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03-14-2018, 08:59 AM   #1
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AF on 24-70

Hi Folks,
I have the K-1 and the FA Limited lenses. I love to shoot close to wide open with them, but I do find that the af hunts a little and struggles to lock on. I use the single point af setting. Is this just the nature of the lenses, or is it the af system? I am thinking about getting the 24-70 to use on vacation, and just wondered if the AF is better on the modern zooms. Thank you.
Terry

03-14-2018, 09:09 AM   #2
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AF on the FA Limited lenses is screwdrive, driven by a motor in the camera. AF in modern lenses like the DFA 24-70 is using a motor in the lens. I have found the DFA 24-70 to be faster and more precise than my screwdrive lenses.
However, hunting is more likely an issue with low light or low contrast in the subject. I don't notice much hunting with the 24-70 and I'm quite happy with the AF performance. I cannot say whether it is better than the FA Limited as the only way to tell would be to shoot them side by side under the same conditions.
03-14-2018, 09:43 AM   #3
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QuoteOriginally posted by jatrax Quote
AF on the FA Limited lenses is screwdrive, driven by a motor in the camera. AF in modern lenses like the DFA 24-70 is using a motor in the lens. I have found the DFA 24-70 to be faster and more precise than my screwdrive lenses.
However, hunting is more likely an issue with low light or low contrast in the subject. I don't notice much hunting with the 24-70 and I'm quite happy with the AF performance. I cannot say whether it is better than the FA Limited as the only way to tell would be to shoot them side by side under the same conditions.
Thank you very much. That is exactly what I needed to know.
Terry
03-14-2018, 09:46 AM   #4
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Perhaps your 31mm has a calibration issue? Or, maybe switch to using a few extra AF points in the center, in case there's low contrast as jatrax mentioned.


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03-14-2018, 11:35 AM   #5
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QuoteOriginally posted by TerryL Quote
Hi Folks,
I have the K-1 and the FA Limited lenses. I love to shoot close to wide open with them, but I do find that the af hunts a little and struggles to lock on. I use the single point af setting. Is this just the nature of the lenses, or is it the af system? I am thinking about getting the 24-70 to use on vacation, and just wondered if the AF is better on the modern zooms. Thank you.
Terry
It has a ring type ultrasonic motor on it so it should be faster and more precise.
The other thing to do is use back button AF so the camera doesn’t try to reconfirm focus every time you take a photo. It also means you can focus and recompose easy, which is require when using fast apertures as only the centre 3 points are rated to F2.8 and colour sensitive vs F5.6 for the rest. Just use the centre point and forget about the rest for fast aperture/low light work.
03-14-2018, 02:10 PM   #6
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I have the K-1, 24-70 and some FA Limiteds (43, 77). I also use single point select AF, with back button AF and shutter half-press AF disabled. This is what I can say from my own practical experience (please note I didn't bother to try and calibrate anything, I just mount the lens and shoot away):

- the FA Limiteds AF is improved when mounted on the K-1 as compared to the K5IIs. Maybe not faster, but better percentage of in-focus pictures;
- The DFA 24-70mm has definitively faster AF as compared to the Limiteds, no question about it. The Limiteds are ok, but they tend to hunt a little bit and lose time, especially in low light;
- The DFA 24-70mm is not perfect... in a weird way. Sometimes I shoot events in places with bad light (bars, clubs, concerts etc) and I get close to 100% pictures in focus. I am amazed. Next day it misses focus in broad daylight for no obvious reasons, with static subject. So what gives?

Overall I would say 1) K-1 is a huge improvement as compared to K5IIs regarding any lens and 2) 24-70 is definitively faster, and I would also say more precise if not for some weird misses from time to time. Maybe calibration can help? I really don't care about it, I'm not a professional photographer and most of my shots are landscapes or some other type of static shots where I can use contrast AF in live view.
03-14-2018, 02:19 PM   #7
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QuoteOriginally posted by Adam Quote
Perhaps your 31mm has a calibration issue? Or, maybe switch to using a few extra AF points in the center, in case there's low contrast as jatrax mentioned.
Hi Adam,
I'll try that. I do like using single point and putting the focus exactly where I want it. Especially when using fast lenses.
Terry[COLOR="Silver"]

---------- Post added 03-14-18 at 02:40 PM ----------

QuoteOriginally posted by Hattifnatt Quote
I have the K-1, 24-70 and some FA Limiteds (43, 77). I also use single point select AF, with back button AF and shutter half-press AF disabled. This is what I can say from my own practical experience (please note I didn't bother to try and calibrate anything, I just mount the lens and shoot away):

- the FA Limiteds AF is improved when mounted on the K-1 as compared to the K5IIs. Maybe not faster, but better percentage of in-focus pictures;
- The DFA 24-70mm has definitively faster AF as compared to the Limiteds, no question about it. The Limiteds are ok, but they tend to hunt a little bit and lose time, especially in low light;
- The DFA 24-70mm is not perfect... in a weird way. Sometimes I shoot events in places with bad light (bars, clubs, concerts etc) and I get close to 100% pictures in focus. I am amazed. Next day it misses focus in broad daylight for no obvious reasons, with static subject. So what gives?

