# Some general questions about lens filters for a 35mm SLR

**URL:** <https://boards.straightdope.com/t/some-general-questions-about-lens-filters-for-a-35mm-slr/283406>\
**Category:** Factual Questions\
**Created:** [January 6, 2005, 4:37pm UTC](https://boards.straightdope.com/t/some-general-questions-about-lens-filters-for-a-35mm-slr/283406 "2005-01-06T16:37:46Z")\
**Posts on this page:** 4\
**Page:** 3

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [January 7, 2005, 7:15pm UTC](https://boards.straightdope.com/t/some-general-questions-about-lens-filters-for-a-35mm-slr/283406/41 "2005-01-07T19:15:24Z")

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> [@Padeye](#):
>
> **Q.E.D.** , I could be wrong but I don’t think a standard UV has a Wratten number, at least I’ve never seen one.

I just did some searching and found that 18A is the Wratten number of the transparent UV filter. For some reason I though it was 1A. So, there you have it.

BTW, interesting about the cornea filtering out UV that would otherwise be detectable to the retina. What color does the brain perceive UV as, did they mention? I’m guessing a deep violet.

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**Author:** ![AncientHumanoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ancienthumanoid/32/278_2.png) [@AncientHumanoid](https://boards.straightdope.com/u/AncientHumanoid)\
**Post date:** [January 7, 2005, 7:23pm UTC](https://boards.straightdope.com/t/some-general-questions-about-lens-filters-for-a-35mm-slr/283406/42 "2005-01-07T19:23:15Z")

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[Here’s some fun info](http://www.geocities.com/thombell/curves.html)  
And the book is _Kodak publication B-3, KODAK PHOTOGRAPHIC FILTERS HANDBOOK._ Available [here.](http://www.amazon.com/exec/obidos/tg/detail/-/0879856580/103-3651366-0118251?v=glance)

Figures UV would have a wratten #. I’ve never seen it printed on a threaded filter, tho. Most of the other colours are avaible in threaded glass filters from almost anyone in addition to the Kodak gels. The same #s are used for astronomy as for photography.

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**Author:** ![AncientHumanoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ancienthumanoid/32/278_2.png) [@AncientHumanoid](https://boards.straightdope.com/u/AncientHumanoid)\
**Post date:** [January 7, 2005, 7:31pm UTC](https://boards.straightdope.com/t/some-general-questions-about-lens-filters-for-a-35mm-slr/283406/43 "2005-01-07T19:31:17Z")

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Sorry, **Padeye**. I’m not ignoring you, just missed your post in that last flurry of activity and board wonkiness.

Your point is well taken, thanks, but I think you know what I meant. 😉

Also, looks like I won’t need to post a comprehensive lsit, as everyone seems to be finding one on their own.

Board traffic must be high right now, so I’m just going to go over here for a little while…

[leaves to actually outside for a while]

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**Author:** ![Zebra](https://avatars.discourse-cdn.com/v4/letter/z/c0e974/32.png) [@Zebra](https://boards.straightdope.com/u/Zebra)\
**Post date:** [January 7, 2005, 7:46pm UTC](https://boards.straightdope.com/t/some-general-questions-about-lens-filters-for-a-35mm-slr/283406/44 "2005-01-07T19:46:21Z")

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> [@Cartooniverse](#):
>
> Gee, **Zebra** , didn’t know you were into photography…and there we were at the photo exhibit at MOMA !!
> 
> Cartooniverse

Well, you and **Eats\_Crayons** know what you’re talking about whereas I…

Well, I started this thread didn’t I.  
Thanks everyone for all the great info.

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