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01-02-2012, 01:22 PM   #16
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QuoteOriginally posted by reivax Quote
Does every filter degrade the IQ? I have a B&W Haze filter on my 50 1.4 (came with the lens and decided to leave it on). I also have a UV filter on my 55-300 (can't remember the brand right now). I've always wondered if I should leave them on, or take them off.

I know a lot of people are completely against using filters. I don't really use those filters for the effect, I leave them on to protect the lens. Is this really necessary?
It will degrade the IQ no matter how good the filter is, the question is if it's noticable and most often with a good filter there are little problems.

I'm not against using filters but i don't believe a filter will protect the lens if you bump into somthing or if a stone gets throw to it.
The filter is very thing glass so it will shatter and those sharp shatters will probably scratch the coating.
Modern lenses use protective coatings and the front elements are quite thick and often curved so they can take some force, at least a lot more than the filter.
Using filter to protect it from mud, salt and sandstorm would be a good idea but how often will you normaly shoot in such condition?

Also you pay a lot of money for a lens and what do you do... put extra glass infront of it, just doesn't make much sense to me.

This discusion is done to dead though... just search the forum if you want to read more.

01-02-2012, 01:25 PM   #17
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QuoteOriginally posted by dms Quote
Re-looking at your first two images--it does look like all planes are better IQ--so although my comment about refocusing is still theoretically sound, and possibly an improvement, it does appear the filter caused some loss of sharpness. But try it again with refocusing (maybe even vary the focus point slightly over several shots) before spending $. Ultimately If a better filter is required I would think you are looking at a few hundred dollars--at which point the extra protection may not cost effective.
I've read that the more elements a lens have the worst the effect of a filter will be, not sure why it was... internal reflections maybe?


Just get an insurance if you want extra protection
01-02-2012, 01:33 PM   #18
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QuoteOriginally posted by dms Quote
The greater the lens focal length the greater the focus shift with a filter of non-zero thickness. This can be offset by refocusing with the filter in place--try this before deciding it is other degradation due to filter. (BTW this is one reason the Wratten (kodak, now I believe Tiffen) gels were (are) used--they are thin.
QuoteOriginally posted by dms Quote
As regards hoods--on second thought-I guess the glass filter being broken--absorbs some shock--so if the lens smacks a rock/pavement head on the glass filter will be much better.

Why not try and see if the shift problem is there--and if not then try another approach. Maybe by a high quality used filter (can be any type) and see if it works--a filter type not used for digital and thus low $ now (or borrow from a friend)--if it works (no degradation) then invest in the particular filter you require.
QuoteOriginally posted by dms Quote
Re-looking at your first two images--it does look like all planes are better IQ--so although my comment about refocusing is still theoretically sound, and possibly an improvement, it does appear the filter caused some loss of sharpness. But try it again with refocusing (maybe even vary the focus point slightly over several shots) before spending $. Ultimately If a better filter is required I would think you are looking at a few hundred dollars--at which point the extra protection may not cost effective.
@dms, just to clarify, was your suggestion to refocus based on thinking I was not refocusing. I was refocusing when changing filter (on or off) because of the physical handling on the lens, but tried to be consistant and all other setting the same. I also did some paving bricks (a few times) where the focus point was shifted, but easy to spot, and similar results.

01-02-2012, 01:36 PM - 1 Like   #19
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Anything in front of a lens will cause a degradation in image quality. It may be small and negligible or in can be profound. Some filters provide benefits that counteract the IQ loss. For example a polarizer will provide better contrast, clarity and color saturation which in most cases are more important that a little overall loss in sharpness and color shift. An ND filter will make it possible to shoot in situations that otherwise you would not be able, so it is either that on nothing.

A UV/Skylight filter on the other hand, provides no benefits to a digital sensor (Skylights have a warm cast but that can be adjusted in finer steps using WB corrections in PP). Some will argue that they provide protection to the lens, but a hood and lens cap will provide better protection. The hood will improve the contrast also, so it has additional benefits. If the conditions are very hostile (e.g. on a windy beach environment, or in a sandstorm) then by all means a protective filter must be used along with other measures to protect the camera and your eyes. And if you use them in a night scene with bright light sources, you'll get a lot of flares and ghosts.

