Naked or filtered ... which works better

[DonSchap]

I have performed this test with the CZ 135mm f/1.8 ... and found its autofocus deeply affected, close-up, on the wide aperture. Using Manual Focus, the UV-filter had no effect. I was able to achieve a sharp, accurate center-of-focus (or spot-focus) on my subject.

The autofocus center-of-focus (f/2.5) shifted 1-3mm further back, directly caused by the addition of a relatively decent UV-filter. That can be a tremendous mis-focus, when you are going for sharpness and especially with a lens you paid over a grand for. Like I previously mentioned, manually focused, with the UV-filter on, I was able to get a sharp focus at the COF. Immediately switching back to AF ... it drifted back off to the 3mm displacement.


Solution: Obviously, shoot NAKED! Yep, remove the filter when you are ready to shoot with AF ... and your focus should be right on the mark. Mine has shifted to precisely where it should be.

The reason for this test was because it was suggested to me that I should try using my CZ 135mm f/1.8 in my remote bird shots. Well, as you can imagine, protecting the lens from damage is an important aspect of such an effort. The animals certainly have no respect for the costs involved :rolleyes: and having squirrels crawling all over the equipment is to be expected. The weather, too, plays a major role, as we are having rain and wind storms every other day. Using a UV-filter in a prophylactic role seems only prudent ... but, it is screwing up the focus to such a degree, the 135mm is not performing any better than 70-300mm f/4-5.6 on a bad day. I would have gained nothing by risking it.

But, as risky as it is, the reality of it is far worse. If I want to enjoy the power of this lens ... to hell with the filters. :o

Just thought I'd share, just in case you wonder what happens shooting through UV-filters. I have personally found that lower-end lenses seem to be more tolerant of the UV-filters. The cheaper the lens, the cheaper the UV can be. Or ... the more expensive the lens ... the less protection you can provide it. Although, there is a limit to that, also. It is like having an extremely sharp scalpel ... it does not take much to dull its edge. If it is a butter-knife, who cares?

Many will argue that putting a $50 filter on a $75 lens is silly. I would tend to agree and that's why you should probably lift your sights a little higher in your expectations. You really should assume that you are probably going to get a better lens, eventually. Within that line of thinking, already having a good UV or polarizer should be a consideration. If you spend less than $70 for a polarizer-filter (CP), then you have probably goofed up your autofocus to some degree when using it.

Best way to check is to shoot the length of a yard stick, meter stick or tape measure.
Place your focal target (something 3-D, not flat) along it at some point just past the Minimum Focus Distance (M.F.D.) of your lens. {if your M.F.D. is longer than 3-feet ... just move the yard stick with your focal target, so that you can see the graduations in front and after the focal target}
Take an image (preferably on a tripod) w/o the filter
Without changing the settings or distance, add the filter, refocus and reshoot


At this point, you should be able to see the difference in image. Heck, shoot it a couple times (w & w/o filter), to repeat results and confirm. It should really open your eyes as to the image quality and impact your UV or CP filter is having on your photography.

[Rooz]

interesting case, i cant speak for the effect on the sony AF system which according to your example is put out by the additional glass. from my experiecne i've never had a problem with either AF or IQ from using B+W UV filters which are fitted to all my lens'.

[DonSchap]

'Rooz' - You just might want to make a slight mention that B+W CP-filters (not Linear) are about the MOST expensive available to the young photographers (even some older ones). A quick scan (http://www.bhphotovideo.com/bnh/controller/home?O=search&A=search&Q=&ci=4038&sb=ps&sq=desc&sortDrop=Relevance&ac=&bsi=&bhs=t&ci=4038&shs=77mm+polarizer&at=Brand_B%2BW&basicSubmit=Submit+Query) of prices and sizes is easily done at B&H ... and if this is the case, you can easily add another $100-$300 to your lens purchase. Again, depending on the optical quality of your lens ... you need to balance that on your "glass appreciation budget." ;)

Also, once you close down your aperture to f/4 or more ... who cares? It becomes a moot point.

[TheObiJuan]

I've noticed that the Tiffen UV filter that came on my most recent lens caused it to jump focus back and forth.
I removed it and replaced it with a B&W and have no issues.

[DonSchap]

You know ... since this is a bit of aperture issue ... I'm going to keep the UV-filter on the lens ... until I am indoors ... and then shed its skin with the lens cap removal. The lens cap can keep protecting the filter, in my pocket, while I get true focus through the aperture range.

[dr4gon]

I've noticed that the Tiffen UV filter that came on my most recent lens caused it to jump focus back and forth.
I removed it and replaced it with a B&W and have no issues.

Might be a Tiffen issue? No problems with a Hoya Pro-1D CPL and UV here.

[DonSchap]

and that was at f/2.5?

