What UV Filters to Get

Indeed, this is truly a debate for the ages.

lol true, i think many years from now this will still be in full flight :P

Lester Wareham wrote in post #2017291
I do hear lots of people say filters degrade image quality but have never seen any evidence to that effect.

Here's some evidence.

I spent $80 on a multicoated Hoya UV filter for my trip to Africa last year (I spent 2 months there).

This was the first shot of my trip, using the Tamron 28-75 f/2.8, a lens that has exceptional image quality and is sharper than my 70-200 f/4L.

Keep in mind I was standing underneath a shaded awning, and the sun was out of view 90 degrees to the right. But there is a huge lime green flare in the upper right part of the image, and the image was softer than anything this lens has ever produced. As soon as I saw the photos that night I took the filter off, and the pictures were wonderful thereafter. In fact the bottom image is one I took with the same lens on that same trip directly into the sun, but with no UV filter -- and I had less flare than that other shot in which the sun was out of view.

I will never ever again use a UV filter -- under any conditions -- unless I'm shooting film at high altitude.

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Did you have the hood on?

Can you also be more specific than, "multicoated Hoya UV filter?" Was it a Pro? The Heliopan and B+W filters are both better than the Hoya and I believe have more coatings as well. There's nothing special about a "multicoated Hoya UV filter."

But nevertheless, you can see these kinds of artifacts in the viewfinder... If you notice it, you can always take the filter off. I shoot with filters on all my lenses, all the time. I rarely, rarely have the experience you pointed out - typically only if I'm shooting at/towards a bright point light source (within or at edge of viewfinder).

If I have some time, I'll do a comparison to throw into the mix as well.

Yes, it was the Pro, and I ALWAYS have the hood on (except when adjusting my circ pol).

Not that the hood mattered, I mean I was standing in the shade.

DrPablo wrote in post #2021530
Here's some evidence.

I spent $80 on a multicoated Hoya UV filter for my trip to Africa last year (I spent 2 months there).

This was the first shot of my trip, using the Tamron 28-75 f/2.8, a lens that has exceptional image quality and is sharper than my 70-200 f/4L.

Keep in mind I was standing underneath a shaded awning, and the sun was out of view 90 degrees to the right. But there is a huge lime green flare in the upper right part of the image, and the image was softer than anything this lens has ever produced. As soon as I saw the photos that night I took the filter off, and the pictures were wonderful thereafter. In fact the bottom image is one I took with the same lens on that same trip directly into the sun, but with no UV filter -- and I had less flare than that other shot in which the sun was out of view.

I will never ever again use a UV filter -- under any conditions -- unless I'm shooting film at high altitude.

.....

At least you have a good reason to worry about filters. This is interesting. Its just a shame you don't have a with and without filter shot to clinch it.

Now I must say I have only been able to get this effect with the sun's disk in frame let alone out of view. And in that case it was the lens flaring.

Can you for info let us know:
a) Were you using a lens hood?
b) Where you at the long end or shot end of the focal length and what fstop?
c) As the sun could not have been shinning directly on the filter even without a hood, if it was possible something out of shot was reflecting the sun?
d) Exactly what Hoya filter model it was?

What I have been able to get in a test setup is some flare like this but generally much more compact but only with two lenses with well recessed front elements.

Yes, again I was using a lens hood and I was standing in the shade on a roofed veranda in the back of a restaurant.

The specs of the shot were ISO 200, 1/200 at f/10, and 75mm

If you look closely at the flare there is a soft specular highlight in the lower part of it, but it really isn't in the right spot to have propagated that particular flare. At any rate, that's the only potential source that's in the picture.

The filter was the Hoya UV Pro-1.


I'd have done test shots if it had occurred to me at the time.

At any rate, I think we can all take for granted that flare will happen more often with any filter -- I mean you're adding two new reflective surfaces with an air interface, so there will always be more flare.

What would be instructive would be to look at 100% crops for sharpness, color, and contrast with and without filters.

Then you really don't have any concrete evidence that the filter was the cause, do you? You can't identify a light source for the flare and you don't have a comparison shot under the same conditions without the filter to tie it to the filter.

I'd be inclined to suspect a reflection off an adjoining window. Remember, the 28-75 Tamron's got a hood designed for FF and to not vignette at 28 mm. So if you were any longer than 28 mm FF the hood's not at its most effective. And that includes using it at 28 on an APS-C. And unless the front element on the Tamron's really recessed, that would have flared under the same conditions of oblique light.

