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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

214 Responses to “Good Times with Bad Filters”

Henry Posner said:

"have you ever seen an example of a filter preventing damage to a lens?"

I shot a food fight in a college frat house dining room once. Terrific mess but the filter saved me having to send an expensive lens through a washing machine and let me complete the rest of the day's assignment.

I've also shot football, rugby, soccer, rodeos where being able to give a filter a good swipe also met me finish the gig.

--
Henry Posner
B&H Photo-Video

tigrebleu74 said:

Well, UV filters on digital cameras aren't very useful anymore in the first place. There is already an excellent UV filter on the sensor of most digital cameras.

So unless you plan to do a shooting at high altitudes, were UV radiation is stronger, a simple, clear protection filter will do a fine job at... protecting your lens!

Of course, a good quality protection filter will still be better than a low quality protection filter...

Sky_walker said:

Well, i use filters for lens protection and I think it works very well for me. I have one (kit) lens, that I an my family members occasionally use, it has never seen any filter and right now you can clearly see how the coating is damaged on the front element - both cracks and holes can be found.

So all my other, more expensive lenses use filters.

It's a great protection against fingers, people trying to wipe-out dust or fingerprints, sand, water, etc. IF you use your lenses alone - than feel free to skip the UVs. But if you plan to borrow your lenses to people around - I strongly recommend getting a filter.

James Kelley said:

Did you try the bumper sticker shot with one of the best and then one of the worst - a bit more real world don'tcha think?
No names of manufacturers necessary but an interesting test.

Eric said:

did anyone notice the stack of "cheap" filters is way out of focus? that might have something to do with the quality issue. the b & w stack is sharp. could this be called "stacking" the deck?

Eric said:

I had an 80-200 roll off a desk in high school and ruin a perfectly good filter. It cracked and bent, but the lens threads were fine.
So it does happen. That was almost 30 years ago, though, so it doesn't happen often...

GregL said:

I often use several filters, particularly for b&w film pics (orange, NDGrad, polariser). Some of my filters are cheapos; that 5 filter test has me feeling circumspect about even 2 filters (ie. typically NDGrad and polariser). I think I'm going to have to do a bit of testing.

Mike said:

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....

LensRentals Employee

Roger Cicala said:

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.

John said:

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 said:

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...

Ashley Pomeroy said:

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.

Marty4650 said:

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

Someone would buy it.

Marc said:

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

JeffT said:

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 said:

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...

Lee Duguid said:

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

Daf said:

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 said:

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 said:

Idiotic

Zoltan said:

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.

@ID7 said:

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

Bob B. said:

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 said:

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 said:

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 said:

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

Rob said:

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.

Jes said:

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 said:

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 said:

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.

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