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08-27-2011, 11:02 PM   #1
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50-135mm on K-5

I am thinking of buying a 50-135mm*, but the complains that the AF is slow really make me reluctant. I want to catch my kid's face. She moves all the time as other little ones..
Well, I do remember somebody in this forum said that the 50-135 is a lot faster on his K-5. Has anybody here ever done such a comparison? Such as the focusing speed between a K-5 and a K-7/K20/k10 body?

Regards,
Feishui

08-27-2011, 11:40 PM   #2
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Size was an issue for me. Focus was better compared to the K200D. I'm finding I take a lot more photos of my kid already with it's replacement, the FA77. Both are amazing lenses.
08-27-2011, 11:50 PM   #3
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The 50-135 has the rep of a slow focusing lens. I personally love it, and the focus is fast enough for me. But for fast moving kids... dunno.
Issue here is how much the lens has to move to achieve focus, not the actual focus confirmation.

The lens is the limiting factor, not the camera. K-5 AF is actually fantastic compared to K20D. I am using AF-C, and the results are very satisfying.
The only improvement I'd like to see is a kind of AF tracking, where the camera is keeping a target in focus while it is moving across the frame, similar to LV.
That would be of real help with the kids.

Octav
08-28-2011, 01:00 AM   #4
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I just have to say that I think that this claim about a slow AF is ridiculous. I'm backing up this bold statement with experience in the 50-135 with the K100D, K10D, K-7 and most recently K-5. I've used it alot when shooting football and I've never had any issues. When the lens has to focus from near to infinity or vice versa it'll take like a second because of the focus throw but nobody can move that fast anyway.

08-28-2011, 01:46 AM   #5
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My 50-135 focus's faster on my K10D than on a friends K5. I havnt had any problems at all with focus. Low light or moving objects.
08-28-2011, 09:45 AM   #6
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I say focus is alright, it is not too slow nor is it blazing. I think kis shots are doable
08-28-2011, 09:48 AM   #7
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If you want a faster lens, look into the Sigma 70-200mm. Rear-mounted SDM AF by Sigma is much more effective.

AF on the K-5 is more accurate, but it won't be noticeably faster than that on other bodies as the lens motor is to blame. Overall, Pentax's SDM is about 10% slower than standard screwdrive (except on the DA* 55, which is worse).
08-28-2011, 09:52 AM   #8
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QuoteOriginally posted by x-country Quote
I just have to say that I think that this claim about a slow AF is ridiculous.
I'm not sure why you would make that statement. The AF of the 50-135 is slow relative to other similar AF lenses (70-200, 80-200, etc). About the only Pentax lens I can think of with slower AF is the DA*55.

That said, is the AF fast enough in most situations? Yes.
Is it ideal for fast moving kid shots? No, not ideal, but it's certainly not useless either.

08-28-2011, 11:44 AM   #9
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Thank you all for the nice input
QuoteOriginally posted by Adam Quote
Pentax's
QuoteOriginally posted by dgaies Quote
About the only Pentax lens I can think of with slower AF is the DA*55
SDM is about 10% slower than standard screwdrive (except on the DA* 55, which is worse).
I don't have a DA*55, but If it is slower than my 50F1.4, then I would be very worried it is too slow for kids' shooting.
I thought about Sigma, as they are in a similar price/FL range, but to carry a 3pound lens around? It might be a little bit too much for me...
08-28-2011, 11:47 AM   #10
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QuoteOriginally posted by feishui Quote
Thank you all for the nice input


I don't have a DA*55, but If it is slower than my 50F1.4, then I would be very worried it is too slow for kids' shooting.
I thought about Sigma, as they are in a similar price/FL range, but to carry a 3pound lens around? It might be a little bit too much for me...
The DA*55 isn't a great (fast moving) kid shooter. Again, it's not like you can't get great shots with it, it's just no the ideal tool due to the relatively slow AF.

And from what I recall, the AF of the DA*55 is slower than the FA50/1.4 (I no longer have the FA50/1.4).
08-28-2011, 11:58 AM   #11
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You could rent the 50-135 lens here and judge for yourself:

CameraLensRentals.com - Pentax Telephoto Lens Rentals

Ultimately, for things like AF speed to take pics of your kids, you are the only one who can judge adequacy. The lighting condition and the distance to subject that you usually shoot from are also going to matter.

I have the 50-135 and K5, I use it to take shots of my kids in sport and dance and often use Hi speed shooting mode. Serves my needs really well.
08-28-2011, 03:55 PM   #12
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The AF of the 50-135 is definitely fast enough for taking photos of moving kids in my experience. The biggest problem I have with kid shooting is them moving between focus lock and the shutter going off (caused by focus recompose or waiting for SR), and the large size of the AF points which is a problem sometimes with very wide apertures. Neither of these issuess relate to the lens but to the body. To minimise these issues I'm having a bit of success now with using AF-C and off centre AF points which in the K-5 are a lot easier to use than on the K-x.
08-29-2011, 12:44 AM   #13
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I've been using the 50-135 with a K10D, K-r and now a K-5 for shooting moving targets (concerts and my toddler daughter). The speed isn't super fast but but I'd never get rid of this lens, what I usually do is a test shot to get the focal length in focus and then shoot from there and it's pretty quick. With this photo, she was spinning around.
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08-29-2011, 12:56 AM   #14
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The DA*55 is definitly more than fast enough for kids at play.

Had no problems locking on at f/2 on this shot-
08-29-2011, 07:17 AM   #15
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QuoteOriginally posted by TOUGEFC Quote
The DA*55 is definitly more than fast enough for kids at play.

Had no problems locking on at f/2 on this shot-
Great shot

However, if you were to try the same shot 90 degree from where you took it, my question is how well would the lens focus with your son moving towards you as you tried to take the shot. I realize, as twitch said a few posts back, that a large part of that issue is the speed of the AF within the body, and not just the lens itself. That said, using AF-C with a lens like the DA40 or FA*85 (both of which are very fast focusing lens) should give you an advantage over using either the DA*55 or DA*50-135 in a situation as I decribed. At least that has been my experience.
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