3 stacked optical filters don't seem to affect IQ

[slackercruster]

I read on one of the forums where someone said they don't like to use UV filters cause they degrade the image with a layer of glass over the lens. While I'm not in the position to argue against that with lab conditions. I will say using 3 filters of glass over my lens did not seem to hurt IQ one bit.

Some background info...

I did not set out to do this test. Nor did I set out to shot the image with 3 filters on it. I was shooting some landscapes in the cemetery. I had a UV filter on, as I have on almost all my lenses. I also added a polarizer consisting of 2 glass filters. The polarizer was even dusty since I forgot to bring a blower with me. So 3 pieces of glass were in front of a 35mmA 645 lens. When it came time to shoot the gravestone I had forgot that I had the polarizer on it or would have removed it.

Let me apologize to those that are offended by religious symbols. I'm not religious myself. (Well I may be 'religious' about shooting in the cemetery!) So I did not pick the subject matter to do this test on. It caught my eye as an interesting grave stone with the weathering. And only after I saw the results and remembered the 3 filters did I decided to do a writeup on it. And to those of you who are devout in your beliefs...well you get a bonus with the filter test!

Pentax 645D, Pentax 645 35mmA lens. Top image has been cropped about 15-20% Hand held, no mirror lockup, no tripod. RAW image was processed as a 0,-1,+1 HDR with 3 images created from 1 RAW file.

The resulting TIFF is much sharper than these reduced JPEGs. But, you can still see the sharpness with 3 filters.
Now it may be sharper with no filters. I never shot it wihtout at least 1. But the point here is 3 filters and it is still doable very nicely.

 

[Robin Usagani]

the photos have broken link.


I had a 2nd shooter used an UV filter, I saw several photos had little red orbs. It didnt even have sunglare, it was just shooting something a little bright. Frustrating. Ill post the photos when i get a chance.

 

[Overread]

Eh its a test that shows nothing however. You can't see if the filters have an effect or not unless you present photos taken under identical conditions both with and without the filters being present. For a filter test you'd also want some spot light sources in the scene to test the effect of the additional glass upon any artifact generation.


Then you can show what the photos look like both with and without the filters being present. That gives you a base answer to how much or how little effect that the filters are having upon the end photo. Results should also be presented with minimal to no editing barring base output processing to get a visible photo.


After that you can then present edited photos at suitable and normal output sizes; you could even visally compared output prints as well. That gives you not only a baseline showing the difference, but also shows you the "Real" world effect of having the filters on the camera.




Also remember that most of the "don't use a UV filter" advice is given quickly because people who buy filters early on are often buying very cheap ones which can have a very detrimental effect on image quality (heck really bad ones can even mess up the AF accuracy). They simply don't see why their £100-200 lens needs a filter of £60-100 in price to fit on the front just for "protection" (esp when objective viewing shows that filters offer limited to no actual protection outside of specific situations.

 

[Derrel]

Who was it that used to say, "Well...there you go!" Can't recollect who it was, but, well...there you go!

Anyway...Pentax 645D...hmmmm...now THAT rig sounds nice!

 

[bratkinson]

Perhaps 3 high-quality filters have negligible IQ degradation to the average eye. But even so, there -is- some, however minor. And, as well known, cheapo filters only cause lots of flares, 'star-effect', haze, and whatever else.

And for those that haven't seen this one yet:LensRentals.com - Good Times with Bad Filters

 

[Solarflare]

[...] You can't see if the filters have an effect or not unless you present photos taken under identical conditions both with and without the filters being present. [...]

+1

And high quality filters should "only" mess up the colors and contrast, not cause any unsharpness or distortion. Thats the domain of cheap plastic filters with no coating etc.

Mind, lenses are also glass. So filters only add to the problems the lens glass already has.

 

[slackercruster]

On another forum a couple of guys said my pix here look like PS stuff and were very poor.

You get all types on the forums. But I don't care. I always like to check into complaints. So I looked at the size reduction from my originals to what ended up here to see if the scoffers have any credibility.

The RAW was about 55mb. I uploaded about 900kb jpeg to photobucket. What came out at the forum was a little over 300kb

What is that? About 1/2 of 1% is left from the original? Plus JPEG destruction? I think it is still fantastic res for a 99.5% loss from the original.

And it is good to have pixel peepers like these guys. I never noticed the spider webs under the cross one peeper mentioned. Too focused on the interesting patina of the metal. The spider webs could have come out better on a tripod and a small aperture. But anyone can see the DOF is very shallow.

Anyway, let me know how to post the hi res TIFF if you want to see em guys. (gals)

 

[slackercruster]

[...] You can't see if the filters have an effect or not unless you present photos taken under identical conditions both with and without the filters being present. [...]

+1

And high quality filters should "only" mess up the colors and contrast, not cause any unsharpness or distortion. Thats the domain of cheap plastic filters with no coating etc.

Mind, lenses are also glass. So filters only add to the problems the lens glass already has.

Yes no doubt. Less stuff up front the better.

I only shot with 3 filter by mistake. But I always like to keep a UV for protection if possible

 

[Derrel]

Yeah...there's ample resolving power being demonstrated for JPEG shots in the 300k size class. I've recently been looking into the method you mentioned using , "RAW image was processed as a 0,-1,+1 HDR ". I think I might start using that type of approach on some landscape images I've started doing recently. Thanks for posting.

 

[480sparky]

...........Anyway, let me know how to post the hi res TIFF if you want to see em guys. (gals)

Put all the images you want to use for comparison into a zipped file. Upload that zip file to any one of the thousands of free file hosting web sites out there. Then post a link to it.

 

[amolitor]

More stuff is going to degrade the image, period. They haven't invented a sharpening filter yet (thank god).

The point is whether it degrades it enough to matter.

We're obsessed with sharpness and reducing flare and all that business, these days. It is true that you can always add, but can never subtract, softness, glare, and flare in post, but the obsession is still a bit much. Did the image satisfy you, with three filters on? Fantastic. Does it satisfy me, with 3 filters on? No, but that has nothing to do with the filters.

 

[Garbz]

It all depends on what filter and to what extent. I own a 36megapixel camera and I haven't found any sharpness issues as a result of any UV filters I own. I did however have a Hoya HMC filter on my D200 that was horrendous and was quickly sent to the bin.

Now reflection and ghosting on the other hand will definitely affect your image regardless of how much money you spend on the ideal filter. Until they invent a coating which doesn't create a gap in the refractive index of glass this can't be worked around. Take your triple stack and do some nighttime shots. Be prepared to be disappointed.