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DPChallenge Forums >> Hardware and Software >> Circular Polarizer on 350D - Focusing Problems
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Showing posts 1 - 9 of 9, (reverse)
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 05/11/2005 06:50:40 PM · #1
I went and bought a Hoya circular polarizer - to replace the one I dropped in the harbor a few months back :( - for the kit lens and/or the G5. I got the non-coated cheap version - I'm going to wait till I get some new lenses to decide on the size for a better coated version.

When I tested it out yesterday and today, I found the lens/camera has trouble focusing about 20% of the time. It will hunt for a couple of seconds, then settle on being totally out of focus and the focus light blinks (or goes out - I foget which indicates no focus). Is this normal for a circular polarizer on a DSLR? Or is the filter defective? I used this same model filter on the G5 for about a year with no problems - well, except that time it slipped and fell in the harbor. But I can't blame that one on Hoya.

I did notice when I opened the filter that there was a smudge in the middle. I cleaned it with a lens pen - not thorough, but it seemed to get the smudge off. And I also noticed a lot of lines on the filter - maybe like hairline scratches? They only show up at certain angles under bright sunlight. I don't recall seeing these on previous C-PLs I've had, but....?

So, does this sound like a bad filter? That's my assumption, but wanted to see if anyone else has used a C-PL on a DSLR before, and particularly on the DRebel kit lens, and what their experience was - ammo for the return trip to the store.
 05/11/2005 06:54:30 PM · #2
You might have a linear polarizer instead of a Circular polarizer. With a CPL there is no reason for autofocussing to fail unless you are already in really low light...
 05/11/2005 07:52:11 PM · #3
Nope, got a circular - I know the issue of linear with DSLRs. And, I guess I forgot to mention, but it was a bright, sunny day. The first time I noticed I was focusing near the horizon, which was a little hazy, so I thought that might be the problem. But as I went on, things that should have been no problem - like a palm tree about 50 feet away against the blue sky - would have the problem.
 05/11/2005 07:59:31 PM · #4
I have 4 different CPL's and never had such an issue,maybe your lens sucks :-(
 05/11/2005 08:01:09 PM · #5
...which is why I'm asking if anyone's had this problem with the kit lens. :)

If this is common with this lens, I don't want to go back whining to the store and have to fight with them from a position of weakness.

Message edited by author 2005-05-11 20:02:23.
 05/11/2005 09:11:30 PM · #6
Originally posted by ScottK:
...which is why I'm asking if anyone's had this problem with the kit lens. :)

If this is common with this lens, I don't want to go back whining to the store and have to fight with them from a position of weakness.

I did have problem using 6 other focusing points{center worked ok) with the kit (crappy) lens when polarizer is attached.That was the last time I used that lens.

Message edited by author 2005-05-11 21:12:28.
 05/11/2005 09:44:50 PM · #7
Here's a theory--more like a guess.

Could it be related to the fact that when the lens is trying to focus, the polarizer is turning, thus changing the contrast and defeating the AF?

Like I said, a wild guess, but since I see you haven't received any solid info yet, I figured I toss a theory into the hat.

I don't recall having a problem, but I haven't used my kit lens since about 2-3 weeks after I got my camera in Oct.
 05/12/2005 01:08:01 PM · #8
Interesting idea Neal. That does seem like a possibility. I'll see if I can somehow test that. Though the problem is a little hit and miss. Thanks for suggesting it.

Kosta: I haven't even tried it with the outer focus points, so maybe they're even worse. I'll test that too. Since I'm still in the "honeymoon" phase, just upgrading from a P&S, I don't really view the kit lens as crappy (yet). Its mostly as good or better (except the zoom range) as what I've worked with for the last two+ years. But I definitely am on the hunt for better glass. Like I said (or tried to imply), I intended this mostly as a temporary for the kit lens, then move it back to the G5 when I get better. But while I didn't expect the greatest quality, I expected it to be functional.

Thanks for the replys guys.
 05/12/2005 01:20:02 PM · #9
BTW--Best inexpensive replacement for the kit lens is the Sigma 18-125 for $250. Gives you much more range, comes with a hood, not too large. It doesn't turn when you focus. It's noisier than the Canon USMs when focusing but not a major problem, and its very sharp with good colors.

Theres also a more expensive 18-200 now, which I haven't tried, but others on the site have.

If you don't need the wide end (but I think most people do) and you want a nice 2.8 fixed lens, look at the Tamron XR Di f2.8 28-70 (I think that was the range--there have been many posts raving about this).

As soon as I got my Sigma, I've never used the kit lens (well, I did hold it backwards in front of the 50 1.8 once as a macro lens). ;)
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