Condensation on front element

Last month we were shooting in the Rio Grande Valley in Texas and had

problems with early morning condensation on the front element of a

500mm f4. All the usual precautions were taken - avoiding dramatic

temperature changes by leaving the equipment in the vehicle, extending

the lens hood, etc. The humidity was very high and there was heavy

early morning dew. My question is, how can this problem be prevented?

And, if it can't be avoided, how would you recommend cleaning the

lens, other than with a microfiber cloth?

 

Thanks

You might try to find an add-on lens hood to extend the existing hood length. I use this technique for astrophotography. The inside of the hood is absorbant. I got mine from Orion Telescope Center. When not in use, the hood may be stored flat. Also, try not to aim the lens up when not in use. If all else fails, there are electric lens heaters (battery powered) to keep the condensation off, although this is usually not practical for normal photography. If moisture does get on the lens, there are battery powered "hair dryers" that are used to evaporate it (also available from astronomy supply centers). Obviously, keep the cap on the lens when changing environments, especially going from cold to warm. As you may have guessed, astrophotographers face this problem all the time. Good luck.

The key to your probem is that you left the lens in the vehicle. Condensation occurs when something cold is in a warmer, humid atmosphere. The key is to take the lens into the warmer overnight temps (hotel, tent, etc) and seal it in a plastic bag or something, then when you go out, it will be warmer than the ambient temp and will not have condensation.You might consider using an absorbent in the bag. Your problem is that the ambient temp was warmer than the lens as the sun heated the air. If equipment is not left in the vehicle and is sealed from humitidy overnight, then you would not have the condensation. Consider taking the camera body inside also. Seal it when taken inside overnight. You reversed the concept.

Remember, the glass taken out of the refrig gets condensation and the warm glass placed in a refrig does not.

I run into this problem here in the deep south quite frequently. If the sun is shining you might also just try pointing the lens into the sun for a few minutes. I often get condensation on my lens in the mornings if I am shooting in a shady spot, even if the lens is relatively warm. Pointing the front element into the sun will tend to dry up the condensation and warm the lens as well (ie. Dr. Bein's suggestion).

Just keep the lens warmer than the air and you'll never have this problem. How you do this depends on the situation but there's usually a way.

Thanks, guys! I guess we did have the process reversed. I thought the idea was to keep the temperature constant. We'll try it the new way. Thanks again!!

I would be very leary of pointing an un-capped lens at the Sun for several minutes, especially longer lenses, as the lens elements are great magnifiers, and this is potentially a good way to burn a hole in the shutter.

Kurt, unless I'm missing something, this shouldn't be a problem with the mirror down.

....and obviously don't look through the viewfinder!

Ryan: Good point. However, many years ago, on a sunny Summer day, my father left a manual, older Canon camera and its uncapped 50mm lens sitting lens-up beneath the Sun for a brief period of time, and damned if he didn't burn a hole in the shutter. I'm not sure how to explain this if the mirror was in fact down (the camera in question dated to the 1950's, and I have no idea if it offered mirror lock-up. If it did, my dad was unaware of this feature...); but I wonder--> with modern SLRs featuring "half mirrors", which I think have properties that both reflect light as well as allow some passage of light, I wonder if focused sunlight can quickly damage these mirrors and/or what lies beyond them, as well as more fully reflective mirrors? I have trouble imagining that focused, magnified sunlight is not also harmful in these instances. Anyone have any thoughts on this question?

Kurt.....certainly something to think about. Burning the shutter is something that can easily occur in Nikonos U/W cameras (no mirror). However, I have pointed my 300 f/4 at the sun quite a few times to dry up condensation (usually pointed towards the sun for a minute or less) and never had a problem. Of course the 300 f/4 certainly won't gather as much light as one of the faster telephotos. I guess if the lens was left too long there is a possibility of damaging the mirror or shutter. I would also be very interested in hearing if anyone else has experienced any problems with this. I'll certainly keep this in mind in the future!

I have to post a warning about equipment damage beside shutter burn: In the astronomy texts I've read (years ago, mind you) I have seen cautions about overheating the optics when pointing your what-have-you directly at the sun. These warnings were in conjunction with sunspot or eclipse observance. As I recall, the cement used for joining the elements together in a scope (and possibly a camera lens, as well) can be degraded by more than brief exposure to the extreme heat that concentrates in the optical path. Result? Your "groups" of lens elements spontaneously "ungroup." Eeek! I'd be grateful to anyone with more info in this regard.

