Roger's Corner

Good Times with Bad Filters

Published June 1, 2011

OK. First and foremost this is a fun post. It is not episode 362 of “Should you put a UV filter on your lens”. Some people use them. Some don’t. There’s not enough bandwidth to ever end that argument.

But here at Lensrentals, we have a ton of filters. We have some really good, very expensive filters. We have some OK, middle of the road filters. And because some customers, uhm, happen to return a very cheap filter in place of the one they were sent, we’ve obtained some crappy filters. Brand names aren’t necessary. If it cost $22 in 77mm size, it’s a crappy filter.

Anyway, one of the techs has to clean all those filters, make sure the threads are OK, and test them out. Honestly nobody likes to do it, so it gets put off until we need some filters or there’s just nothing else to do. So the other day Kenny is cleaning filters and testing the threads by mounting them one in front of the other until he made a nice mountain of 50 UV filters.

50 UV filters, cleaned and neatly stacked.

Not being the kind of people to let well enough alone, we decided to mount them to a 5D Mk II and 300 f4 we had handy and take a few pictures.

The well protected lens.

And of course see if the filters affected image quality. See if you can tell which images was shot with the 50 UV filters, and which without:

Shot of the building across the parking lot without filters (above) and with 50 UV filters (below). The one with the filters is actually better than I expected.

Of course there’s a lot of vignetting and haloing on the full size image:

Compared to no filters

Roger, do you have anything constructive to say, or are you just wasting blog space again?

Yes, actually I do. Fifty filters stacked is pretty ridiculous. But in that stack of 50 filters, as I said, there are some very good ones and some very bad ones. Lets compare a stack of each, shall we?

First, I had Kenny put the worst filters on the top of the stack (all were nonbrand, or brands we know are cheap and bad) and take a picture of the stack at an angle. All were freshly cleaned and if you look straight through them reasonably clear. Like a filter should be. But if you stack them and try to take an angled picture through several layers of them, the results were ugly.

View through a half dozen cheap filters stacked on top of each other. Try counting the filter rings inside the stack.

Yes, I know they don’t look clean in the image, but every one of those filters was freshly cleaned, and checked under a light. And if you look straight through them they were pretty clear. Looking at an angle tends to show you the weaknesses of a filter much better than looking straight through it. And remember: most of the light rays coming into the lens are coming in at an angle, not heading directly to the sensor in a straight line.

Now lets compare the stack with the expensive, top of the line filters (B&W, Heliopan, etc.) stacked the same way.

Stack of expensive UV filters one atop the other.

Hmmm. I’m starting to think there might be a difference here. But the proof is in the pudding. Lets modify our original experiment to something only slightly ridiculous. Instead of shooting through 50 filters, lets take the shot through 5 top of the line filters and another through 5 bottom of the line filters.

Here’s a 100% crop of a bumper sticker across the parking lot shot first with no filter, second with 5 stacked high end UV filters, and then with 5 stacked low grade UV filters.

100% crops of a bumper sticker shot through no filters, 5 stacked good UV filters, and 5 stacked cheap UV filters.

Now stacking 5 filters doesn’t have a ton of real world implications. Most people rarely stack two. But it is a fun demonstration that there really is a difference between good filters and cheap filters.

The good filters do a remarkable job: 5 stacked filters means 10 air-glass interfaces before the light even gets to the lens. That there’s only a little bit of image quality loss through all those filters is pretty impressive. This crop is from the center of the image, there’s more degradation to the sides, but still, it’s an impressive performance. And certainly lends credit to the idea that a high quality, multicoated UV filter has little effect on image quality.

Five bad filters, though, is another thing entirely. I’m completely aware, for those of you who are going to feel the need to point out the obvious, that nobody shoots with 5 UV filters. And I understand that one cheap UV filter wouldn’t have nearly as bad an effect on image quality as 5 of them. But I don’t think you can disagree that the good (and expensive, I know) filters have much less effect on image quality than the cheap filters.

BTW – before anyone asks, I avoided name brands of cheaper filters for a reason: many filter manufacturers make both pretty good, and pretty bad filters. You can tell the difference by the price or by reading carefully about the number of coatings, etc. A Tihoya $29 “high quality” filter is not the same as a Tihoya $79 “Professional” filter. This wasn’t meant to be a filter review, just a fun demonstration of the obvious.

Roger Cicala

June, 2011

Author: Roger Cicala

I’m Roger and I am the founder of Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in Roger's Corner
  • Hugo Chikamori

    Now…can we try that with 50 crappy 3 stop ND filters. I’ll see you next year for the result. It may take a month for the shutter to finally click. ~evil laughter~

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  • CCycomachead

    Many people forget some of the other advantages of filters.

    Weather Sealing. Having a filter on not only protects the front element and the lens barrel / body if dropped, but also prevents dust moisture and other debris from entering the lens, especially if the front element moves.

    Yes, you can buy weather sealed lenses, like L series, but most L lenses aren’t fully sealed unless they have a filter, and yes the 24-70, 24-105, and the 16-35 all require filters to be sealed.

    As far as the cost: $100 on a filter should be about right for the price of a thousand + (or even less really!) dollar lens. That’s one small piece of glass compared to the whole lens (and is a hell of a lot easier to manufacture!) so it’s really spending an ‘appropriate’ amount.

