why UV filter?

[amade1974]

I am a bit confused. I was thinking of treating exposing some lenses to sunlight/UV light, in order to prevent any fungus from growing in them. Then somewhere here I read that glass absorbs UV radiation anyway, so treating the lenses with UV/sunlight would not do anything.
so, extrapolating from this: if glass absorbs most/all of the UV light, then why should we bother with a UV filter in front of the lens (besides protecting from the elements that is?).

THanks,

K

 

[chris00nj]

There are two camps on UV filters

One says that a UV filter can act like a protector against damage and can serve as a substitute for a lens cap (which you can't forget to take off)

The other camp says that adding another layer of glass can cause flare and reduce image quality.

 

[charjohncarter]

I don't understand half of this but if you read 4 or 5 times it might become clear.

http://photo.net/equipment/filters/

 

[Sonnar Brian]

Optical glass passes UV, just not the entire UV band. A Calcium Fluorite, Quartz, or Salt lens is required to pass deep UV.

Film is sensitive to UV. You are getting rid of the "Near UV" with a UV filter.

 

[maddoc]

As Brian said. A "UV" filter only blocks very near UV radiation and thus prevents from chromatic aberration by UV (lenses are only corrected for a limited part of the spectrum) and also filters scattered sun light that has a maximum in the UV region (Raleigh scattering), which can cause a blue tint.

 

[fixbones]

To me....

UV filter = transparent lens cap

 

[wolves3012]

To me....

UV filter = transparent lens cap

Seconded - it's cheaper than bashing or getting nasties on the front element of your lens! I'll suffer the marginal risk of flare from a modern filter.

 

[Chris101]

Seconded - it's cheaper than bashing or getting nasties on the front element of your lens! I'll suffer the marginal risk of flare from a modern filter.

You may be willing to suffer flare, but how about the denigration of your forum-mates. Maybe it's more prevalent in DSLR internet communities, but you would think that nobody could ever take a picture with one of them stuck on their lens. Apparently it wrecks the "eye que".

 

[bsdunek]

I use a UV filter when I need it - aerial photography, or hazy days. Also a haze filter which is similar. Of course I'm liable to use a UV or Skylight if I'm in a situation that could cause lens damage, such as in blowing sand or salt water.

 

[amade1974]

thanks! and thank you for the links. from the link that charjohncarter posted I understand now that lenses DO allow UV rays to go through, just not all going down to the low 200 nm range. IOW, the UV rays coming through will fool the film to think there is a lot more blue present than there actually is, and by doing so give the film an oversaturation in the blue color band.
I guess this also suggests I may be able to use sunlight/uv radiation to treat the lenses!
thanks again, this was very helpful!

 

[dwaoka]

serious uv exposure starts above 2000mtrs above sea level...