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02-15-2020, 04:02 PM   #1
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Pentax 24-70 f2.8 - slow AF?

I bought the lens used on Adorama but it was in E condition (or what ever is 2 levels below demo). I see 2 spots on the glass but neither have appeared in any image.

Compared to the Tamron 70-200mm f2.8 and Sigma 18-50mm f2.8, the Pentax is slow to focus. That's only an issue since I'm trying to shoot baseball and I'm not good enough to manual focus sports.

Just wondering if this is normal. Otherwise, the lens seems to be fine and it does take good photos.



02-15-2020, 04:12 PM   #2
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QuoteOriginally posted by jspi Quote
I bought the lens used on Adorama but it was in E condition (or what ever is 2 levels below demo). I see 2 spots on the glass but neither have appeared in any image.

Compared to the Tamron 70-200mm f2.8 and Sigma 18-50mm f2.8, the Pentax is slow to focus. That's only an issue since I'm trying to shoot baseball and I'm not good enough to manual focus sports.

Just wondering if this is normal. Otherwise, the lens seems to be fine and it does take good photos.
I own the same lens. Shooting with K3, KP and K1 II I never found it slow to focus..
02-15-2020, 04:31 PM   #3
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QuoteOriginally posted by Haenzel Quote
I own the same lens. Shooting with K3, KP and K1 II I never found it slow to focus..
K3 II here. Didn't notice slow until a basketball game. What do you shoot?



---------- Post added 02-16-20 at 12:27 AM ----------

I should clarify a little. By slow, it feels like it's moving 50% slower than the other lenses. No scientific testing. But it doesn't hunt like the Tamron does on occasion so that's a good thing. And I think the Pentax is quieter.
02-15-2020, 08:43 PM - 1 Like   #4
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Everything is subjective but I've not found the 24-70 to be slow compared to other Pentax lens. On the contrary it is much faster than (for example) the DA 60-250, DA 300, DA 16-50.

02-16-2020, 01:07 AM   #5
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I do find it slower than primes but as Jatrax says, everything is relative and it’s still much faster to focus than the 16-50. Also agree it rarely hunts, even in low light.
02-16-2020, 01:12 AM   #6
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QuoteOriginally posted by jspi Quote
I see 2 spots on the glass but neither have appeared in any image.
You see two spots of dust behind the front element I suppose.
After a couple of year of use, there were two dust spots visible from the front of the lens. I unscrewed the front group and the dust was just behind, blew so air and mounted the front goup again.
AF motor is slow of that 24-70 f2/8 Tamron, it is so for Nikon and Canon mount, it's by design.

QuoteOriginally posted by jatrax Quote
Everything is subjective but I've not found the 24-70 to be slow compared to other Pentax lens
The Pentax DFA24-70 is the slowest to focus lens compared to the Pentax DFA28-105 and all other DFA lens in the FF lineup.
The DFA24-70 is only a little faster than SDM lenses such as DA*16-50 SDM, DA*50-135 SDM, DA*60-250 SDM or DA*300 SDM.

---------- Post added 16-02-20 at 09:14 ----------

QuoteOriginally posted by jatrax Quote
On the contrary it is much faster than (for example) the DA 60-250, DA 300, DA 16-50.
My impression, feeling, is it's not much faster. I'd say a little faster. In english, if I'm not wrong, "much" mean "a lot", like 50% or 100% faster is much faster, but 10% faster would be a little faster , in my opinion.

Last edited by biz-engineer; 02-16-2020 at 02:04 AM.
02-16-2020, 08:45 AM   #7
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QuoteOriginally posted by biz-engineer Quote
My impression, feeling, is it's not much faster.
Odd. My impression is quite different. I was impressed with the focus speed of the DFA 24-70 especially compared to the DA*16-50. But all things are subjective.

QuoteOriginally posted by biz-engineer Quote
The Pentax DFA24-70 is the slowest to focus lens compared to the Pentax DFA28-105
I've not tested precisely but I would agree the DFA 28-105 seems somewhat faster.
02-16-2020, 11:04 AM   #8
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QuoteOriginally posted by jatrax Quote
Everything is subjective but I've not found the 24-70 to be slow compared to other Pentax lens. On the contrary it is much faster than (for example) the DA 60-250, DA 300, DA 16-50.
The only other Pentax lens I own is the smc Pentax-FA 1:1.4 50mm (only used when needing better than 2.8) so my comparison is to Sigma and Tamron. The Sigma 17-50 f2.8 is the fastest to focus largely because the Tamron 70-200mm f2.8 likes to hunt (it's fast to focus when it doesn't hunt).

From the comments, I don't think I got a bad lens but maybe I should have done a little more research. Since I had a gap from 50-70mm in my kit, it's a good addition so I have 17-200mm covered at f2.8. Then a Sigma 150-500mm for anything beyond 200mm but that's a beast to carry.



02-16-2020, 11:17 AM   #9
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I personally don’t think my 24-70 is slow and I don’t think my 28-105 is faster. None of them comes close to my fastest* screw drive lenses on K-1 though.


* F70-210, FA*80-200/2.8, FA*300/4.5
02-16-2020, 11:58 AM   #10
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QuoteOriginally posted by jspi Quote
Compared to the Tamron 70-200mm f2.8 and Sigma 18-50mm f2.8, the Pentax is slow to focus.
Just wondering if this is normal.
Did you fully charge the battery of your camera before using the FA* 24-70mm ?
02-16-2020, 12:10 PM   #11
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QuoteOriginally posted by angerdan Quote
Did you fully charge the battery of your camera before using the FA* 24-70mm ?
Yes, both the one in the camera body and the grip. After the games, the battery indicator was showing 2/3 remaining. I've never noticed AF speed changing with battery level but I also never thought about it. My shots in the men's games (second game) are usually better. More due to me since I only shoot basketball 3-4 days a year and it takes most of a game to get back into it.

02-16-2020, 01:30 PM   #12
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I have both the DFA28-105 and the DFA24-70, the DFA28-105 is definitely faster. The DFA24-70 is rather slow, that's normal.
03-20-2020, 12:56 AM   #13
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I have the 28-105 and 24-70 Pentax lenses. I don't find them slow to focus at all with my K1. Same thing with my DF A 100 Macro WE F 2.8. They all AF very quickly...so much so that I find the subject in focus before I have time to think about it. Point at the subject, hit the shutter button....bang...the subject is in focus.

I do not find AF an issue at all with my K1 body and these three lenses...the lenses I generally use with my K1.

Of course, there will always be some variance in performance, build quality is any manufactured product...some work better than others, even with the same item, but maybe I just got lucky with the equipment I've discussed..
03-20-2020, 03:06 AM   #14
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I think my copy is pretty fast to focus. Of course, I'm not shooting sports with it, but it seems OK.
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