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09-13-2010, 12:50 PM   #1
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Pentax 50-135mm f/2.8 AF Slow

My two favorite lens to use on my K20D are the Pentax 50mm f1.4 and 18-250mm. I wanted to add another lens to my collection for wedding and portrait photography. I like the zoom of the 18-250mm and DOF of the 50mm. So I purchased the Pentax 50-135mm f/2.8 and have used it on a few occasions now. The AF is painfully slow compared to the 18-250mm. Way to slow for the moving people photography.

If this normal for the lens? Anything I can do to make it any better, besides MF all the time. Maybe it is the wrong lens for my needs. Any other lens suggestions?

09-13-2010, 12:58 PM   #2
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If you think it the wrong lens for your needs, then return it. No point in having an expensive lens as a camera bag decoration. Yes, SDM is slow compared to the AF screw drive. Or so it may seem. In MY observations, it may have more to do with the noise (of the focusing) than anything else. That is, with the other lenses you can hear the wrrrr zip pop and lock of the mechanism working. With the SDM lenses, you cannot. Focusing rules don't change with SDM. You still need contrast to focus for instance. The DA* does have the nice feature of quick shift in which you can help it get there and let the SDM take over at that point. I find it to be very fast when used in this way but I'm willing to work with it for the optical quality of that particular lens.

Now, if it's REALLY slow, that is, takes seconds to even Move, you may have a defective lens. It isn't as common on the 50-135 as with the (older) 16-50 lenses but it Does happen.

Oh, Welcome to the forums

09-13-2010, 12:59 PM   #3
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Sigma 100-300/4.
Maybe is too long for you but AF killed me! (and my left hand still hurts)
09-13-2010, 12:59 PM   #4
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Pentax's SDM is about 10% slower than their screwdrive system on comparable FLs, so I guess the slowness you're experiencing is just the way it is

09-13-2010, 01:12 PM   #5
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QuoteOriginally posted by stacylynn85 Quote
My two favorite lens to use on my K20D are the Pentax 50mm f1.4 and 18-250mm. I wanted to add another lens to my collection for wedding and portrait photography. I like the zoom of the 18-250mm and DOF of the 50mm. So I purchased the Pentax 50-135mm f/2.8 and have used it on a few occasions now. The AF is painfully slow compared to the 18-250mm. Way to slow for the moving people photography.

If this normal for the lens? Anything I can do to make it any better, besides MF all the time. Maybe it is the wrong lens for my needs. Any other lens suggestions?
SDM varies from lens to lens. I own DA* 55 f/1.4 and DA* 300 f/4. The motor is actually faster on DA* 300 f/4. It's also pretty fast on DA 17-70 (around as fast as screw drive on DA 16-45, on k20d). I never owned DA* 50-135, but from what I've seen, it's around as slow as DA* 55.
09-13-2010, 01:59 PM   #6
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If I return this lens, does anyone else have an suggestions on another lens I should get, in a similar price range?

Currently Have:
DA (star) 50-135mm f/2.8 - too slow AF, not wide enough
FA 50 f/1.4 - slow but as bad as ^, would like more range
DA 18-250mm

Looking at:
DA (star) 16-50mm (slow AF too because it is a (star)?)
DA 35mm f/2.8
Sigma 17-50mm f2.8
Sigma 24-70 f2.8
Sigma 18-50mm f2.8

Anyone use any of these?
09-13-2010, 02:11 PM   #7
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QuoteOriginally posted by stacylynn85 Quote
If I return this lens, does anyone else have an suggestions on another lens I should get, in a similar price range?

Currently Have:
DA (star) 50-135mm f/2.8 - too slow AF, not wide enough
FA 50 f/1.4 - slow but as bad as ^, would like more range
DA 18-250mm

Looking at:
DA (star) 16-50mm (slow AF too because it is a (star)?)
DA 35mm f/2.8
Sigma 17-50mm f2.8
Sigma 24-70 f2.8
Sigma 18-50mm f2.8

Anyone use any of these?
FA 50 f/1.4 has fast AF and is a very good lens. DA* 55 f/1.4 has slower AF...

DA* 16-50 f/2.8 has pretty fast auto-focus...but *seems* to break most often.

People like the Tamron 17-50 f/2.8 here and defend it, while I bash it for the *VERY UGLY* onion ring bokeh.
09-13-2010, 02:24 PM   #8
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QuoteOriginally posted by stacylynn85 Quote
If I return this lens, does anyone else have an suggestions on another lens I should get, in a similar price range?