Well, I have no problem with skepticism, and it's not a controlled experiment.

I only have, as we say in medicine, 'historical controls'. I have never had flare or softness like that since removing the filter, and I never had it before.

But again, I was completely 100% in the shade, as was my lens. The roof over my head was a pretty effective lens hood itself. The rear facade of the restaurant was to my right, and its whole facade was in the shade as well. So there wasn't any bright light hitting the lens from an oblique angle other than what was in or near the frame.

But it's a moot point, because the flare happened, and whatever the source it spoiled an otherwise nice shot. And the flare was out of proportion to what I'd expect in those shooting conditions.

DrPablo wrote in post #2021651
Yes, again I was using a lens hood and I was standing in the shade on a roofed veranda in the back of a restaurant.

The specs of the shot were ISO 200, 1/200 at f/10, and 75mm

If you look closely at the flare there is a soft specular highlight in the lower part of it, but it really isn't in the right spot to have propagated that particular flare. At any rate, that's the only potential source that's in the picture.

The filter was the Hoya UV Pro-1.


I'd have done test shots if it had occurred to me at the time.

At any rate, I think we can all take for granted that flare will happen more often with any filter -- I mean you're adding two new reflective surfaces with an air interface, so there will always be more flare.

What would be instructive would be to look at 100% crops for sharpness, color, and contrast with and without filters.

I have done this using ISO measurements of MTF (SFR), the filters have no effect.

Also have done lots of flare tests with and without under controlled conditions making frame difference checks possible, thus my comments earlier. No sign of general lowering of contrast and in general lenses flare before the filter with the exception of two cases mentioned.

I ment to ask if your lens had a well recessed front element. That makes problems with filters but only with a bright light source in the frame.

Jon wrote in post #2021678
Then you really don't have any concrete evidence that the filter was the cause, do you? You can't identify a light source for the flare and you don't have a comparison shot under the same conditions without the filter to tie it to the filter.

I'd be inclined to suspect a reflection off an adjoining window. Remember, the 28-75 Tamron's got a hood designed for FF and to not vignette at 28 mm. So if you were any longer than 28 mm FF the hood's not at its most effective. And that includes using it at 28 on an APS-C. And unless the front element on the Tamron's really recessed, that would have flared under the same conditions of oblique light.

These were my feelings also Jon.

The only way to be sure is comparitive shots under controlled conditions. This is hard to do in the real world where lighting can change from moment to moment and the sun moves in the sky. This is why I tried an inside setup for my tests.

There are some more formal tests out there on the net; I have them bookmarked at home.

But again in the absence of hard data we can probably agree on the following:

1. There is a balance between image degradation and lens protection

2. The lenscap is the ultimate in both lens protection and image degradation

3. Any added glass element will cause some light dispersion, and any added glass interface will potentiate flare

4. Whether this visibly changes lens performance probably varies with conditions, and certainly is subject to interpretation according to the needs and attention of the photographer

5. you can actually take a little piece of a post-it note, put it smack in the center of your lens, and you won't see it on your final image (I've done it, it actually works) -- this means that cleaning marks and minor scratches are very unlikely to affect image quality

6. a UV filter probably does protect against certain things, including salt spray, sand, and accidentally sticking your thumb on the lens

7. there is a calculus of whether the potential protection is worth the potential image degradation, and none of us are trying to make rhetorical arguments -- just to educate one another

Finally, I'd mention that I bought lenses with good image quality for a reason -- and there is a reason there isn't a red stripe around UV filters.

As to point 5; you'd have to run before-and-after tests for IQ and contrast to determine the effect of scratches, dings, or Post-It notes on the image quality. But then, that's what us filter-users have been saying all along - if you have to run detailed tests to see the effect, it's not worth worrying about when compared to the peace of mind they provide.

Jon wrote in post #2021832
As to point 5; you'd have to run before-and-after tests for IQ and contrast to determine the effect of scratches, dings, or Post-It notes on the image quality. But then, that's what us filter-users have been saying all along - if you have to run detailed tests to see the effect, it's not worth worrying about when compared to the peace of mind they provide.

i think you have pretty much summed it up Jon.

One thing I am sure about, no mater how much evidence there is either way, few will change their filter using habits. The debate has been running for at least 20 years that I know of and will probably go on for plenty of time yet.