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03-02-2010, 01:42 AM   #1
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lens filter

uv lens filter or Circular Polarizing Filter Lens Polarizer?

03-02-2010, 02:11 AM   #2
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QuoteOriginally posted by poogeek Quote
uv lens filter or Circular Polarizing Filter Lens Polarizer?
For What?

03-02-2010, 03:08 AM   #3
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QuoteOriginally posted by JeffJS Quote
For What?

k-x kit lens and tamron zoom lens 70-300.
03-02-2010, 03:38 AM   #4
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Your question doesn't quite make sense, these are two completely different filters and have two very different purposes.

UV lens is unnecessary and only used for protecting front element from damage. I always equip UV filter in front of my lenses no matter what. Some reason when I buy lenses from people who have had UV filter attached to it, it ends up being cleaner than those who didn't have one in the first place, I find that they keep better care of their equipment.

03-02-2010, 06:55 AM   #5
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QuoteOriginally posted by poogeek Quote
k-x kit lens and tamron zoom lens 70-300.
For what USE? Not for which lens.

Ben
03-02-2010, 03:16 PM   #6
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Right. A UV filter serves no purpose except to maybe protect the lens at the expense of some image quality (search this forum for any of the *hundreds* of existing threads on this). If you feel after reading those threads that you do wish to make that tradeoff, then you can leave the thing on all the time. A polarizer serves a very specific purpose - and Google should explain that pretty well. But you wouldn't want to leave the polarizer on when you don't need that effect.
03-02-2010, 07:20 PM   #7
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UV filters protect film from overexposure. Yours is not a film camera; digital sensors are pretty insensitive to UV light.
Uv filters protect lenses from flying crud. So, avoid flying crud.
UV filters enrich filter makers. So, buy stock in filter makers.
A UV filter makes a useful platform to hold tiny screws when you dismantle some device that has failed.
You can hold a UV filter in front of someone's mouth; if it fogs, they're still breathing.
So, UV filters aren't TOTALLY useless.
03-03-2010, 02:59 AM   #8
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QuoteOriginally posted by RioRico Quote
UV filters protect film from overexposure. Yours is not a film camera; digital sensors are pretty insensitive to UV light.
Uv filters protect lenses from flying crud. So, avoid flying crud.
UV filters enrich filter makers. So, buy stock in filter makers.
A UV filter makes a useful platform to hold tiny screws when you dismantle some device that has failed.
You can hold a UV filter in front of someone's mouth; if it fogs, they're still breathing.
So, UV filters aren't TOTALLY useless.
Very good!

Just the overexposure thing is not clear to me. Why would a UV filter prevent the film from overexposure? A UV filter lets most light just through and will only filter out wavelength of app. 420nm and smaller, which may lead to some unsharpness or somewhat foggy images, if there is excess UV light around (high altitude or very clear skies at the sea front). Only this excess UV light will be reduced and the detrimental effects (due to UV light not being properly focused by almost all lenses) remedied.

Ben

03-03-2010, 10:05 PM   #9
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QuoteOriginally posted by Ben_Edict Quote
Very good!
Thank you, thank you.
[/me buffs nails, poses]

QuoteQuote:
Just the overexposure thing is not clear to me. Why would a UV filter prevent the film from overexposure? A UV filter lets most light just through and will only filter out wavelength of app. 420nm and smaller, which may lead to some unsharpness or somewhat foggy images, if there is excess UV light around (high altitude or very clear skies at the sea front). Only this excess UV light will be reduced and the detrimental effects (due to UV light not being properly focused by almost all lenses) remedied.
Ah, UV light and film. The basic photo-sensitive emulsions created during the evolution of photography are ONLY sensitive to actinic (UV-violet-blue) light. Dyes must be added to emulsions for the film or plate to 'see' other colors. With B&W, and color transparency and print films, this sensitivity to UV remains. Hence UV filters, especially outdoors. We don't want to tickle those silver nitrate particles into forming a latent image of background noise, now do we?

Your assumption "only this excess UV light will be reduced" is incorrect; assuming the filter meets specs, ALL light/EMF below 420nm (or whatever the precise cutoff point is) will be cut. Look at the other end of the spectrum -- a 920nm or 1000nm UV filter removes ALL visible light, no matter its luminosity. I use such filters on a Sony NightShot P&S; scanning a viewscape of varying luminosity with NightShot OFF, the said landscape just doesn't show on the LCD screen.

Digital sensors put filters in front of each pixel, and the blue and green filters effectively blocks UV, so such sensors don't need added UV filtering. The red filters pass UV, which is why most digicams have an IR-blocking "hot filter" in front of the sensor. Digital and emulsions are overly-sensitive at opposite ends of the visible spectrum.

[Damn, I'm falling asleep again. Hope I didn't write anything stupid here.]
03-04-2010, 04:10 AM   #10
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QuoteOriginally posted by RioRico Quote
Ah, UV light and film. The basic photo-sensitive emulsions created during the evolution of photography are ONLY sensitive to actinic (UV-violet-blue) light. Dyes must be added to emulsions for the film or plate to 'see' other colors. With B&W, and color transparency and print films, this sensitivity to UV remains. Hence UV filters, especially outdoors. We don't want to tickle those silver nitrate particles into forming a latent image of background noise, now do we?

