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02-20-2024, 01:10 AM   #1
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K-1/D-FA Lens C-AF Capabilities

Hello everyone,

I'm seeking some insight on how good the AF-C is on the K-1 and the D-FA lenses. I personally shoot on Pentax film cameras most of the time, but from time to time I'll do some professional work, i.e. portraits and weddings, using the K-1 and I'd like to do more of it. So my question is how are the D-FA line of lenses when it comes to continuous autofocusing? Can it reliably hit focus on moving people without focus hunting? Pentax has a pretty limited line of lenses, but the one's I'm eyeing atm are the D-FA 24-70 F2.8 and the D-FA* 50 F1.4 while I currently own the D-FA 100mm Macro and the FA 31mm Lmt.

Or might I have better luck with something like a Nikon D750 for this specific purpose? I just don't like owning cameras I don't use much

Thank you and here's hoping Pentax will release a successor to the K-1 and maybe a couple more lenses *crossing my fingers*


Last edited by Mchubble; 02-21-2024 at 09:56 PM.
02-20-2024, 01:47 AM - 4 Likes   #2
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K-1 and K-1 II coupled with a modern D-FA lens will do continuous AF , including tracking, very well.

The earlier DA lenses, not so good, much slower.

I have used my K-1 + DFA 150-450 for motorsports with well over 90% hit rate.



02-20-2024, 04:22 AM   #3
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QuoteOriginally posted by Mchubble Quote
So my question is how are the D-FA line of lenses when it comes to continuous autofocusing?
It's bad, in my opinion, I'm afraid.

QuoteOriginally posted by Mchubble Quote
Can it reliably hit focus on moving people without focus hunting?
Yes. For this I don't use AF-C tracking in burst mode. I use AF-C with focus priority and single exposure, then I press shutter button fully once the subject is at the place I want it to be in the frame (viewfinder). If I want another shot, I release the shutter button fully, and press the shutter button fully again.
02-20-2024, 05:27 AM   #4
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QuoteOriginally posted by biz-engineer Quote
It's bad, in my opinion, I'm afraid
What lenses are you using Biz ?

02-20-2024, 08:20 AM   #5
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QuoteOriginally posted by pschlute Quote
What lenses are you using Biz ?
DFA150-450, DFA70-200, DFA 70-210, the best lenses. Pretty much 10% to 30% keepers best case when shooting more than 1 picture in a row.
Whereas with single exposure mode, AF-C focus priority, 90% keepers. But that means 1 picture at a time.
AF tracking means you keep the shutter button fully pressed and the camera in burst high mode should track focus of the subject and take pictures when the subject is in focus. e.g 10 consecutive exposures. Is that the mode you are using?
02-20-2024, 09:06 AM - 1 Like   #6
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QuoteOriginally posted by biz-engineer Quote
AF tracking means you keep the shutter button fully pressed and the camera in burst high mode should track focus of the subject and take pictures when the subject is in focus. e.g 10 consecutive exposures. Is that the mode you are using?
Yes, with either the DFA 150-450 or 70-200. I can track my dogs running around the garden, or cars on a track like above, with a keeper rate of over 90%. I am surprised you are not getting way better than 10-30%.

There is an article on here somewhere explaining the best set-up, I will try and fish it out and post a link.

My old DA*60-250 or 300 were hopeless at the same task.
02-20-2024, 09:35 AM   #7
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QuoteOriginally posted by pschlute Quote
Yes, with either the DFA 150-450 or 70-200. I can track my dogs running around the garden, or cars on a track like above, with a keeper rate of over 90%. I am surprised you are not getting way better than 10-30%.
At f/22 I get 90% keepers. At f5.6 , depth of field is half the depth of the subject, what's behind the cars (cars coming at me) is in focus. Focus tracking is always late relative to subject. Normally the focus plane should be at the front half of the cars. And after 11 exposures raw the buffer is full and the memory card writing busy, I have to wait for at least 30 seconds to a minute, and in the meantime more cars have passed.


QuoteOriginally posted by pschlute Quote
There is an article on here somewhere explaining the best set-up, I will try and fish it out and post a link.
I found the best method, it's unbeatable: AF-C 1st frame in focus priority, single shot. I wait for the subject to be right in the frame , I press the shutter fully, I get only one picture and it's in focus most of the times. I stopped using focus tracking with the K1, too much buffering, to many out of focus images to delete. Considering I have one 1 shot to capture the subject, I spend more time scouting the location and pre-visualizing how cars with fit with a nice background, much less pictures, better quality.

