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Fogging

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/24/2009 at 01:28
chomHD View Drop Down
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Do all binoculars fog on the outside of the eyepiece lenses when it's cool out? Mine do. I'm guessing it is the warmth coming from my eyes. It is really irritating and I'm willing to buy a different pair that don't do this. I don't think getting nitrogen filled binoculars would help since the fogging is on the outside.
 
I have the Nikon Action VII binoculars and I chose those over the Bushnell Legend and was wondering if I made the wrong choice.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/24/2009 at 06:29
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Yep, that is called condisation. It is fogging when that happens on the inside.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/24/2009 at 09:59
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Yeah, they all due that I dont think there is any way around it.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/24/2009 at 14:48
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When moving from a very cold environment to very warm, humid, you get condensation, and vice versa.  Fogging occurs in scopes, in the above described conditions, that have either not had or lost their gas purge. Nitrogen is not very susceptible to temp change, noble gases (such as argon/krypton) less so.  For MOST applications, nitrogen is sufficient.  Where very rapid temp changes occur, noble gases are required.  While noble gases MAY extend the life of a scope, if there is any price addition to a scope's cost due to noble gas vs nitrogen, it is probably not worth it.  There are exceptions, but for the most part, game hunters are not in that category of exceptions.  

As an aside, I've noticed that Rainguard (or similar) equipped scopes are less susceptible to condensation effects.  They clean up more easily and the effects are less pronounced... at least in my experiences.  I don't own one, but have used them on occasion and have friends who do have them.  


Edited by Kickboxer - May/24/2009 at 15:02
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/24/2009 at 16:50
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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/25/2009 at 14:36
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Yes, and it works pretty well for most conditions.  More extreme conditions can still defeat it, though.  It is a great product for most applications.  It definitely reduces susceptibility to condensation.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/25/2009 at 22:34
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If it's indeed occurring on the OUTSIDE lens surfaces, it's condensation, and it will happen to any optic with rapid changes in temperature.  Some of the hydrophobic coatings added to lenses may cause the condensation to bead up and run off the lenses faster, but the development of condensation is basically unavoidable with rapid changes in temperature & moisture.

If, on the other hand, it's occurring on the INSIDE of the optic, and if the optic is supposed to be waterproof & fogproof, then you need to send it back to the manufacturer for repair.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/26/2009 at 11:55
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I always try to give my optics time to acclimate themselves - aka - put them in my truck overnight to get used to the hot or cold for the next day's hunt.  Keeping them indoors and then taking them outdoors will almost always produce the foggy problem, unfortunately.
 
Better glass has FEWER problems because of the coatings, but will still fog up because of temperature.
 
I hope this helps.
 
J
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/30/2009 at 20:09
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Originally posted by Kickboxer Kickboxer wrote:

Nitrogen is not very susceptible to temp change, noble gases (such as argon/krypton) less so.  For MOST applications, nitrogen is sufficient.  Where very rapid temp changes occur, noble gases are required.  While noble gases MAY extend the life of a scope, if there is any price addition to a scope's cost due to noble gas vs nitrogen, it is probably not worth it.  There are exceptions, but for the most part, game hunters are not in that category of exceptions.

I see your signature is "Opinion, untempered by fact, is ignorance." ;)

Optics fog internally because water vapor condenses onto the cold optics.

There is no difference between fill gases for fogging so long as all are dry. 

The marketing blurb is the argon leaks away more slowly (because it has a higher molecular weight of 40 rather than nitrogen 28 ... so the argon will last longer in fact 40/20 squared longer because it will diffuse through small holes more slowly). This leads to a more interesting argument about why these sealed bins aren't actually really sealed. And it seems that the Top 4 bins (and a few pretenders) still use nitrogen because it works fine. Caveat emptor. If I'm gong to have leaky bins then I think I'd prefer SF6 fill ... that would take a while to leak out.

And as Dutch birder reviewer (tvwg.nl) have shown some fresh off the shelf nitrogen/argon filled optics will fog in very cold weather (say -20C) because the fill gas wasn't dry. 

The dryness is the key. 

If they filled the bins with dry air it would be fine. The roof prisms silver mirror coating might oxidize slowly but they wouldn't fog ... that's why they don't use a fill gas like air that has oxygen in it. Though if you had a dielectric mirror (that has no metal on it) then it wouldn't actually make a difference.

Unless you are using your bin at below 77K (-196 C) you won't have a problem with dry nitrogen fogging in your bins. Dry argon filled bins will fog a little bit higher temp (in the eighties K).
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/30/2009 at 20:28
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