Re: Fogging Camera Lenses - Problem?

[Adam Cudworth]

This is only a problem if moisture is present on the lens or inside the lens casing. For example, if you fly the GoPro with the protective casing on - it will most likely fog up as the air trapped inside the casing contains moisture. If instead you fly it without the protective casing on and just 'naked' then it will be fine.

I had a problem recently with fogging when flying the gobandit video camera - this was due to moisture trapped inside the lens casing. 

2 solutions: either pop in the 'anti-fog' patch which effectively absorbs the moisture; or remove the 'waterproof' lens casing thereby allowing the moisture to escape.

If you have a certain camera in mind that you want to fly, I would recommend posting it here or on the IRC to see if anyone else has flown it before and potential problems can be highlighted etc.

Adam 

On Friday, November 30, 2012 8:25:18 PM UTC, HansSolo wrote:

I'd have thought that a camera lense would fog up / freeze at altitude, is this the case?

What can be done to prevent this..... If indeed it is a problem.

Thanks

Hans

[Liz Henriquez]

In addition to using the anti-fog patches, we flush our GoPro cases with CO2 prior to putting the camera in. This removes the moisture as well as insulates the batteries. Very easy - use a large zip loc bag and a paintball cartridge. If anyone wants more specifics, please let me know

Liz Henriquez

Project Aether

USA

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[Anthony Stirk]

Sorry to disagree on this but GoPro cases are great at keeping outside pressure out but they aren't sealed so well the other way.

The result is the pressure drops in the case and any moisture in those antimist strips boils and condenses on the coldest part which is generally the lens.

The advice is if you want to fly GoPro do so with the open case or no case at all and don't use the antimist strips.

Anthony M0UPU

Sent from my iPhone

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[Steve Aerospace]

Thats my experience too - pressure drops in the GoPro cases (very difficult to open when they reach the ground) and the anti-fog strips release any moisture they have absorbed. 

I almost exclusively use the GoPro HD 1 or 2 with no case.  The only exception was a recent job where the case was needed in order to get the exact picture geometry that the customer wanted**.  In this instance I flushed the case with Helium.  I placed the camera in an open case inside a sealed plastic bag. Then I evacuated the bag and part re-filled with helium and closed the case from the outside of the bag.  The sealed (helium inflated) bag and camera+case contents were transported to the launch and only taken out minutes before flight (to reduce any diffusion).  Even then I got some mild fogging for a small portion of the flight - fortunately fully clearing before the required apogee shot.  I didn't get to the bottom of that (suggestions?) - but since I have no plans to use the case again it doesn't matter.

Steve

**The lens in the GoPro 1 & 2 case changes the focal length and field of view of the camera.

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Steve Randall

Random Engineering Ltd

st...@randomaerospace.com

+44 7802 242135

[Postbotenamt]

If at all, they'll fog/freeze on the way down. To prevent fogging you
could try to fly on a day with low humidity in the air.

Best regards,
Luke

[Justin Maynard]

We recently flew quite a few Go Pro 3's in cases with desiccant strips. No problems with fogging but, several did stop recording so we think they are not as temperature resilient as the GoPro 1 & 2. Just repeating suff from my launch report but though it a good place to mention it again. 

Justin 

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[Anthony Stirk]

Hi Trevor

Its not the temperature its the pressure. The internal pressure equalises with the outside pressure the boiling point of water is reduced and all the moisture in those antifog strips boils off and condenses on the cold part which is generally the lens. This had a water proof case and antimist strips and was extremely hard to open when we got it back :

http://www.youtube.com/watch?v=KGLB9-LdpYM

Anthony

On Wed, Jan 2, 2013 at 9:15 PM, Trevor Cousins <trevor_...@yahoo.com> wrote:

I've had the gopro2 in the freezer a few times. It's -20C in there. The 2 batteries (the bacpac battery is one of the two) last about 3 hours. The case is the waterproof one. The ant fog strips do work. After 2 hours the camera is above zero. Removing the bac battery the temperature on the back of the main battery is about +16C.

TC

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[Anthony Stirk]

If you're launching a GoPro you have to be aware there is a chance you're not getting it back. However if you really really have to launch with the case on don't put the strips in, and flush the case with Helium just before launch and fingers crossed.

Anthony

On Thu, Jan 3, 2013 at 8:32 AM, Trevor Cousins <trevor_...@yahoo.com> wrote:

Hmm. I see what you mean and I started writing a reply but then stopped.....it has nothing to do with the air (I know common sense says it does). Gases exist together completely sepearately (remember Partial Pressures) so the amount of vapour the silica gel absorbs does not depend on the air, it depends only on the amount of water vapour floating about.

With dry silica gel the water molecules floating about have a lot of landing room on the surface so they do and that make for less vapour. The gel exists in equilibrium with the vapour, like all surfaces.

BUT regardless of what I just said you central argument is right I think (if this is what you were implying) that the silica gel is a SOURCE of vapour - it is contributing more than it took from the air. If this is right then either the strips have to start out super dry. If they are not super dry then they would be worthless. So put them in the camera when they are hot!

It's hard to test this. The only certain solution is the purge the air (and vapuour) from the casing.

I neeeeeeeed to have the waterproof case.

TC

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[Steve Aerospace]

I would agree with that - or you might want to try some other gas that is known dry.  I recently used the helium flush technique on a GoPro + case.  I was reasonably scrupulous about ensuring it was properly flushed - including vacuum pumping out the case and camera before re-filling with helium and closing the case. This was all done inside a sealed thick plastic bag.  Even then I got a little condensation for the early part of the flight - I can only assume:

a) water vapour crept in somehow - perhaps there is an exchange as the helium leaks out of the case as the pressure drops.

b) there was still some air+water trapped inside the camera lens assembly that didn't come out under vacuum.

c) there was some water vapour present in the helium

The gas spec for high purity (99.997%) helium shows 3.5ppm water - so the rather less pure balloon gas we use might have more.

Steve

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