Below ~80 Megapixels (reduced) stiched pano of old timer. K1 II + DFA 70-210 @ 210mm f/4 (wide open).



Last edited by biz-engineer; 02-20-2024 at 09:55 AM.
02-20-2024, 12:09 PM - 1 Like   #8
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QuoteOriginally posted by biz-engineer Quote
At f/22 I get 90% keepers. At f5.6 , depth of field is half the depth of the subject
With cars on a track I have used f8 with great success as above.

Here are the articles, hope this helps you.....

Guide to Camera and Autofocus Settings for Shooting Sports - Articles and Tips | PentaxForums.com

DSLR Guide for Shooting Sports II: Horse Racing - Articles and Tips | PentaxForums.com
02-20-2024, 03:34 PM   #9
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QuoteOriginally posted by pschlute Quote
K-1 and K-1 II coupled with a modern D-FA lens will do continuous AF , including tracking, very well.

The earlier DA lenses, not so good, much slower.

I have used my K-1 + DFA 150-450 for motorsports with well over 90% hit rate.



Thank you for the feedback! I guess there's no harm in picking up a lens and seeing how well it autofocuses on people in a dynamic environment.
02-20-2024, 11:29 PM   #10
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QuoteOriginally posted by Mchubble Quote
Thank you for the feedback! I guess there's no harm in picking up a lens and seeing how well it autofocuses on people in a dynamic environment.
Absolutely. For testing, playing with auto-focus, you can pick an object having a repeated motion. Subjects can be cars in some well chosen streets (traffic and speed of cars depends on the street chosen). I used ski lifts as focus object because ski lifts come and go repeatedly at constant speed, so I could take a number of pictures for each setting and compare statistics. Ideally, I would use a bottle factory focusing on bottles moving at constant speed on a conveyor belt.
02-24-2024, 03:32 AM   #11
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QuoteOriginally posted by Mchubble Quote
So my question is how are the D-FA line of lenses when it comes to continuous autofocusing? Can it reliably hit focus on moving people without focus hunting?
Pentax has a pretty limited line of lenses, but the one's I'm eyeing atm are the D-FA 24-70 F2.8 and the D-FA* 50 F1.4

Thank you and here's hoping Pentax will release a successor to the K-1 and maybe a couple more lenses *crossing my fingers*
The HD D-FA lenses with SDM motor are all good.

If you're looking for AF performance, go for the K-3 III with SAFOX XIII.



QuoteOriginally posted by pschlute Quote
K-1 and K-1 II coupled with a modern D-FA lens will do continuous AF , including tracking, very well.
The earlier DA lenses, not so good, much slower.
It's not about lens line (D-FA or DA), only about the AF motor used.
So all lenses with screwdrive from the camera have the lowest capabilities, then follows SDM (old), DC, SDM (new) and finally PLM for the maximum C.AF capability.
02-24-2024, 06:35 PM   #12
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QuoteOriginally posted by angerdan Quote
The HD D-FA lenses with SDM motor are all good.

If you're looking for AF performance, go for the K-3 III with SAFOX XIII.




It's not about lens line (D-FA or DA), only about the AF motor used.
So all lenses with screwdrive from the camera have the lowest capabilities, then follows SDM (old), DC, SDM (new) and finally PLM for the maximum C.AF capability.
Thank you for the response. I've considered getting a K-3 III, but I'm naively holding out hope they'll release a K-1 III within the next year or two. I think I'll probably just pick up the D-FA 24-70 SDM or the D-FA* 50 SDM and see how I get along with it.
02-24-2024, 07:30 PM   #13
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The k3 iii and d-fa* 50mm focuses fast and silent
02-25-2024, 03:08 AM   #14
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QuoteOriginally posted by Mchubble Quote
I've considered getting a K-3 III, but I'm naively holding out hope they'll release a K-1 III within the next year or two.
I think I'll probably just pick up the D-FA 24-70 SDM or the D-FA* 50 SDM and see how I get along with it.
Since there are no official statements yet, i'd expect at least two years waiting time if a K-1 III will be released.
If there would come a K-1 III, it would be in the range of more than $2000.

For K-3 III there already are fast AF lenses.
Lenses with SDM/DC Autofocus | PentaxForums.com
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