[Rooz]

'Rooz' - You just might want to make a slight mention that B+W CP-filters (not Linear) are about the MOST expensive available to the young photographers (even some older ones). A quick scan (http://www.bhphotovideo.com/bnh/controller/home?O=search&A=search&Q=&ci=4038&sb=ps&sq=desc&sortDrop=Relevance&ac=&bsi=&bhs=t&ci=4038&shs=77mm+polarizer&at=Brand_B%2BW&basicSubmit=Submit+Query) of prices and sizes is easily done at B&H ... and if this is the case, you can easily add another $100-$300 to your lens purchase. Again, depending on the optical quality of your lens ... you need to balance that on your "glass appreciation budget." ;)

Also, once you close down your aperture to f/4 or more ... who cares? It becomes a moot point.

yes they are expensive. you get what you pay for.

[DonSchap]

yes they are expensive. you get what you pay for.

Yes ... and if I had a Carl Zeiss lens for every time I have heard that clever response ... I would be selling them. :p

[dr4gon]

The CZ filters are supposed to match CZ lenses pretty well with the t* coatings, but I think it's quite gimmicky lol

[Rooz]

Yes ... and if I had a Carl Zeiss lens for every time I have heard that clever response ... I would be selling them. :p

it is true though Don. there are very few genuine bargains out there.:)

[seanhoxx]

The naked or not debate continues! I think maybe a filter is a tool for a time and a place? I bought into and so far follow the 'protection' thought line. I do agree if you are going to cover use quality I use Hoya smc and am happy so far, I do have a couple of Tiffens. I would think that with a CPL that quality would be much more important then filter quality? At this weeks ball games I am going to use the Tamron 70-200 unfiltered and see how that looks, and if it has any effect on some of my 'lack of focus' issues LOL

[TenD]

Yup, if you are going to use a filter, use a good one, you want it to work(transmit light)don't you? Tiffen has a reputation for making some of the worst filters out there, basically utter junk, poor in contrast, and terrible in flare. If you think you need a filter buy a good one, you've just spent a large amount of money on that lens for good optics, and now you're going to put a coke bottle bottom in front of it? Funny. Great optics deserve to keep their greatness, and putting a $30 window pane in front of them is not doing the lens' optics any justice.

The idea of the filter for protection was invented by the photo shops as a quick POS(point of sale)item with a high profit margin. While you are still in your sticker shock haze at what you just paid for that lens, a salesperson says "you'll need a filter to protect that new lens investment, won't you?" Yes they can help protect your lens(from dog nose prints, finger prints, salt spray, blowing dust/sand/ect.), but from a drop they offer little or no protection. They are excellent at doing what they were designed to do: filtering light, provided a decent MRC filter is selected.

The front element is far far stronger than any filter is, the filter will break at the slightest impact, while a front element can take quite a whack, and with a hood on, a front element would be pretty hard to smack. I personally have seen front elements with huge hacks in them and the lens still performing very very well. I've owned one, an 80-200 f/2.8L with a half inch by 1/16" wide and deep scar in it. The photos from it were awesome, I couldn't even tell there was anything at all wrong with the front element from the output.

Here's an example (http://www.lensrentals.com/news/2008.10.30/front-element-scratches) of how much damage a front element can take and still take OK photos. Sure the photos are about the grade of a cheap disposable camera, but look at the damage to that front element! You wouldn't expect to be able to get any kind of photo out of that lens, yet the photos are passible, the text is readable, and as stated in the article most of the IQ loss is probably due to a shifted element from the impact. No filter would have helped one iota in that damage, except by adding another layer of broken glass to grind into the front element potentially adding more scratches to the already seriously damaged element.

This argument will go on forever, I have NEVER seen any evidence anywhere that a filter has saved a lens from damage. All I ever see is anecdotal evidence in threads that are always started by folks justifying their filter for protection stance. The so called evidence is always "my filter is smashed and my lens survived therefore my filter saved my lens". There is never any shred of proof that if the filter wasn't there the lens would have been ruined. I've never have seen a thread started by a naked guy talking about how his hood saved his lens, those posts are always in response to filter for protection threads. The hood just works, even for a flying object to get in there, it has to be aimed pretty well. In a fall the hood takes the impact and spreads it back to the lens body. The front element isn't even involved, with a filter, the front element will very likely be involved, whether by collateral damage, or direct impact after it breaks with very little force.

Yet in the opposite vein, I have seen countless thread in which someone is complaining how their expensive XX-XX f/2.8 lens is performing poorly, flaring, back-focusing, front focusing, hazy, ghosting, etc. The question is then asked, "do you have a filter on it?", the answer is almost always "yes". Then the poster is asked to try it with their filter off, and almost always the trouble goes away.

If you feel you need a filter for whatever the reason you think you need it for, get a good multi-coated one. Hoya Pro-1 MRC, B+W MRC, ect. A cheap filter will never do that expensive lens justice, and in many cases will seriously degrade the wonderful optics the lens already possesses. Every filter changes the optics of your lens, however small, it still changes the light transmission of the lens it is placed on. In most cases if a good filter is used, that change is not at all noticeable, but it is measurable, and that's enough for me.