Polarising film.

Craig Gerard · Post by **Craig Gerard** » Mon Aug 16, 2010 9:18 pm

Polarising film.

I purchased a B&W MCR Circular polarising filter for my camera lense and was looking for some polariser film to attach to my light source for the purposes of cross-polarisation.

Would the items below be useful on the flash head(s) for cross-polarisation when used in combination with the polarising filter on the camera?

http://cgi.ebay.com/Polarizing-film-LCD ... ra_Filters

http://cgi.ebay.com/Polarizing-film-LCD ... ra_Filters

Craig

elf · Post by **elf** » Mon Aug 16, 2010 9:52 pm

They should work fine. I'll let you know for sure when mine arrive

Craig Gerard · Post by **Craig Gerard** » Mon Aug 16, 2010 11:26 pm

elf,

That's good; yours should arrive before mine

Craig

Ulf W · Post by **Ulf W** » Tue Aug 17, 2010 4:03 am

Hi,

I think these materials are a bit heat sensitive as they use a plastic base. If the light sources are too hot the can degrade and melt.

I remember an experiment I made a long time ago, putting a camera Pol-filter in front of my projector. That filter isn't good anymore.
It is a Hoya filter with the polarizer film mounted between glass. The center area is pale and do not polarize anymore.

/Ulf

Craig Gerard · Post by **Craig Gerard** » Tue Aug 17, 2010 4:26 am

Ulf,

Thankyou for sharing your experience. Yes, they would be heat sensitive and can degrade.

I recall AndrewC referring to a 'bleaching' effect when using similar material on flash units.

Lee Filters make polarising gels; but they are rather expensive and I'm not sure about their longevity either?

The ones on eBay are cheap and should be good to experiment with, whilst keeping in mind the limitations and precautions you have mentioned.

Craig

elf · Post by **elf** » Sat Aug 28, 2010 7:20 pm

The filters have arrived and I have mounted them on the flashes. The mount is rather crude at this point, but I want to see if the polarizing filters will make enough of a difference to spend more time on the mount. Version 2 will probably be all acrylic and be able to use other gel filters as well.

The only remaining problem is how to mount a 58mm circular polarizer in front of the reversed macro lens and the JML 21 mm

Craig Gerard · Post by **Craig Gerard** » Sat Aug 28, 2010 7:28 pm

elf,

Thanks for the followup. My samples have also arrived.

I like the speedlight filter mount

A 58mm CPL on a 21mm/3.5 JML could be tricky. I purchased a 28mm CPL from the Orient. Looks good enough for this exercise.

I'm going to point it at some ice cubes

Craig

elf · Post by **elf** » Sat Aug 28, 2010 8:56 pm

I had forgotten that I made a reversing adaptor for an El Nikkor 80mm f5.6 lens a year or so ago. It happens to have 52mm threads, and I also have a 52mm to 58mm step up ring, so it all fits together well. First test looks promising.

Here's a shot of the adaptors.

elf · Post by **elf** » Sun Aug 29, 2010 4:12 pm

Here's a couple of test images with twin flashes. The only change between images was rotating CPL 90 degrees. Key light is on the right about 3:00 oclock and fill light on the left at 11:00 oclock. Both slightly in front of the subject.

Minimum polarized

Maximum polarized