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05-12-2016, 01:53 PM   #1
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DA* 55mm vs DA* 50-135mm AF speed

I love my 50-135mm for its color and sharpness. I am looking at the 55mm and am blown away at the photos coming out of it. I want to know if the AF speed is comparable to the 50-135mm. Does anybody have experience with both? Which is better?

05-12-2016, 02:55 PM   #2
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I have both, so I could possibly make a quick and dirty video comparing the two later tonight. However, my 50-135mm has a new motor in it while the DA 55 doesn't and does make a faint but audible high pitch sound, so it's hard to tell if it focussed at the "normal" speed. I can't complain though as it seems to focus like it should all of the time.
What distance would you like me to test the focusing speed at? Portrait like distance, say within 5 meters?
05-12-2016, 03:32 PM   #3
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Honestly, I have had both of these and I thought the 55 was glacially slow. Absolutely fantastic image quality but af was painful, really.
That was 2 years ago on K5 body so maybe on newer body it might be quicker.
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05-12-2016, 04:29 PM   #4
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Awesome! A test would be great. I would be using this as a portrait lens so i think 5m would do the trick.

05-12-2016, 07:03 PM - 2 Likes   #5
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Alright, testing with only one body is rather difficult, but I still did a quick and dirty test that hopefully will help you assess the situation, at least a little bit.
Camera : Pentax K-5ii
Focus mode : single center point
Light level : fairly dim, all indoor lightings, settings for proper exposure were about iso 2000-3200, f/2.8 at 1/125th of a second
Target : the side of a grey shoe box with big letters, about 4 meters away

Approximate results:
Times are in seconds. So, in this case, 0,51 means 51/100th of a second. I think it makes sense, I just used my editor (Final Cut) timeline to approximate the time.




*It failed to acquire focus, I had to repress the shutter, then it acquired focus. I repeated several time and it was just a lone incident.

video :
I'm sorry for the video. I tried to do something quickly that would allow for an "easy" visual comparison, but I quickly realized it would take me a lot of time to make it right, so I ended up doing something that I find pointless, but some of you may benefit from it, so I post it anyway. However, I figure you could just ask me for the original videos and you could then sync them yourself and maybe time them on a more precise fashion.



Finally :
While I had the camera set up, I figured I would test some other lenses that might be of interest for portrait work, or for general AF speed concerns.
Therefore, I have similar videos for the following lenses, all taken minutes from each other in the same light condition, at the same approximate distance of 4m :
Pentax DA*55mm f1.4
Pentax DA* 50-135mm f2.8
Pentax DA* 60-250mm f4
Pentax DA ltd 70mm f2.4
Pentax F 50mm f1.7

If you would like access to any of the videos to make your own comparison, just pm me, I'll send you a link for download.

I have not calculated the time for the other lenses, but I plan to do it eventually. The F 50mm 1.7 seems quite fast.

Last edited by kp0c; 05-13-2016 at 04:04 AM.
05-13-2016, 06:27 AM   #6
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Very Helpful! It seems the "slow" focus everyone is talking about is actually almost the same as the 50-135mm. I am thinking it will be perfect for my use.

I would be interested in your other videos if you dont mind sending them to me.
05-13-2016, 05:48 PM   #7
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QuoteOriginally posted by Blacknight659 Quote
Very Helpful! It seems the "slow" focus everyone is talking about is actually almost the same as the 50-135mm. I am thinking it will be perfect for my use.

I would be interested in your other videos if you dont mind sending them to me.
Yeah! No problem. I might as well just share a web link so that anyone can download them and make their own assessment.
Link to download the files : https://mega.nz/#F!AcQB2Bza!BlIAGcju-bqSmq9401eUWg

---------- Post added 05-13-16 at 09:29 PM ----------

I have updated the test results :


The F 50mm 1.7 is imo very fast to acquire focus, so is the DA 70mm ltd. All the SDM zooms are slow, with the 60-250mm being the slowest.

I also wanted to share my experience using the 55mm 1.4. I bought it a few weeks ago for my wedding photography contracts* and I was still unsure just how much useful it was gonna be outside of the portrait session. I tried it around my kids in the past few days and I do find the focusing speed limiting. I'm not sure I will be confortable using it in the midst of the action during the ceremony (with people walking down the aisle for instance) and probably not during the dance and similar stuff as well. If I need a fast 50mm, the f 50mm 1.7 will have to do I think.
Since you said you were happy with the AF speed of your 50-135mm, I think it's safe to say that you should enjoy the 55mm 1.4 just fine! It's really a great lens to use as it delivers lovely images.


*I have been doing a couple of weddings in the past years to generate some income that I then use to upgrade my equipment - but I am definitely not a pro wedding photographer, nor do I ever want to be. I have 3 planned so far this year.

Last edited by kp0c; 05-13-2016 at 06:31 PM.
05-14-2016, 02:13 PM   #8
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I just did a shoot today and Boom... the SDM is failing. I am considering switching to Screw drive, but I also considered selling and buying a 70mm 2.4 (I regularly shoot from 60-90mm, 70 would probably do me just fine). Can you speak to the image differences on the 50-135mm @ 70mm vs the 70mm lens?

05-14-2016, 03:42 PM   #9
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I can't speak about the 70mm, but the 50-135 performs great with screw drive
05-15-2016, 04:11 AM   #10
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QuoteOriginally posted by Blacknight659 Quote
I just did a shoot today and Boom... the SDM is failing. I am considering switching to Screw drive, but I also considered selling and buying a 70mm 2.4 (I regularly shoot from 60-90mm, 70 would probably do me just fine). Can you speak to the image differences on the 50-135mm @ 70mm vs the 70mm lens?
The 50-135mm is a special lens. It is sharp enough at 2.8 and offers a sublime rendering. It also works very well with screwdrive focus, so I do encourage you to convert it. As for the comparison with the 70mm, I'm certainly not able to say with certitude that the ltd offers any image quality upgrade. From memory, the 70mm might be a little sharper at 2.8 than the DA*, but it doesn't offer much speed advantage with its 2.4 maximum aperture. Honestly, I've had the 70mm for a while now, well over a year, and I still haven't clicked with it. If I had to choose between the 70mm and the 50-135mm, I'd keep the zoom in a heartbeat.
I keep the 70mm for it's much quicker focus and because it is light and small. When I go out with my camera to relax and take pictures, I prefer to carry small lenses and since I usually carry my camera with me everywhere I go (during transit everyday of the week), I'll take the 70mm with me if I want a medium telephoto lens.
So, in your case, if you don't see a distinct advantage in having the 70mm focal length covered with a very small lens, I wouldn't buy it. I'd convert the 50-135mm and use it.
Now, if you were interested in the 77mm, I'd say it offers enough of a speed difference as well as some more artistic opportunities to go for it in addition of your zoom.
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