Currently Have:
DA (star) 50-135mm f/2.8 - too slow AF, not wide enough
FA 50 f/1.4 - slow but as bad as ^, would like more range
DA 18-250mm

Looking at:
DA (star) 16-50mm (slow AF too because it is a (star)?)
DA 35mm f/2.8
Sigma 17-50mm f2.8
Sigma 24-70 f2.8
Sigma 18-50mm f2.8

Anyone use any of these?
Actually the FA50 f/1.4 I had focused pretty fast, but on to your question.

The DA*16-50 actually focuses fast when the focus works (with a good copy of the lens). I've shot sports with it with pretty good success. It's been my reliable workhouse lens for the past year for weddings and photojournalism.

The DA*200 is in the same price range as the DA*50-135 f/2.8 and has faster autofocus.

I haven't ever owned the Sigma 70-200 f/2.8 II (with HSM silent motor) but I hear that this a much faster focusing lens than the 50-135 f/2.8 and costs about the same.

The DA35 f/2.8 focuses fine. It has big focus range because it's a macro, though.

I haven't owned or used any of the other Sigmas you mentioned.

To replace the Pentax 50-135 I'd suggest choosing among four lenses, the Pentax DA*200 (best combo of size + image quality + silent autofocus), Sigma 70-200 f/2.8 II HSM (most versatile), Sigma 50-150 f/2.8 HSM (a bit smaller than the Sigma 70-200). Tamron also makes an excellent 70-200 f/2.8 that you can try.

09-13-2010, 02:33 PM   #9
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Perhaps you are not to late to make the switch if AF performance is the priority. Make no mistake, I use Pentax when AF performance is not the priority, but you can do much better with other zooms like Canon EF-S17-55/2.8 + EF70-200/4L IS. You will never get the same kind of AF performance from Pentax system, no matter how much you spent. Horses for courses, just the way it is.
09-14-2010, 01:04 AM   #10
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QuoteOriginally posted by stacylynn85 Quote
If I return this lens, does anyone else have an suggestions on another lens I should get, in a similar price range?
If you want to replace your 50-135 then in my opinion the obvious choice is Sigma 50-150 HSM.
09-14-2010, 07:08 AM   #11
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I tried a 50-135 a few days ago. Man, was it slow... Slower than I remember. I could focus faster manually.
It was in not so good light, but the subject had plenty of contrast. Maybe that's to blame, or my K10?
09-14-2010, 07:19 AM   #12
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Sigma 50-150 mm F2.8!

Last edited by JoepLX3; 09-14-2010 at 07:19 AM. Reason: Replaced "?" by "!"
09-14-2010, 10:29 AM   #13
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QuoteOriginally posted by wlachan Quote
Perhaps you are not to late to make the switch if AF performance is the priority. Make no mistake, I use Pentax when AF performance is not the priority, but you can do much better with other zooms like Canon EF-S17-55/2.8 + EF70-200/4L IS. You will never get the same kind of AF performance from Pentax system, no matter how much you spent. Horses for courses, just the way it is.
I agree with this advice. Fast AF, especially in lower light, is just not a Pentax strength. If that is your thing, you need to consider other brands. The 50-135 in particular is glacial.

I have posted this test that someone did in EV5 light (Pentax SAFOX really slows down below EV6) before:

[YT]http://www.youtube.com/watch?v=ngUcQUchHEU[/YT]

Last edited by PentaxPoke; 09-14-2010 at 10:34 AM.
09-14-2010, 11:54 AM   #14
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QuoteOriginally posted by stacylynn85 Quote
My two favorite lens to use on my K20D are the Pentax 50mm f1.4 and 18-250mm. I wanted to add another lens to my collection for wedding and portrait photography. I like the zoom of the 18-250mm and DOF of the 50mm. So I purchased the Pentax 50-135mm f/2.8 and have used it on a few occasions now. The AF is painfully slow compared to the 18-250mm. Way to slow for the moving people photography.

If this normal for the lens? Anything I can do to make it any better, besides MF all the time. Maybe it is the wrong lens for my needs. Any other lens suggestions?
I have DA*50-135 and as much as I like this lens, it is admittedly slow. I once was shooting at the wedding and I missed the shots when people were walking down the aisle. Luckily, I was a guest, not a hired gun. This lens is indeed slow indoors at the less than perfect light, but it is quite fine outdoors. I was shooting a parade recently with it and didn't miss any shots of moving people. I also have DA*16-50 for two years and it's my favorite lens. AF is fast, IQ is amazing and it never let me down. I have DA*200 and it's perfect too but I never used it to shoot a moving targets.
Hope this helps,
Efraim
09-14-2010, 01:54 PM   #15
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I sold my 50-135mm because it was so slow focusing, brilliant IQ but not much good if it can't hit the target. Saying that it is a positive speed demon when compared to the 55mm f1.4.

I use my MKI Sigma 70-200mm f2.8 instead.
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