LensRentals.com

Good Times with Bad Filters

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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

Lensrentals.com

June, 2011

  • Mike

    I use filters on my walk around lens to protect from kids sticky fingers, dust, spray, or whatever environmental things are around. I'm not disciplined about the lens cap.

    On the other hand I have dropped my D300 with Sigma 18-50 2.8 lens first four feet onto concrete. The lens hood was a great shock absorber. A small chip on the lens hood, slightly mis-threaded filter. I put a little pressure with a pipe wrench on the uv filter to pop it back strait. Other than the chip on the hood, all is good.

    I'd say the shock absorbing property of the lens hood was more the savior than anything.

    This is probably a case of better lucky than good....

  • Roger Cicala

    John,

    I'm sure they've prevented damage from blowing sand or sparks or perhaps even salt spray. Whether they can actually make a difference if a lens is dropped I doubt, but it would be rare - certainly it could happen, but somewhere between "not very often" and "very nearly never". FWIW my opinion is the math people often use is wrong: the filter doesn't protect the $1,500 lens, it protects the $150 front element. I just don't think it's cost effective.

  • http://2look.blogspot.com/ John

    Roger, in your vast experience of renting hundreds (thousands) or lenses thousands (millions?) of times, have you ever seen an example of a filter preventing damage to a lens?

    Thanks for a great post!

  • Carl

    The replies to this blog seem to have gotten out of hand last night. Apparently a bunch of people from Europe (or nightowls in the USA) think this is twitter or something...

  • http://women-and-dreams.blogspot.com/ Ashley Pomeroy

    This is great fun - I have a mental image of Count Von Count from Sesame Street putting all the filters together. "Von filter! Ha, ha ha! Two filters! Ha ha ha!", and so on for an hour and a half. The shot of the B+W 77mm filters is iconic, you should put that up as a big poster in your shop.

    "Now I have two formats and 9 lenses to cover" - I tend to buy a few large filters and a bunch of stepping rings, which is doubly handy because, with a full-frame camera, some of my lenses vignette a tiny bit if I use a matched filter. E.g. my Tamron 28-75mm vignettes with 67mm filters at 28mm, but not with a 77mm filter mounted with a stepping ring. Stepping rings are cheaper than filters.

  • http://marty4650.blogspot.com/ Marty4650

    Lensbaby should market this concept. A set of 50 cheap filters that are stacked for "creative photography"....

    Someone would buy it.

  • Marc

    No filters seems to have the best result. Is it possible to rent no filters?

  • JeffT

    I think you're making the inverse of the mistake that engineers made with the O-rings on the space shuttle - ignoring the effect of stacked tolerances.

    For example, if a "good" filter lets through 99.5% of the light with perfect fidelity and causes 1% distortion, stacking 5 of them will result in 0.995^5 = 97.5% of light getting through with about 2.5% distortion.

    Now if you look at a "cheap" filter that is only very slightly less "good", let's say 97.5% (2% more distortion than the "good" filter), stack 5 of them and the net effect is 0.975^5 = 88.1%... a very significant difference with 5, but a very insignificant difference with just one.

    In reality, the effects are more subjective, but the math is the same. Stacking filters magnifies the imperfections exponentially, not linearly, and so looking at the effects of multiple filters can be very misleading when you're trying to evaluate a single filter versus another single filter for price vs. performance.

  • Scott

    Just use a lens cap for "protection"...Or a lens hood....A lot cheaper than expensive filters which are not worth the ectra expense. As for protecting the lens, any drop can damage more than just the front element, get yourself a good insurance policy on your gear...

  • http://www.leeduguid.com.au Lee Duguid

    Great post, thankfully I've never been a fan of UV filters....now I have a reason to hate them :)

  • http://www.dafyddowen.com Daf

    Ha ha - fun test.