Overall I would say 1) K-1 is a huge improvement as compared to K5IIs regarding any lens and 2) 24-70 is definitively faster, and I would also say more precise if not for some weird misses from time to time. Maybe calibration can help? I really don't care about it, I'm not a professional photographer and most of my shots are landscapes or some other type of static shots where I can use contrast AF in live view.
Thank you for the reply. Can you please explain what back button focus means?
Thank you.
Terry

Last edited by TerryL; 03-14-2018 at 02:36 PM. Reason: Correct spelling
03-14-2018, 02:51 PM   #8
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QuoteOriginally posted by TerryL Quote
Thank you for the reply. Can you please explain what back button focus means? Thank you.
Basically it means you disable AF when shutter half-pressed and instead AF only when the AF button on the back on your camera is pressed. It may seem weird af first (against your muscle memory), but it has a lot of advantages. I had quite a few beers this evening, so instead of listing them out (which may end up badly) I will just redirect you to some resources:



Maybe you prefer written stuff:

Back Button Focus Explained - What Is It & Why You Need It!

03-14-2018, 03:46 PM   #9
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QuoteOriginally posted by Hattifnatt Quote
Basically it means you disable AF when shutter half-pressed and instead AF only when the AF button on the back on your camera is pressed. It may seem weird af first (against your muscle memory), but it has a lot of advantages. I had quite a few beers this evening, so instead of listing them out (which may end up badly) I will just redirect you to some resources:

What Is Back Button Focus And How To Use It | Q&A Ep.76 - YouTube

Back-Button Focus: Why EVERYONE should use that AF-On autofocus button - YouTube

Maybe you prefer written stuff:

Back Button Focus Explained - What Is It & Why You Need It!
This is excellent. Thank you very much.
Terry
03-14-2018, 04:09 PM   #10
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QuoteOriginally posted by TerryL Quote
Hi Adam,
I'll try that. I do like using single point and putting the focus exactly where I want it. Especially when using fast lenses.
Remember, Terry, you can't put the focus exactly where you want it ... you need to put it on a line.

A line close to exactly where you want it, perhaps.

That's the nature of PDAF.
03-15-2018, 11:59 AM - 1 Like   #11
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QuoteOriginally posted by clackers Quote
Remember, Terry, you can't put the focus exactly where you want it ... you need to put it on a line.

A line close to exactly where you want it, perhaps.

That's the nature of PDAF.
Thank you Clackers. I looked at your pictures, last night. Amazing work, I really enjoyed them.
Terry
03-16-2018, 12:58 PM   #12
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QuoteOriginally posted by TerryL Quote
Thank you Clackers. I looked at your pictures, last night. Amazing work, I really enjoyed them.
Terry
Thanks, Terry, I enjoy giving all styles a go - I see you're into drones, I'm going to try a Spark later in the year.
03-17-2018, 07:49 AM   #13
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QuoteOriginally posted by clackers Quote
Thanks, Terry, I enjoy giving all styles a go - I see you're into drones, I'm going to try a Spark later in the year.
I like the Spark, but prefer the Phantom 4 Pro. It has the 1" sensor in the camera, and a stronger receiver. It was a home run for DJI. The Spark is fine, but only in light to no wind, which is rarely the case.
Terry
03-17-2018, 01:04 PM   #14
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QuoteOriginally posted by TerryL Quote
I like the Spark, but prefer the Phantom 4 Pro. It has the 1" sensor in the camera, and a stronger receiver. It was a home run for DJI. The Spark is fine, but only in light to no wind, which is rarely the case.
Terry
Yes, I bought mine to slip into a hiking backpack. Thanks for pointing out what to get if more weight and cost isn't a problem!

03-17-2018, 01:43 PM   #15
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My feeling is that my 100M WR with screw drive AF nails focus better with all my Pentax cameras than any other lens. The focus noise is ugly, the hunting from close to infinity is disturbing sometimes, but this lens is always right on. Maybe I am more careful where I place focus because of the noise and slow focusing. With the new silent AF there is less thinking, less interaction between lens and ear/brain during focusing, so maybe I pay less attention and miss sometimes. 77ltd is hunting in low light, but hunting here means that you hear a noise instead of watching a green light blink in the viewfinder. Re-focus until happy concentrate on the framing.
I am overall happier with fast and silent AF in a modern lens package, but sometimes we should still appreciate old school noisy AF - no zoom option also keeps your attention on correct exposure, focus and framing. Focus with my D-FA 24-70/70-200 is perfectly fine, but different :-)
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