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Author Topic: UV filters and image quality  (Read 7165 times)
The Ute
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« on: September 20, 2012, 07:12:36 AM »
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I have high quality UV filters on all of my lenses.

All other things being equal do they detract at all from image quality ?

In other words, is it better not to be using one ?

TIA
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Graystar
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« Reply #1 on: September 20, 2012, 08:19:29 AM »
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In reference to image quality, you should never use a filter if you don't require the effects of that filter.

A filter may or may not detract from the image quality.  It all depends on the lighting conditions.  You're most likely to have IQ issues in bright conditions, and when photographing light sources...such as neon lights.  In these cases, reflections start to become an issue.  You'll get flare, mirrored points of light, and even ghost images of bright subjects.  UV and clear protective filters are most susceptible to these kinds of IQ problems because they're they let through nearly all the light of the scene.  A polarizer or one-stop ND filter only lets through half the light of the scene, and so will suffer less from such artifacts.

With modern digital cameras, you don't need UV filters as there's already a UV filter in front of the sensor.  To protect the lens, use a lens hood.  The lens hood will provide additional protection against flare as well.  Use a clear protective filter when there are environmental issues such as salt from sea spray or sulfur from Yellowstone geysers.
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The Ute
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« Reply #2 on: September 20, 2012, 08:34:59 AM »
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Thanks for the reply.

I have heard it argued both ways.
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PDobson
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« Reply #3 on: September 21, 2012, 12:01:37 PM »
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Don't underestimate the protection that a lens hood gives you. I generally leave my lens cap off and rely on the hood. I've dragged my 17-40 F4L up so many climbs that the camera body and hood are just trashed. I have to tape the hood to keep it on. Even after all of that, the important part, the glass itself, is still flawless. Protection and improved image quality: the hood delivers.

Phillip
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joneil
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« Reply #4 on: September 23, 2012, 05:19:08 PM »
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Don't underestimate the protection that a lens hood gives you. I generally leave my lens cap off and rely on the hood. I've dragged my 17-40 F4L up so many climbs that the camera body and hood are just trashed. I have to tape the hood to keep it on. Even after all of that, the important part, the glass itself, is still flawless. Protection and improved image quality: the hood delivers.

Phillip

I agree completely.  I find a good heavy duty lens hood usually does more to protect my glass than anything else.

The one exception is in high wind,especially around snow or sand.  That's the one time I think a good uv filter is worth the money
Joe

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PDobson
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« Reply #5 on: September 24, 2012, 09:55:59 AM »
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Makes a lot of sense about the sand. It's potential abrasion that is hard to protect against. I don't worry about driving snow/rain/fog. I'm going to be shooting through snowflakes or droplets stuck to the front element no matter what I do. Fortunately it will just evaporate away after the storm.
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IanBrowne
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« Reply #6 on: October 04, 2012, 01:26:27 AM »
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 i live in a rather dusty part of the world and the UV filter is there to keep most the dust off the front element. I never use lens caps; i just lose than LO L

I have also "saved" a couple dropped lenses because the filter took most of the damage
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ErikKaffehr
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« Reply #7 on: October 04, 2012, 01:47:44 AM »
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Hi,

I much rather clean an UV filter than a front lens. I'd suggest that a filter with excellent multicoating affects the image little, but it will of course degrade some. Most lenses have quite a few free glass surfaces and adding a filter increases the number of those surfaces by two.

I would say, that in 99.9% of the cases you would see little difference.

Yes hoods are good protection, unless they shake loose.

Best regards
Erik




I have high quality UV filters on all of my lenses.

All other things being equal do they detract at all from image quality ?

In other words, is it better not to be using one ?

TIA
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Rand47
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« Reply #8 on: October 05, 2012, 10:52:01 AM »
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Check this out:   http://www.lensrentals.com/blog/2008/10/front-element-scratches

Unless a particular filter/lens combination causes a problem w/ flare or some other problem, (and there's always that possibility) I think the protection offered exceeds any nitpick theoretical image quality degradation. This discussion has been going on since God invented light and I've yet to see a side by side demonstration of two images made w/ a good quality lens, with, and without a good quality filter, where any difference in IQ is visible to human eyes.

I've tested all my Zeiss lenses with and without at 100% and in prints, and I have to carefully label which is which or I couldn't tell.  There has only been one situation w/ a very long (400mm) zoom lens where I decided to go filter-less due to very slight differences in IQ in one or two images out of about 50 test images in various conditions.  And even in that case, if the wind is kicking up dust, snow, grit, I'd slap the filter back on in a heartbeat.  

« Last Edit: October 05, 2012, 11:00:40 AM by Rand47 » Logged
Sheldon N
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« Reply #9 on: October 05, 2012, 10:58:28 AM »
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Here's a comparison test I did a few years ago when I was curious about whether a UV filter degraded image quality.

Canon 5D and 35L at f/5.6 on a tripod, mirror lockup, self timer, etc. Four identical images taken. One was with no filter, one was with a B+W MRC filter, one was with a Heliopan UV filter ($150 filter), and one was with an UGLY beat up used filter that I got for free at the local camera shop (Tiffen brand).  Here's the full frame image, and the four 100% crops. You tell me which is which... Smiley





Now I will say that there was a notable difference in flare performance when I introduced a bright light source into the frame. For sharpness though, it was pretty much irrelevant.
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The Ute
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« Reply #10 on: October 05, 2012, 11:38:55 AM »
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Thanks to all of you who were kind enough to respond and offer your take.

I'm gonna stick with one because I live in a sandy environment.

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Graystar
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« Reply #11 on: October 05, 2012, 01:20:18 PM »
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Four identical images taken. One was with no filter, one was with a B+W MRC filter, one was with a Heliopan UV filter ($150 filter), and one was with an UGLY beat up used filter that I got for free at the local camera shop (Tiffen brand).  Here's the full frame image, and the four 100% crops. You tell me which is which... Smiley

We can't because you didn't include the area that would have aberrations caused by the filter.

The following flickr user has a good example of the type of problems that filters cause...
http://www.flickr.com/groups/canon_50mm/discuss/72157603907741669/
Filter on...


filter off...


So you see...you should have included crops from the area that might have reflection aberrations from the lights in plant.

In sunny conditions, a UV filter may also cause ghost images around subjects that looks like an odd form of camera shake or out of focus blur.  Sometimes the effect is very small...making the image seem as if it's just not as sharp as it could have been (which, of course, then gets blamed on the AF system.)
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Sheldon N
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« Reply #12 on: October 05, 2012, 03:53:03 PM »
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We can't because you didn't include the area that would have aberrations caused by the filter.


You must not have read my last sentence.... this was a sharpness test not a flare test. I did a different flare test with a bright source in the image (not shown) that revealed more noticeable differences between the filters.
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Graystar
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« Reply #13 on: October 05, 2012, 05:00:28 PM »
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You must not have read my last sentence.... this was a sharpness test not a flare test. I did a different flare test with a bright source in the image (not shown) that revealed more noticeable differences between the filters.

I read it.  It sounded more like a personal observation...not a directive.  But it doesn't matter...the issue of reflections is the primary reason why UV filters are to be avoided, so a demonstration that they don't cause loss of sharpness doesn't amount to much, especially when, as I said, some reflections can manifest themselves as a loss of sharpness.
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