    I once read somewhere and now stick to it - Why spend hundreds if not thousands on an expensive Pro lens, and then stick a piece of crap filter in front of it....
    I now get the best I can within budget (but will shop around and try eBay)

  • Mr S. Tyru

    Guys - I've spotted the problem, it's not the 'add ons' to the right of that lens that are the problem, its the 'add-on' to the left of the lens

    (cue Nikon v Canon debate)

  • SN

    Idiotic

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  • Zoltan

    Anyone paying $80-$100+ for a filter is only kidding themselves and making filter makers very rich.
    I personally have used the Hoya HMC and Marumi MC filters and did not notice any IQ degrading with them at all. I could recommend them as good filters that are fairly priced.

    Yes avoid the ultra cheapie uncoated ones by all means, yes the Hoya green range is poor and a few others. But don't stand here and tell me b+w filters are worth the money because I've tried them they are not.

  • http://www.id7.co.uk @ID7

    I'm off out to buy 200 filters. Great article, thanks for erm.... doing it.... My project for the weekend!

  • Bob B.

    OK...OK...this was a REALLY fun read...plus...I decided to replace all of the $10 "T" brand filters on all of my lens last month with B&W MRC Brass Pro filters. Now I have two formats and 9 lenses to cover and that is a LOT of mulla for... in effect..ummm nothing! LOL. I ordered from Hong Kong for substantial savings...but it was still painful! I noticed an extreme quality difference all the way around when the filters arrived..the brass rings are solid and non-binding to the lens and it was more than obvious to me that the glass and the MRC coating were head above the "T" brand. Lens rental...THANKS FOR VALIDATING MY PHOTOGRAPHIC INSTINCTS!!!!!

  • Nik Caduzo

    I understand what was the point, but I do not believe that such exaggeration can achieve the real goal. I would like to see the same image but with only one (preferably good quality) UV filter.

  • Brainiac

    This test is great, but it does not give answer all questions.

    Please, repeat it and check the effect on image quality if you stack 50 lens caps.

  • Herman

    I always dreamt of owning a looooong lens...
    Now I know how to achieve it!

  • Rob

    I've used UV filters as lens protectors. Is there an alternative? I've never heard anything bad about UV for photos (wasn't it a film issue?). Can we get clear lens protectors? Minimal filtration?

    This test shows it's not an issue using cheap filters because the degradation isn't visible to the naked eye.

  • http://www.airphilexpresspromo.com Jes

    Ditto first comment from Dave – yet another great post … funny, interesting, informative, and funny – makes a good point in an easy to see manner … and methodology is solid.

  • Jimmy

    Hey, great blog! The idea of putting 50 filters on a lens might seem ridiculous, but then - hey - is there a better way to show that one has to invest in best filters possible if having them on the lens is what they want, and only best results count? Many thanks for the "test" :)

  • louis

    Hi if i was you i would give this Guinness so you can claim your medal from Guinness book of records just for the hell of it before someone steals your limelight. Its all fun lets not get serious.

  • http://blog.trafficshaper.com Bob-O-Rama

    Hi,

    I've made a couple videos showing that the cheap filters which claim to block UV don't block UV at all - it uses a UV light source and scathing sarcasm.

    http://www.youtube.com/bob0rama#p/u/3/U5DPVme8Ak8

    http://www.youtube.com/bob0rama#p/a/u/2/5MN1n0HPmXc

    -- Bob

  • Erik

    At a certain large NY camera store, the basic HOYA UV in 77mm size cost around $50 while the no-name is $23. So the generic advice "If it cost $22 in 77mm size, it’s a crappy filter” is not contradicted by the lenstip article.

  • Scott

    Fun and ridiculous yes, but still interesting. Intrapolate five filters down to one and it's easy to see that a single crappy filter must be having some negative effect on your images.

  • http://wunderwood.org/most_casual_observer/ Walter Underwood

    Use a lens hood instead. If you've ever dropped a lens with a filter on it, you already know that the shards of broken filter don't "protect" the lens. And fingerprints don't hurt a lens, you just clean them off.

    A lens hood can only improve a lens, a UV filter can only hurt it.

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  • Jon

    D'oh! I just noticed the blog post on lens cleaning. A prior entry in your search engine didn't produce any results.