Lens fogging

[Kurt]

I'm having dramas with lense fog the past few outings; since I freedive with my camcorder, I'm not sur ewhether it is because I'm going constantly between two distinct temperatures (warmer surface water and cooler bottom water). However, it only seems to start after I've been using the camera for a while..so I thought it may be a result of heat being generated from the camera???? I have tried using silica packs but to no available, any suggestions? Would anyone use mask defog on the inside of the lense, or will this damage it?
Kurt

[Diver John]

G'Day Kurt!

Whilst I am not an expert I have found the following information which maybe useful for you at http://www.urprofilters.com/content.do?region=TechTalk :

FOG can collect on ANY lens surface. It restricts vision, impairs safety, and inhibits photography and videography. Fog can even render anti-fog coatings ineffective.
Fog is caused by a very small electro-statically charged particle which attracts a particle of water vapor. These microscopic particles attach themselves to most glass and plastic surfaces. The particles are typically composed of airborne dust, smoke or sediment and minerals found in fresh and salt water.

When the temperatures of the air and/or surface of a lens drops, "invisible" water particles condense into liquid water vapor. Electro-statically charged particles are the center of the water droplets. This vapor forms a thin - but visible - layer ON TOP of a camera lens camera port, or dive mask ...even ON THE SURFACE of a perfectly functioning anti-fog coating!

PREVENT FOGGING
Spectrum Technologies' FOG-GONE lens cleaning solution is formulated to REMOVE and DISSOLVE the microscopically thin fog-causing-layer of electro-statically charged particles. FOG-GONE is safe to use on ALL coated and uncoated optical plastic and glass lens surfaces.

I also found a product available in Australia at : http://www.underwater.com.au/shop.php/department/photographic-accessories
called "Moisture muncher" which reportedly "Absorbs moisture to prevent fogging and corrosion".

I hope this is of some help. We look forward to seeing some of your shots! Happy filming!

[kater]

good answer, john. Seriously. How good are you? I've also tried (and not always successfully or easily) flushing tank air through a housing as it is filtered and dry, so if you are in a humid environment (like, oh, solomons, fiji, vanuatu - you know, all those places we like to pretend we're diving on the weekend) -it seems to help a little. I've also heard if you fill the housing with water, there is 0% chance of fogging.

[Diver John]

Good idea Kate! There would be few cameras that would be able to handle the water in the housing though... If you were using a camera that is waterproof then you could fill the housing with freshwater and I'd imagine the photos would be fantastic!