 

To back-up what's already been said on condensation-fighting principles while I'm here: On my Navy sub, we kept the binoculars and hand-held camera gear in an electrically heated warming cabinet in the Control Room for use outside on the Bridge. Worked fine.

 

R/R~

Interesting point, Robert. By extension, I wonder if a focused beam of intense sunlight might cook the multicoatings of down-stream lens elements?

Mmmm . . . I have no idea about coatings. I know that the balsam used to cement lenses can be removed by heating the group on a hotplate (looening the cement, as the sunlight would) and then removing the residue with solvent. If the hotplate treatment is done intentionally, it would seem that coatings would survive heat - but I'm just guessing here: Maybe you don't heat coated lenses.

 

Anyone?

Well, a bit off the subject of the original post but I think I raised an interesting bit of information. I wouldn't think that too much heat would build up within the optical path as the heat is really generated at the point of focus (ie. close to the mirror or shutter). However, I am really just making a conjecture and would be glad to hear from someone who knows more about it than I do. Nontheless, I will certainly think twice about pointing a lens directly into the sun. As I'm thinking about it though, I wouldn't think that much harm would be done by pointing the lens into the sun such that the light falls onto the front element, so long as the rays are not shining directly into the lens (in the same manner as if you were shooting a photo into the sun). What do you think guys?

Dew is a depot (deposit?), so if you keep your lens pointing down between shots, you shouldn't have any problem. You lens barrel and camera will get wet but not the front element.

There is a kind of window-cleening spray that leaves a thin coating on the glass that prevents condensing. I tried it and it works. However I use it only when i'm going to shoot in circumstances that are extremely humid and with changing temperatures like bats in caves and foggy mornings. Furthermore, I apply it only on a nc-filter.

I also tried it on an aquarium when I used to shoot fish (with my camera !), when when tiny fish are close to the glass, you could see the coating on the slide.

 

Rollin

Erick, if the lens is a little cooler than the air you will get condensation no matter where your lens is pointed. Here's why. Warm air holds more moisture than cool air. If the lens is slightly cooler than the surrounding air, then an ultra thin layer of air just in front of the lens element will be slightly cooled. Because cool air can't hold as much moisture, the water vapor that was in the air just in front of the lens condenses out of the air onto the lens. It doesn't matter which way the lens is pointed, the water vapor has to go somewhere and it will condense on the lens, especially if it is humid.

Ryan: The heat is "really generated" 93-million miles away in the core of the sun! The temperature at any given point in your tube is a factor of how concentrated the sunlight is at that point and how quickly it can be dissipated. Letting sunshine warm the objective (front) glass at an oblique angle is unlikely to cause trouble.

 

 

Rollin: There are several such. I loved Rain-X for my car (when I had one!) Just drive 40mph and the rain blows off the windows! What is more, dirt and dust simply blew off as well. Anyone ever tried Rain-X on camera optics? (I'm frankly terrified!)

 

 

Gravity pulls on condensate: There is a bit more tendency for the heavier-than-air liquid water to accumulate on an upward-facing surfaces, especially if -- like glass -- that surface is impermeable and not saturated with water vapour the way fabric and wood can be. Even better if a long hood ("dew cap" in the astro biz.) can keep air from flowing freely around the lens face. This is my experience from early morning telescoping. Why not point the lens down for what slight good you can get out of it?

Hey, that goddamn Rainex was a menace, especially after it got dark and headlights came on--then, it was like your windshield had been WAXED, and visibility was then a really dangerous problem, especially if it was raining! As for decent anti-fog lens cleaning/treatment fluids, the only one I've found that leaves minimal residue and streaking is Photoclear Lens Treatment, marketed by Schneider Optics. Even then, things will still fog up if conditions are extreme enough.

RainX causes an increase in surface tension, causing rain to fly off

the windscreen of the car (thats the theory, seems to work for some people in some cars in some conditions - I like it). On a camera lens there is not the wind needed to clear the water off, so you just get droplets forming, which degrade the image.

 

There is another product (fogX) that reduces surface tension, causing the water to form a uniform film. It doesn't keep the glass dry, but it does prevent the individual droplets forming which is what causes the problem. Works great on bathroom mirrors, and I suspect on lenses or better, filters.

If you're still in or near your vehicle, turn your window defroster on with temperature set to heat, and point the front of the lens at the airstream coming from one of the vents. The condensation will disappear almost immediately, and there is no risk of scratching the lens.