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11-20-2009, 01:38 PM   #16
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QuoteOriginally posted by wallyb Quote
B
A UV filter of reasonable but CHEAP quality will NOT affect your lens' image quality in any noticeable way. Optics do not work like that, and it's even more unlikely the longer the focal length of the lens.
I don't think it is wise to take advice from someone who obviously does not know much about optics.
Imperfect filters have more effect on long lenses !

11-20-2009, 01:39 PM   #17
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I have never purchased a UV filter.

I have used high-quality UV filters when they came with a used lens I purchased.

I have never seen any degrading effect on my pictures (nor looked for them) and I have never damaged a lens because of the lack of a filter.

The coatings deposited on optical elements are surprinsingly sturdy and will tolerate a lot. They are not invincible but they are not "fragile". I would worry more about zoom creep or internal dust than damage to the front element.
11-20-2009, 01:47 PM   #18
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The discussion has now been changed to "to filter or not to filter."

This is like religion. I don't think it's gonna go anywhere.
11-20-2009, 01:54 PM   #19
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QuoteOriginally posted by glasbak Quote
I don't think it is wise to take advice from someone who obviously does not know much about optics.
Imperfect filters have more effect on long lenses !
Care to put any reasoning behind your insult? Because you are in fact wrong. The closer the virtual image of a lens is to the lens' hyperfocal distance, the more interference a filter may possibly have on the lens. The longer lens is, the smaller of an aperture it takes to get close to hyperfocal distance; as in, an aperture that no one would use, and most telephoto lenses wouldn't even be able to stop down to.

11-20-2009, 02:03 PM   #20
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QuoteOriginally posted by pxpaulx Quote
I kissed the 'protective' filters goodbye after some night time shots with massive glare (such as were shown above). If you can't tell that is flare from a filter, well, I have no response to that, honestly!
So you're basically saying it is just as likely to be the lens flaring up and not the filter, because you're not able to give any information either way ("I have no response to that!").
11-20-2009, 02:17 PM   #21
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QuoteOriginally posted by wallyb Quote
Care to put any reasoning behind your insult? Because you are in fact wrong. The closer the virtual image of a lens is to the lens' hyperfocal distance, the more interference a filter may possibly have on the lens. The longer lens is, the smaller of an aperture it takes to get close to hyperfocal distance; as in, an aperture that no one would use, and most telephoto lenses wouldn't even be able to stop down to.
Ok,
for sake of argument, lets say the imperfect filter is a one diopter closeup lens.
Put it before a 1000mm lens, and it will half the focal distance.
Put it on a 100mm lens, and it will shorten it about 10%.
Imperfect filters usually have some wavy and/or wedge shape. But the same imperfection will have more effect when it is farther away from the sensor.
11-20-2009, 02:20 PM   #22
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QuoteOriginally posted by wallyb Quote
So you're basically saying it is just as likely to be the lens flaring up and not the filter, because you're not able to give any information either way ("I have no response to that!").
Only thing I might add is I stopped using filters of any kind on my moon shots. Found it created a ghost effect with it on. Soon as I took off the filter it was gone. And I am a guy who had a filter on all my lenses ever since my first K1000 back in the late 70's. I still keep them on some lenses but not all. If someone asked me now though I'd tell them to keep a hood on while shooting and a cap on when not shooting. That's the best protection.
11-20-2009, 02:23 PM   #23
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I bought a cheap UV filter for my Canon 50mm f/1.8 II when I got my first DSLR a year ago. I threw it on and used it like that for the first 6 months or so, when I realized that it was flaring way more than what I thought was appropriate.

Flipping the filter off, I did a test back/forth and there was definitely a drop in sharpness/resolution, a hard rise in green fringing and much worse at flare resistance with the filter.

I stopped using filters as soon as I tried this (not that I did much before, that is), but I'll still throw a CPL on there when I need to kill reflection off pavement or sky or whatever.

