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05-30-2007, 03:21 PM   #1
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Slow focusing w/50mm f1.4?

I recently purchased the FA 50mm f1.4 lens, mostly to try out a prime lens, but also because I wanted to be able to take indoor shots (with decent lighting) without using a flash.

I've noticed that this lens seems somewhat slow to focus given the low aperture it's capable of. The slow focusing is especially aparent if the subject is moving (although rather slowly).

My body is the DL (for now, hopefully will upgrade soon), so I know this isn't helping either. The problem is that the 50mm appears slower to focus than the kit lens (18-55mm), has anyone else experienced this, or could they perhaps offer some pointers?

05-30-2007, 03:52 PM   #2
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My 50 doesn't focus slow in respective to the other pentax lenses I have. It is slower than USM of course, but that's a given. I think if you get a better body like the K10D you may see a difference. It is an older lens going back to the film era, so the focus may not be as fast. On digital, this lens performs exceptionally well IMO.
05-30-2007, 04:35 PM   #3
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I've used this lens at sporting events and have had no problems with AF tracking my subjects. I shoot with a K10 though.
05-31-2007, 06:40 AM   #4
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the 3 point af system of the dl can't focus the wide aperture of the fa50 fast. i shot with a dl for a little over a year with that lens, and it's possible to get good shots but it takes a lot of hunting or manual focus.

on the k10d, it's unbelievably faster.

05-31-2007, 09:47 AM   #5
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QuoteOriginally posted by attack11 Quote
the 3 point af system of the dl can't focus the wide aperture of the fa50 fast. i shot with a dl for a little over a year with that lens, and it's possible to get good shots but it takes a lot of hunting or manual focus.

on the k10d, it's unbelievably faster.
I'm using centre-point AF, wouldn't this help make it faster (since it's always focusing on the same point)?

In any case, it looks like I have an excuse to get a K10D in the future
05-31-2007, 10:15 AM   #6
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i shot exclusively with the center point, and it helps just a little. unfortunately, the dof is so shallow you know how it likes to hunt

it needs a cross point af to really shine.
08-22-2007, 06:29 PM   #7
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Myself, I received today a FA 50 1.4 and the first thing I noticed is that the 50 1.4 is focusing slower than the 18-55 Kit lens on the K100D. Not all the time, but it hunts more sometimes.

But it was almost evening outside when I tested it so maybe is just my imagination, I will try to make more tests in different conditions.
08-22-2007, 10:18 PM   #8
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the DOF is very thin at f1.4 so unless you are on a tripod/shootin straight on, any subtle movement is enough to change the focus on center and require a focus adjustment.

08-23-2007, 03:10 AM   #9
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I have the same problem and I have the Pentax DS. Is there any techniques to improve autofocusing speed?

I've read you can use the built-in flash to help with the autofocus - but I dont want the flash to be used when the photograph is actually taken. Is there a way to do this?
08-23-2007, 04:22 AM   #10
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switch the dial to "MF", roll the focus ring until the desired person or subject in the viewfinder turns crispy, take a deep breath and shoot away. :P
08-23-2007, 05:00 AM   #11
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QuoteOriginally posted by FotoPete Quote
switch the dial to "MF", roll the focus ring until the desired person or subject in the viewfinder turns crispy, take a deep breath and shoot away. :P

I'd like you to try that with a hyperactive 3 year old
08-23-2007, 07:25 AM   #12
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QuoteOriginally posted by ngkmh Quote
I have the same problem and I have the Pentax DS. Is there any techniques to improve autofocusing speed?

I've read you can use the built-in flash to help with the autofocus - but I dont want the flash to be used when the photograph is actually taken. Is there a way to do this?
Try bumping up the ISO manually. The AUTO mode will insist on staying on low ISO as much as possible.

Last edited by song_hm; 08-23-2007 at 07:26 AM. Reason: addendum
08-23-2007, 08:59 AM   #13
raz
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After testing it more in good light outside I can say , that yes, it's slower than the kit lens at autofocus. Sometimes it seeks for a long time when you are on center focusing and is not acquiring focus at all (fortunately it doesn't happen to often), but this almost never happens with the 18-55.

And to my knowledge, it doesn't matter what aperture are you at, and what ISO or any other setting, the autofocus should be independent of that and only be influenced by the light outside and the contrast of the subject.

But besides that, I'm extremely happy of the image quality, color contrast and bokeh are beautiful, and also the focus is spot on, I was affraid I will have front/back focus issues, but is not the case. Even at 1.4 I have some pictures that are sharp (to my surprise ) You can see the image bellow (taken in jpg, cropped, resized 50%).

Click after the image is open to expand on the screen otherwise it's resized by imageshack I guess.

Last edited by raz; 08-23-2007 at 09:04 AM.
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