Filter fogging

[Charles Twist]

On a cold start this weekend, I was plagued by fogging as the temperature rose and the frost thawed in the early sun. I had sensibly left the gear in the van overnight so as keep it at working temperature to avoid condensation. Lenses and camera didn't fog up but the resin filters, especially the less expensive hitec ones, were sucking moisture out of the air quicker than I could mop it up and re-adjust. Does anybody have a neat trick to avoid this problem? Or is there a hydrophobic film one can apply?
Thanks,
Charles

[IanG]

There's a silicone liquid that people use, I was given some way back in the late 1970's by a friend who also worked for me and we'd use it on glass filters ocassionally. I think I still have it somewhere but it was a small unlabelled bottle. He used it to stop problems with his glasses fogging up.

Not sure how good it would be on resin filter.Divers use a silicone spray to hel keep their goggles from misting up. Remember that they dye many of the resin filters so they must be permeable to a slight extent.

Ian

[dave_whatever]

If you had moisture condensing on filters then they were too cold, maybe don't leave them in your van. I've only ever had lenses/filters spontaneously fog when taking a camera out of an airconditioned room into the sweaty tropical atmophere of thailand.

[Dave Tolcher]

I have had this problem big time whether straight form the car or already pre chilled, only reliable answer was to use a lens hood. If I put on the lee lens hood and used the filter slot then they didnt fog. Riddle me that one.... I havent questioned the why but it has solved my fogging problem in the circumstances you describe completely.

[Charles Twist]

Thanks everyone for your input.
Cold gear helps by not having immediate condensation, but the problem is very much due to the heating up of the air as the sun stirs in to action. The idea of a gel (maybe one for divers' goggles?) is good and worth investigating even though the absorption of the material might be an issue. There is also a technique called plasma polymerisation which would be available to larger companies (with lolly) to coat their filters with a thin hydrophobic layer. Might be better for the optics...
In the meanwhile, Dave's solution sounds very straightforward even if the theory is less than clear.
Regards,
Charles

[Joanna Carter]

I think Dave's solution works by stopping air movement past the surface of the lens/filter, but that could be simply an educated guess

[Dave Tolcher]

Science is unlcear but I found it works when effectively there is still dew forming on all surfaces. Mocking is very much allowed but it *has* worked very effectively for me in both dew and frost conditions

The other alternative is that good old rain solution and use a filter in front of the filter and remove it just for the exposure. Draping your dark cloth over the front and removing just for the exposure also works well.

[Paul Dunning]

Or you could just embrace it and enjoy that dreamy soft focus effect fogged filters give

Seriously though, my guess would be that your gear would be warming up at a much slower rate than the air around it thus causing the moisture in the air to condense on the filter. This would suggest that you actually want to try and keep things warmer than the ambient temperature to avoid fogging. Personally I've never found a satisfactory solution other than to give the filter a wipe before each shot.

Paul.

[Thingy]

Divers use a silicone spray to hel keep their goggles from misting up.

In the 1980s divers used saliva. Nuff said.

Perhaps what is needed is special, heat conductive, Lee glass filters with a heating element round the edge, like you get in cars, operated by a 9v battery. We could call it a Twist Filter!

[Joanna Carter]

Perhaps what is needed is special, heat conductive, Lee glass filters with a heating element round the edge, like you get in cars, operated by a 9v battery. We could call it a Twist Filter!

Actually, if you could get hold of a battery hair dryer…

[Dave Tolcher]

Perhaps what is needed is special, heat conductive, Lee glass filters with a heating element round the edge, like you get in cars, operated by a 9v battery. We could call it a Twist Filter!

Actually, if you could get hold of a battery hair dryer…

Sounds like a girly thing to me.