"L" stands for lemon

First off, thanks to everyone for commenting and providing suggestions. One of the suggestions made me think of a Sherlock Holmes quote that went something like "if you eliminate the logical possibilities, then whatever is left, regardless of how illogical, must be the reason."

To make a long story short, I discovered that the source of my focusing problems is.........
a bad UV filter! I discovered this pretty much by accident this weekend. I was at the beach and replaced the filter normally on the lens with a polarizer, and noticed that the shots looked even more blurry than usual. So, I removed the filter altogether and (drum roll) - no more blurry photos. I always removed the filter when I sent the camera to Canon for the repairs, so they never identified it as a problem. I've checked it numerous times now and the result is the same - tack sharp without the filter, blurry with it. I tried with a different 67mm filter, and again, no problem focusing.

So, all my frustrations, crappy photos, etc., due to a cheap-ass UV filter made by "Digital Concepts" (made in China).

Thanks again!

leo_jb wrote in post #10317675
First off, thanks to everyone for commenting and providing suggestions. One of the suggestions made me think of a Sherlock Holmes quote that went something like "if you eliminate the logical possibilities, then whatever is left, regardless of how illogical, must be the reason."

To make a long story short, I discovered that the source of my focusing problems is.........
a bad UV filter! I discovered this pretty much by accident this weekend. I was at the beach and replaced the filter normally on the lens with a polarizer, and noticed that the shots looked even more blurry than usual. So, I removed the filter altogether and (drum roll) - no more blurry photos. I always removed the filter when I sent the camera to Canon for the repairs, so they never identified it as a problem. I've checked it numerous times now and the result is the same - tack sharp without the filter, blurry with it. I tried with a different 67mm filter, and again, no problem focusing.

So, all my frustrations, crappy photos, etc., due to a cheap-ass UV filter made by "Digital Concepts" (made in China).

Thanks again!

All I can say to that is... wow

leo_jb wrote in post #10317675
First off, thanks to everyone for commenting and providing suggestions. One of the suggestions made me think of a Sherlock Holmes quote that went something like "if you eliminate the logical possibilities, then whatever is left, regardless of how illogical, must be the reason."

To make a long story short, I discovered that the source of my focusing problems is.........
a bad UV filter! I discovered this pretty much by accident this weekend. I was at the beach and replaced the filter normally on the lens with a polarizer, and noticed that the shots looked even more blurry than usual. So, I removed the filter altogether and (drum roll) - no more blurry photos. I always removed the filter when I sent the camera to Canon for the repairs, so they never identified it as a problem. I've checked it numerous times now and the result is the same - tack sharp without the filter, blurry with it. I tried with a different 67mm filter, and again, no problem focusing.

So, all my frustrations, crappy photos, etc., due to a cheap-ass UV filter made by "Digital Concepts" (made in China).

Thanks again!

Welcome back Leo..

Sub quality filters can be a real problem.. My suggestion is to throw those filters in the rubbish bin.. If you want to look at filters try the top grade ones from Hoya or B-W..

Welcome back Leo - I'm glad that 5 pages of replies and chatter didn't scare you off and I'm glad that you were able to find the factor that was causing your problems!
I also agree with yogestee - if you want ot keep using filters (and some like circular polarizers are needed for certain effects that cannot be reproduced in editing) then look to the pro brands. Expensive good quality filters are worth their cost, just as your lens is worh its high cost.

I used a good filter on my 70-200 4.0 L. That was the last time I used a filter. Glad you solved your problem.

This thread should be a sticky. Glad you found your issue.

great follow-up Leo, and your learning experience was a great contribution. I'm still laughing at all the other assumptions and conjecture that were quite entertaining as well!

On a personal note, I decided not to hang a UV filter on my 70-200, mostly because the lens hood is so substantial I did not feel the need to protect the front lens element with another layer glass. I have, however, put the B+W 77mm MC UvA #010 ($92) on my 17-55 f/2.8 IS. My only regret here is that when I'm in situations where the polarizer goes on, its kind of a bother having to remove the UV first...

For the circular polarizer I also turned to B+W; my 77mm Kaeseman Slim is wonderful, but also $175. I suspect it might end up on my 70-200 on occasion. CPLs work as a ND filter even when there is no polarized light to filter anyway, if you choose to purchase a CPL, the 67mm variety will be less expensive!

All the best with your 70-200!

dlleno wrote in post #10318003
great follow-up Leo, and your learning experience was a great contribution. I'm still laughing at all the other assumptions and conjecture that were quite entertaining as well!

On a personal note, I decided not to hang a UV filter on my 70-200, mostly because the lens hood is so substantial I did not feel the need to protect the front lens element with another layer glass. I have, however, put the B+W 77mm MC UvA #010 ($92) on my 17-55 f/2.8 IS. My only regret here is that when I'm in situations where the polarizer goes on, its kind of a bother having to remove the UV first...

