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12-28-2009, 10:16 AM   #1
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How accurate is K20 autofocus with FA31mm Limited?

I'm thinking about buying an FA31mm limited. I was wondering, though, how accurate is auto focus when used with this lens wide open? I have an M 50mm 1.7 which I often use fully open and I find that the focus confirmation is often not accurate enough. Actually, I find it quite hard to get the focus right with this lens wide open... I often go by trial and error... but when I do hit the focus right the results are often amazing. So how does the 31mm ltd fare? The body I use is a K20.

12-28-2009, 11:34 AM   #2
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The 31 is fantastic wide open... this is one of the reasons why this is such a great lens and I have not had any trouble when using auto focus.


cheers

Neil
12-28-2009, 12:19 PM   #3
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Well on my K10D I had severe problems focusing the FA31. Felt like the lens did not give enough contrast to focus properly. I had the same problem on 2 copies of the FA31. You, on the other hand, have the K20D and I have heard that AF is better on the K20D even if the tech sheet says it's the same AF system.

I might have had a case of real bad luck though..
12-28-2009, 12:26 PM   #4
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Never used the 31ltd on my K20... but I did get to use the 77ltd wide open and I was stunned how well it AF'd on the K20. I would imagine the 31 wide open should be at least as good.

12-28-2009, 12:55 PM   #5
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QuoteOriginally posted by Scrib Quote
I'm thinking about buying an FA31mm limited. I was wondering, though, how accurate is auto focus when used with this lens wide open? I have an M 50mm 1.7 which I often use fully open and I find that the focus confirmation is often not accurate enough. Actually, I find it quite hard to get the focus right with this lens wide open... I often go by trial and error... but when I do hit the focus right the results are often amazing. So how does the 31mm ltd fare? The body I use is a K20.
Just a fast suggestion, hope it's not too trivial. But, is your K20D updated to the latest firmware? I seem to recall the last firmware update did not indicate any changes to the AF, still many people seemed to feel it improved the speed and accuracy. But, that could be simply wishful thinking/placebo effect yet updating won't be a bad thing.
12-28-2009, 01:18 PM   #6
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I have a K20, with the latest firmware update, and a recently acquired FA31. It auto focuses instantaneously and has never hunted - not even once. All my other lenses hunt to varying degrees.

Now after saying that, I have been doing some stitched panos, so I have been using manual focusing at the hyperfocal distance usually using f5.6 - seems the be the best and the lens test sites confirm it. I got excited about f1.8 the focus is extremely good, but for the landscapes, in low light, with some foreground items, I have been going after, stopping down works a bit better.
12-28-2009, 01:37 PM   #7
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QuoteOriginally posted by brecklundin Quote
Just a fast suggestion, hope it's not too trivial. But, is your K20D updated to the latest firmware? I seem to recall the last firmware update did not indicate any changes to the AF, still many people seemed to feel it improved the speed and accuracy. But, that could be simply wishful thinking/placebo effect yet updating won't be a bad thing.
That's a good suggestion, though. Thanks.

Now I have to figure out whether I can actually afford this glass :P
12-28-2009, 01:38 PM   #8
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Same - K20D + 31ltd = bliss.
Even in low-light, the AF worked reasonably well, and accurately in wide open shots.

12-29-2009, 12:09 PM   #9
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Went to a shop today in Amsterdam and they were able to sell me a 31mm ltd in silver for 900 euros and one in black for 1000 euros... is this difference in price common? I'd prefer black (a little bit more inconspicuous) but I'm not sure it's worth 100 euros to me.

Anyway, gonna hunt a bit further for a better deal methinks.
12-29-2009, 02:56 PM   #10
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in the US the silver is almost always the more expensive version. Either price is a fair bit of money but what the heck...word of warning about the sliver versions of the FA ltd's...once you have one in silver you will NEED the other two in silver as well...I think it is a "secret chemical" in the metal that gets you addicted to the color!!
12-29-2009, 05:07 PM   #11
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The FA 31 AFs quite well wide open on my K7. I have had several rejects using AF @ 1.8 when shooting small objects at a relatively close distance. I definitely can't MF any better in those situations than the camera.
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