    The filter as a lens cap idea is neat, but it all depends on how you use it. If I’m walking around and keep the lens cap on and do need to take a photo ‘instantly’ my lens cap is either off (and the lens is protected by the hood) or it takes me half a second to pull a cap off. If I’m rushing and I drop the cap or something is what $10 or less to replace? If I’m always taking a filter on and off I’d be worrying about the quality of that filter and that it’d be protected, because I still wouldn’t put a cheap filter on as a lens cap (because I’d be worrying about the images that got taken with the filter on). Also, I can tell through the VF if a lens cap is on, but not if a filter is.

    There are also some lenses, like my 50 f1.8, where buying a quality filter doesn’t matter. The cost of the lens doesn’t justify the price of the filter. (Also while that 50 is pretty darn sharp on it’s own, its own glass isn’t as nice as my 24-70 so I have a feeling that it would be more adversely affected by a filter. Though I could be wrong about this.)

    Finally, the more glass you have the more problems you are bound to run into. It’s physics, but that doesn’t mean that clear filters aren’t still useful.

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  • That’s great guys! Really appreciate it. I was actually coming to the site to look for filters for an upcoming project. As always, you’ve gone the extra mile to help us out! Thanks for posting.

  • BADigiFoto

    The comparison photos with the view through the cheap filters reminds me of the countless cheap commercials running after midnight on commercial TVs, addressed to mostly intellectually challenged shoppers who can be fooled with the least bit of effort that they actually need the crap sold to them and they are getting getting a promotional (just now, just for you, but wait, there’s more…) type of deals.
    If you truly are serious about making such comparisons, shouldn’t you guys pay a little more attention to the correct exposure of BOTH images? I’m asking this question because I would like to assume that you haven’t purposefully made the expensive filters look sharper and the cheap ones unsharp, poorly exposed.
    Those of you who are not sure what I’m talking about feel free to look at the black frame of the first filter – not just that you can’t see through the first one properly (incorrectly blamed here on the quality of filters), but you can’t even see the outside edge/frame of the filter either, which clearly can mean only one thing: the photo was poorly exposed.
    And as long as there are such clear “mistakes” (as again, I wouldn’t want to call them deliberate deceptions), the trustworthiness of the entire post can be seriously questioned…

  • John Kim

    Hey, great article. Makes me wanna chuck all my cheap filters.

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  • Well, it depends on how you plan to use them. Filters are great when you know how to use them and when to use them.


  • Carlos

    Rebelphoton has a good simplified explanation. The 5 stacked filters amplify the loss in picture sharpness to a point that our eyes can perceive the decrease in quality/sharpness of the pic. But if you compare two pics with only one filter of each kind, the results could be inconclusive to the naked eye, but yet measurable with the proper instruments.

  • RebelPhoton

    This was actually a great opportunity to explain how the MTF of an imaging system is a result of the multiplication of all of its elements. So you might not ordinarily notice the difference in quality loss between a filter that lets through 98% of the original resolution and another that lets through 92%. (I’m making these numbers up).
    But if you stack several similar filters those differences quickly add up:
    So there is a very noticeable difference between a 10% loss and a 35% loss. This makes it easier to measure the difference between different brands and models.

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  • Gary Edwards

    Good test. Valid approach to gain observability of the effect.

  • Piechie

    Love it Roger – I actually got the link to this form an Adobe Lightroom FB post!

    Glad things are going great for ya! We we going to go out shooting again?

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  • Ashley Groome

    I never cease to be perplexed, by seeing a person of good, common sense, spending a couple of grand on a decent body and possibly as much again on a decent lens – and then get all bent out of shape because they have to pay 80 or 90 dollars for a decent UV filter. Go figure.

  • Very interesting article, i have some friends that buy a 1500 dlls lens and then buy a 15 dlls filter, and they have the brilliant idea of stacking a UV, and a ND from the same cheap brand, and cry because they dont have sharp images.

  • Carl

    Tigrebleu74, yours is an example of why forum and blog response posts are less than useful at times. People tend to feel the need to weigh in on something, and then get it wrong. Then no one corrects them, and assumes their statement is fact. You state that “There is already an excellent UV filter on the sensor of most digital cameras.” Actually, the filter on the sensor is a HIGH PASS infrared filter (as opposed to a low pass UV). Cameras which have been “modified” for infrared use, have these filters removed. But there is no UV filter on a digital sensor. I’m surprised Roger didn’t correct you.

  • Carl

    John Stone, yours is some good advice. I would like to see some of your images.

  • In the two shots comparing a stack of expencive filters and a stack of cheap ones.
    On the stack of cheap ones, the first filter should at least look SHARP! it looks out of focus.

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  • I enjoyed the article! Thanks! Keep it coming.

    @photofaculty that’s a hilarious and superb idea •lol•

  • Harald

    Are you planning to rent the ‘stack’ of 50 filters for Soft Focus Potraiture just like David Hamilton 🙂

  • As well as the photographic results, could you try this with circular polarising filters and do a video of how you put them all on and then how you get them all off again ?

  • John M

    Great fun test, but one thing that no-one has mentioned is that a filter being further away from the front element than normal will change the effect it has on image quality.

    Now I’m just trying to work out whether that would be for the better or for the worse!

  • MLWadester

    Lolz, @Uncle Toopula. I enjoyed the blog post, thanks to DPReview for posting!

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