For the circular polarizer I also turned to B+W; my 77mm Kaeseman Slim is wonderful, but also $175. I suspect it might end up on my 70-200 on occasion. CPLs work as a ND filter even when there is no polarized light to filter anyway, if you choose to purchase a CPL, the 67mm variety will be less expensive!

All the best with your 70-200!

Im glad you laughds at all the other "conjectures" because in the end IT WAS user error...a crappy filter that should have been thought off a long time ago qualifies as a user error in my book.

Im glad it was all sorted out, my advice forget about ANY UV filter....naked is better:p

Brain Mechanic wrote in post #10318188
Im glad you laughds at all the other "conjectures" because in the end IT WAS user error...a crappy filter that should have been thought off a long time ago qualifies as a user error in my book.

Im glad it was all sorted out, my advice forget about ANY UV filter....naked is better:p

dude. I'm laughing at the stuff about a possible troll, hijacking the thread, and other entertainment that generated more heat than light! not the constructive user error comments which turned out to be true.

Interesting that some people equate using a filter to "user error." I never suspected the filter could affect focusing. Which brings me to a question. I've always used a filter for fear of scratching the lens, but maybe this fear is misplaced. How many of you shoot without a filter?

leo_jb wrote in post #10318500
Interesting that some people equate using a filter to "user error." I never suspected the filter could affect focusing. Which brings me to a question. I've always used a filter for fear of scratching the lens, but maybe this fear is misplaced. How many of you shoot without a filter?

If you use a high quality filter then you should be good.

I took some shots of my daughter's soccer game with my 70-200 f4 non-IS and also noticed at further distances, 200mm wide open they were OOF. Shot handheld in AI Servo, center point focus, using * focusing. Probably 1/500 at least, will need to check. At close distances and shorter FL, it is very sharp.

I'm debating on whether to upgrade to MFA caapable camera or send it in. I seem to notice some issues (sometimes) with my 85 1.8 as well. I know someone with 7D I might be able to try it on.

Based on my experiences, that of another poster in this thread, and another thread from a few weeks ago, it seems like there could be issues with this highly-touted lens.

yea I think the "user error" was not about using a filter per se, it was about using a low quality one. that aside, the filter IS an after-market addition that is not part of picture when Canon tests and repairs their lenses. So in that sense you'd have to admit to some user error not to remove it as a test. Thing is, optical abberations confuse the AF system which (as you can imagine) was developed and tested without one, and degrade IQ. much like looking through a window. But Filters from the likes of B+W won't behave like that (unless they're dirty).

I'd say my filter philosophy is shifting a bit more to the naked side . Especially when you have longer lenses with substantial hoods (like the 70-200), and glass pushing the state of the art in sharpness I can honestly see the merit of naked. I admit, however, to starting out in your camp - the familiar "cheeper to replace a $100 filter than repair the lens" approach. Yet, even from the 1970s the only filter I've damaged is one that wasn't on a lens . and back then my lenses had no hoods!

I put a uv filter on my 17-55 because I had read about this lens' susceptability to dust and that the filter helps that situation. The hood for this lens is also rather wide, so the protection argument makes more sense, especially considering that my 17-55 goes to the beach with me. On the flip side, another layer of glass can introduce additional lens flare. For those familiar with lens phyiscs you know that every time light goes through a change in media (air to glass, glass to air) there is both transmitted and reflected light, depending on the angles involved; hence all the coatings and other efforts to minimize this.

So one has to strike the right balance between assessing the real and present risk of danger to the lens, versus the potential trade-off of IQ, given the lens you have, the available filters, your budget, and the enviroment in which you shoot. For me, an expensive UV filter on a 17-55 makes sense for where mine goes. But as I mentioned before I have no plans to hang an additional layer of glass onto one of the sharpest zooms known to man that has a generous protective hood anyway.

This has probably already been done, and may be difficult, but I'm feeling the urge to test the "with vs without" situation with my 70-200 f/2.8 IS II when it arrives this week.

Absolutely no disrespect to the OP, but it took returning the lens to Canon three times before you realized that the filter was the issue? Did it really not occur to you to remove the filter and test the lens out at anytime before, during or after all these trips to and from Canon? They must have thought you were having some kind of big joke

Anyway, glad it's working for you now

leo_jb wrote in post #10318500
Interesting that some people equate using a filter to "user error." I never suspected the filter could affect focusing. Which brings me to a question. I've always used a filter for fear of scratching the lens, but maybe this fear is misplaced. How many of you shoot without a filter?

Yours would be a Frisbee in my hands.

This subject has been beat to a pulp with pros and cons so many times with so many verbal murders committed over it, it's ridiculous. I say absolutely no "protective" filters. A scratch on your front element would have not affected your images at all, but look what your "protective" filter did for you.

My front element protection consists of normal care and awareness using my gear, lens hoods and caps, and I find I rarely need to clean the front element more than puffing it off with a bulb blower when I notice something on the lens, it never shows on images. My lenses have seen the world and are in great shape. If peeps don't trust themselves to look after their gear in simple ways, let 'em wear filters and risk their images.