If the lens is that precious and needs protection, then one should consider getting insurance.

01-02-2012, 01:39 PM   #20
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QuoteOriginally posted by Anvh Quote
Some lenses really hate filters, don't know if the Sigma is one of them but might well be.
Don't know if anyone does use this lens with filter without a problem?
QuoteOriginally posted by Anvh Quote
It will degrade the IQ no matter how good the filter is, the question is if it's noticable and most often with a good filter there are little problems.

I'm not against using filters but i don't believe a filter will protect the lens if you bump into somthing or if a stone gets throw to it.
The filter is very thing glass so it will shatter and those sharp shatters will probably scratch the coating.
Modern lenses use protective coatings and the front elements are quite thick and often curved so they can take some force, at least a lot more than the filter.
Using filter to protect it from mud, salt and sandstorm would be a good idea but how often will you normaly shoot in such condition?

Also you pay a lot of money for a lens and what do you do... put extra glass infront of it, just doesn't make much sense to me.

This discusion is done to dead though... just search the forum if you want to read more.
QuoteOriginally posted by Anvh Quote
I've read that the more elements a lens have the worst the effect of a filter will be, not sure why it was... internal reflections maybe?


Just get an insurance if you want extra protection
@Anvh, some thought provoking comments. Will need to read up some more.
01-02-2012, 01:45 PM   #21
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The entire UV filter protects vs. No it degrades and a hood is better debate is one that I specifically avoided in my response because its been done to death AND its like arguing religion.

It's my firm belief that IF you decide to place a UV filter in front of your lens then knowing how good it is, what its impact is on the light streaming into the lens, etc. is important if you take your photography seriously at all.
01-02-2012, 02:15 PM   #22
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QuoteOriginally posted by Docrwm Quote
The entire UV filter protects vs. No it degrades and a hood is better debate is one that I specifically avoided in my response because its been done to death AND its like arguing religion.

It's my firm belief that IF you decide to place a UV filter in front of your lens then knowing how good it is, what its impact is on the light streaming into the lens, etc. is important if you take your photography seriously at all.
Noted! Need to do some research.
01-02-2012, 02:35 PM   #23
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QuoteOriginally posted by KevinR Quote
@Anvh, some thought provoking comments. Will need to read up some more.
will try to look up about the element thing and also will try to find about the refocus issue.
I'm quite curious about that myself.

And really don't be worried about damaging your lens, look up on youtube a clip named Canon Glass, someone is abusing his broken 50mm there to see what it can take.
I'm quite sure most filters will be broken half way through that "test"

01-02-2012, 03:02 PM   #24
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Kevin, yes my initial thinking was perhaps you did not refocus, however, as you did, it would seem that effect is accounted for. The effect on IQ at the 500 mm end does seem quite significant--interesting you did it. If you see improvement with another filter will be nice to hear about it. Also I wonder if the filter testing is the whole story--perhaps one needs to do your kind of test to assess filter(s) at very large focal lengths.
01-03-2012, 02:45 AM   #25
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What I'd like to do some time, is compare the IQ degradation at different focal lengths and also image distances. I had read much about the 170-500 being soft at the 500mm end, so just assumed the results were "normal", and hence just used to compensate by not going much beyond 400-425mm if I was concerned about IQ and got much better results there.

Definitely getting better images now without the filter, particularly of bird feather detail; but then a lot of other aspects have changed with the K-5 high ISO allowing for stopping down the apeture without missing the shot.

Thanks for all the ideas and comments so far.
01-04-2012, 01:10 AM   #26
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I think you've got hold of a rogue filter there. You may find these links interesting:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/124056-impact-...uv-filter.html

Experimenting with Stacks of UV Filters

I think the conclusion is that a really high quality filter won't have any visible effect, but a cheap filter is very likely going to degrade the image. The other thing to look out for with a UV protection filter is of course flare resistance. Decent multicoating is a must, but you'll no doubt be getting this if you're buying a good quality filter. Even so, there are situations where you might remove the filter in order to prevent the possibility of flare - specifically night scenes with bright lights.