11-20-2009, 02:28 PM   #24
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QuoteOriginally posted by glasbak Quote
Ok,
for sake of argument, lets say the imperfect filter is a one diopter closeup lens.
Put it before a 1000mm lens, and it will half the focal distance.
Put it on a 100mm lens, and it will shorten it about 10%.
Imperfect filters usually have some wavy and/or wedge shape. But the same imperfection will have more effect when it is farther away from the sensor.
I fail to see any relevant argument in anything you just typed. First, this discussion is about UV filters and the image quality impact they make have on lenses, which is very little and even less for a longer lens. Second, of course a curved, magnifying element will have some kind of effect on the output image of a lens, that is its purpose. Again this is just about plain UV filters. Third, the possibility of any imperfections of a filter showing up is not directly related to the filter's distance from the focal plane, but is a combination of factors including the closeness of the virtual image to the hyperfocal distance, and the distance from the front element to the filter (which is usually negligible).
11-20-2009, 02:30 PM   #25
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QuoteOriginally posted by graphicgr8s Quote
Only thing I might add is I stopped using filters of any kind on my moon shots. Found it created a ghost effect with it on. Soon as I took off the filter it was gone. And I am a guy who had a filter on all my lenses ever since my first K1000 back in the late 70's. I still keep them on some lenses but not all. If someone asked me now though I'd tell them to keep a hood on while shooting and a cap on when not shooting. That's the best protection.
It is certain that in extremely high-contrast situations like that, there may be additional flare induced from a filter. That is the 5% I alluded to earlier, which most people are not likely to encounter and belong to a very specific type of photography.
11-20-2009, 02:31 PM   #26
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QuoteOriginally posted by Fixcinater Quote
I bought a cheap UV filter for my Canon 50mm f/1.8 II when I got my first DSLR a year ago. I threw it on and used it like that for the first 6 months or so, when I realized that it was flaring way more than what I thought was appropriate.

Flipping the filter off, I did a test back/forth and there was definitely a drop in sharpness/resolution, a hard rise in green fringing and much worse at flare resistance with the filter.

I stopped using filters as soon as I tried this (not that I did much before, that is), but I'll still throw a CPL on there when I need to kill reflection off pavement or sky or whatever.
Was it a multicoated glass UV filter like I recommended? And if it was, do you have any sample images to prove your claims? If it wasn't, I don't see how it could be relevant to earlier posts in this thread. I could say I put a garbage bag over my lens and was unhappy with the resulting image quality, but that doesn't have any relevance to this conversation either.
11-20-2009, 02:45 PM   #27
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QuoteOriginally posted by wallyb Quote
Second, of course a curved, magnifying element will have some kind of effect on the output image of a lens, that is its purpose. Again this is just about plain UV filters.
Spot the cheap plain UV filter, its obviously curved in several ways, and although it won't act as a magnifying element, but surely will damage image quality.

11-20-2009, 02:51 PM   #28
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QuoteOriginally posted by glasbak Quote
Spot the cheap plain UV filter, its obviously curved in several ways, and although it won't act as a magnifying element, but surely will damage image quality.
It's hard to tell in that image, and it will not "surely damage image quality". You also fail to say if "cheap" means multicoated and glass, as I stated before. You are comparing incidental images of a light reflected off the filter. This has no relation to how the light coming into a lens with a filter attached will act. You are plain wrong, and the lack of any scientific reasoning in your "test" amplifies that.
11-20-2009, 03:39 PM   #29
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L'il bitty shower caps!

You wanna protect a lens from contamination in the field? You recall those little plastic covers that look like shower caps for squirrels that your momma used to use to cover leftovers in the reefer?

They store in your pocket when you're shooting and I've never lost one ('cause they're so cheap, I suppose).

And as a side benefit, when I was tempted to photograph an ill-tempered child slipping one on each ear provided enough distraction that I escaped unharmed.

However, most of my user lenses DO sport filter RINGS. Some are labeled UV, some red, some purple with polka dots. Makes no difference 'cause there's NO glass in those rings! They come from the cheapest filters I can find and never cause optical problems. What they do is provide a 2-4mm shade/hood that takes all the dents and dings that otherwise effect the lens threads.

Serious protection comes from real lens caps.

Filter effects come from quality filters as needed.

H2
11-20-2009, 04:27 PM   #30
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QuoteOriginally posted by wallyb Quote
Kirivon, to truly tell whether it's the filter's fault, you would have to do comparison shots. So, until those are done, there's no reason to believe it's not just the lens flaring up.
Good comparison to see effects of various UV filters.. well best I found so far..

UV filters test - Introduction - Lenstip.com
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