mentioned which brand gels you use, but Rosco and Lee are both well regarded companies. You should contact the gel manufacturers for the suggested output limits. That being said, you can also dial the output of the model lamps down, thus reducing heat, and keep a higher output on the flash tube. This can be done from the back panel of any of our lights, except the Bees, and with all of our lights via the Cyber Commander. |
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| Author: | purtypitcher [ Mon Feb 22, 2010 12:22 pm ] |
| Post subject: | Re: Cross polarized lighting for paintings |
I bought a 17 x 36" piece of film from a Texas company, they call the brand Alight. I'll check with them regarding heat. They also sell a semi rigid 30 mil laminated version which might take care of my buckling problem. I've read that polarizing film in general can be quite heat sensitive. Glad to hear the modeling lights can be dialed back independently on the strobes, that might be the best solution. Don |
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| Author: | Voyager13b [ Tue Feb 23, 2010 2:47 am ] |
| Post subject: | Re: Cross polarized lighting for paintings |
You can try a sheet of "heat absorbing" glass between your modeling lamp and filter gel. That can take the hit of the longer heat producing wavelengths of light, but not for too long without help. If you don't provide cooling, the glass will either overheat, or re-radiate long waves because of it's own elevated temperature. Still, it should be fine for your needs, as setup should only take a few minutes at a time. There are many sources of that type of glass, but sheets made for protecting film from buckling in enlarger heads might work well with your case. They cost less than $50, as I recall. Depending on the size of the glass sheet, you have to come up with a workable clever solution for mounting it for best effect, but thats part of the fun... Voyager |
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