Your assumption "only this excess UV light will be reduced" is incorrect; assuming the filter meets specs, ALL light/EMF below 420nm (or whatever the precise cutoff point is) will be cut. Look at the other end of the spectrum -- a 920nm or 1000nm UV filter removes ALL visible light, no matter its luminosity. I use such filters on a Sony NightShot P&S; scanning a viewscape of varying luminosity with NightShot OFF, the said landscape just doesn't show on the LCD screen.

Digital sensors put filters in front of each pixel, and the blue and green filters effectively blocks UV, so such sensors don't need added UV filtering. The red filters pass UV, which is why most digicams have an IR-blocking "hot filter" in front of the sensor. Digital and emulsions are overly-sensitive at opposite ends of the visible spectrum.

[Damn, I'm falling asleep again. Hope I didn't write anything stupid here.]
You did not write anything stupid. But anyway, nearly every photographic lens already fullfills the purpose of a UV filter, as standard glass + coatings have a low transmission in the UV range. The "optical window" of standard glass only starts around 350nm, which is also the cutt-off range of those UV filters that actually work! (nice test here: Filters - UV or not UV? - photo.net)

You need special "super-achromatic" or Apochromatic lenses with extended transmission to really make use of the UV part of the light.

Also, in traditional BW emulsions (silver halide), the silver halide obviously will absorb UV photons, but it will not form an image! This is simply due to the fact, that a most lenses will not focus UV light. What you get is an unfocused "UV noise" overlaying the whole image, which can be detected as unsharpness and loss of contrast. But as I wrote above: as lenses already absorb most UV, this "UV noise" is completelöy negligible, except for severe UV conditions.

The only point in your post I questioned was the "overexposure" thing. There is no overexposure caused by UV light. I have never used UV filters on my lenses in film days, except at high altitude in the snow or as a lens protection at thwe sea shore, my images never turned out overexpsoed by UV radiation - and I have never heared or read any indication for that being the case. And I guess, what I wrote above, pretty much explains, why there can't be UV-caused overexposure.

Ben
03-04-2010, 06:18 PM   #11
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QuoteOriginally posted by Ben_Edict Quote
The only point in your post I questioned was the "overexposure" thing.
Not to be pedantic (who, me?) but I never mentioned overexposure; that was in the quote to which I responded. And yeah, most modern lenses block UV. So for more serious actinic light work, I have to put ancient lenses on bellows. Like my WWI-era Gundlach Turner-Reich Anastigmat 12" f/7, or at least its front element. (The whole assemblage weighs almost a kilo.) I also put old enlarger lenses on bellows, for both macro and distance shooting. I think those are also uncoated, but I haven't mapped their spectral transmission curves. Guess I'm not serious enough yet.
03-05-2010, 03:43 AM   #12
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QuoteOriginally posted by RioRico Quote
Not to be pedantic (who, me?) but I never mentioned overexposure; that was in the quote to which I responded. And yeah, most modern lenses block UV. So for more serious actinic light work, I have to put ancient lenses on bellows. Like my WWI-era Gundlach Turner-Reich Anastigmat 12" f/7, or at least its front element. (The whole assemblage weighs almost a kilo.) I also put old enlarger lenses on bellows, for both macro and distance shooting. I think those are also uncoated, but I haven't mapped their spectral transmission curves. Guess I'm not serious enough yet.
Sorry, if I got the overexposure thing wrongly. It is in post No. 7 and wasn't marked as a quote.

This Turner-Reich sounds interesting. What fl do you get with just the front element?

I have an older Symmar convertible (300/5.6 and 500/12) and its weighs a ton, though the newer - non-convertible 300/5.6 (which for some reason I also happen to have) is probably about the same. My old Schneider-Kreuznach Apo 600/9 is so heavy I dare not use it on my Crown Graphic, wich currently is my preferred 4x5 for field use. i couldn't focus to infinity anyway on the Crwon...

Ben

Last edited by Ben_Edict; 03-05-2010 at 08:23 AM.
03-05-2010, 05:46 AM   #13
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Wondering what poogeek is making of this whole discussion Where is he/she, by the way
04-30-2010, 11:51 PM   #14
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QuoteOriginally posted by sterretje Quote
Wondering what poogeek is making of this whole discussion Where is he/she, by the way
hahaha... i dont understand anything... whoooo.... got to read more....
05-01-2010, 09:25 AM   #15
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QuoteQuote:
Some reason when I buy lenses from people who have had UV filter attached to it, it ends up being cleaner than those who didn't have one in the first place, I find that they keep better care of their equipment.
That could work backwards, too. People "think" they are all set with a piece of glass in front of their lens, and then don't worry about saltwater spray or dust, etc., getting around the other parts. People without a filter may take better care of the lens in general for that very reason.
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