Anyway, it would seem that you won't go far wrong with the multicoated offerings from the likes of Hoya, Marumi and B&W.
01-04-2012, 05:04 AM   #27
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QuoteOriginally posted by Docrwm Quote
There has been some discussion on eBay of counterfeit Kenko UV Japan filters being sold. They're lower cost filters to begin with but still people copy and counterfeit.

...

For example, Hoya has lenses at the top and bottom but has 3 models at the top:
Hoya 72 mm HMC
Hoya 72 mm Pro1 Digital MC
Hoya 72 mm HMC Super
...
1. Kenko filters ARE Hoya filters. Kenko is only the brand name for the Hoya home market (Japan) and should not be sold internationally. So, whether you buy a Hoya or Kenko HMC/HMC Super/Pro1 etc. does not make any difference.

2. a counterfeited filter is a real possibility.

We had loads of filter discussions over the last two years or so, which contain valuable information, for instance: https://www.pentaxforums.com/forums/pentax-dslr-discussion/134270-filter-quality.html and https://www.pentaxforums.com/forums/photographic-technique/104136-need-advice-types-filter.html for a start.

Ben
02-27-2012, 03:39 AM   #28
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QuoteOriginally posted by KevinR Quote
I've tended to be a UV filter addict from the old school of protect the lens thought. But was playing with my Sigma 170-500 on the new K-5 a bit over a month ago, and while doodling thought of comparing images with and without the UV filter.

I tried to keep things the same as best possible, although focus points might not be perfectly the same, and the results seem to show an appreciate IQ degradation with the filter on. I did a few repeats on roof tiles and paving bricks with similar results

I've got basically the exact same results using my Sigma 135-400mm, I'm really quite pleased to have discovered it was the filter because it was driving me mad (I knew i'd had much sharper shots from the same lens in the past) Filter that was on mine is a Marumi 77mm MC-UV III

Both F6.3 1/2000th sec top without filter, obviously (and yes I do spy that bit of dust on the sensor )

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02-27-2012, 04:12 AM   #29
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I used to be the same, putting UV filters on ALL my precious lenses to protect them. But when I noticed some degradation in IQ, that all changed very quickly. Suddenly I thought to myself: "Why buy state-of-the-art computer-designed lenses with renowed SMC coatings and then have that lens shoot through a piece of glass of a few dollars?"

Now I use a filter on my one-and-only WR lens. But only when it rains, just to avoid having to clean the glass.

Ok, I'm a bit paranoid about sharpness. Any IQ degradation, if I can see it or not, is to much. (I was so thrilled to find out camera's without AA filter are so much sharper, and so bummed when I found out it was impossible to have it removed from the K5.)

Last edited by Clavius; 02-27-2012 at 04:24 AM.
02-28-2012, 06:25 AM   #30
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After reading this thread yesterday, I decided to test all of my lenses to see what kind of difference the UV filter had on IQ. I chose a shingled roof of a low shed, and a sign with white lettering as the subject of the test. The shingles for contrast & detail, and the sign for CA. All shots were taken at f8/ISO200 on a sunny day. I focused carefully, took the shot with the filter, removed the filter, refocused and took the same shot from the same spot. In the case of my zooms, I shot at the widest focal length, in the middle of the range, then at the long end to check the entire range. Lens hood was used in all cases & the camera was a K-x.

I was surprised to find very little difference (if any) in the majority of the shots when viewed at full resolution at the point of focus. There were a couple of exceptions: The Tair 500mm mirror lens was decidedly better without the UV filter, and most surprisingly, the Tamron 60-300 (model 23a) was actually a little better with the filter. (I know! I was blown away by that result as well. I may repeat that test, since that makes no sense, unless the filter is actually doing it's job in the UV department, which is doubtful.)

I fully expected definite IQ degradation with the filters present. What makes it even more of a shock, is the filters are with one exception, cheap Massa, Zeikos, & Prinz filters.

Weird, huh?

Cheers,
Bobbo :-)
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