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09-09-2017, 04:55 AM   #1
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Is the moving sensor slowing autofocus????

SR - you know...

Is that the one thing slowing Pentax autofocus.

I just think - you elaborate!

Is in camera shake reduction a dead end?

Awaits fire...


Last edited by Gutta Perka; 09-09-2017 at 05:01 AM.
09-09-2017, 05:15 AM - 5 Likes   #2
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It doesn't affect AF the way you are suggesting. Even when IBIS it is switched off, it still needs time to spool up and hold the sensor where it is supposed to be. Among the cameras I work with, in manual focus mode the shutter lag on Pentax cameras are the slowest. And this lag makes Pentax cameras seem slower to work with. Being slower to work with isn't inherently a bad thing - I know a few photographers who would benefit from a more contemplative style of working, and actually considering what they are shooting instead of having their cameras fapping away at 11 fps.

But I wouldn't go so far as to suggest it is a dead end, it certainly has proved very useful in achieving things that optical stabilization systems could not accomplish, the Astrotracer for instance.


*brings marshmallows for the flamefest*

Last edited by Digitalis; 09-09-2017 at 06:00 AM.
09-09-2017, 05:29 AM - 3 Likes   #3
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QuoteOriginally posted by Digitalis Quote
having their cameras fapping away
heh
09-09-2017, 05:46 AM   #4
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QuoteOriginally posted by Gutta Perka Quote
SR - you know...

Is that the one thing slowing Pentax autofocus.

I just think - you elaborate!

Is in camera shake reduction a dead end?

Awaits fire...
There is a discussion about this on another forum at the moment.

But I would turn the question back on you..... what aspect of your photography is being hampered by this perceived slow autofocus?

I don't find the AF slow at all.

09-09-2017, 05:59 AM   #5
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QuoteOriginally posted by pschlute Quote
There is a discussion about this on another forum at the moment.

But I would turn the question back on you..... what aspect of your photography is being hampered by this perceived slow autofocus?

I don't find the AF slow at all.
Heard of "hunting" ?
09-09-2017, 06:07 AM - 5 Likes   #6
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I cannot for the life of me wrap my head around this line of thought. Where does this idea come from? Did some FUD piece on a blog go viral or something?

Consider the autofocusing SLR design: the main mirror obstructs the film/sensor and reflects the projected image up into the pentaprism viewfinder, where some of it is diverted to the metering sensor. Some light bleeds through a half-silvered area of the main mirror and is reflected down onto the AF sensor by a small secondary mirror behind the primary.

Nowhere in this process does the film or image sensor play any role in focusing. IBIS does not, and indeed cannot, affect the AF sensor in any way. The AF sensor does not move.

In-lens stabilisation may help AF performance if the camera is shaking severely by steadying the image projected onto the AF sensor, but this does not make IBIS inherently detrimental to AF performance.

In live view, IBIS can be expected to improve AF performance by helping project a steady, high-contrast image with no motion blur onto the image sensor which is now also tasked with metering and AF.

Last edited by Jens Lyn IV; 09-09-2017 at 06:16 AM.
09-09-2017, 06:08 AM - 4 Likes   #7
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The auto focus module is at a different location from the sensor and the sensor moving shouldn't affect it (it might effect live view/contrast AF, but not PDAF). Hunting is usually the result of the photographer choosing an area with little to no contrast to focus on. All camera systems struggle with that.

From my perspective the "issues" Pentax has with auto focus have more to do with tracking. AF-S works well and is very sure until you get down to very low light levels. Tracking is often limited by lenses and more recent DFA lenses seem to do better keeping up with movement.

So, the answer is "No."
09-09-2017, 06:33 AM   #8
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QuoteOriginally posted by Rondec Quote
The auto focus module is at a different location from the sensor and the sensor moving shouldn't affect it (it might effect live view/contrast AF, but not PDAF). Hunting is usually the result of the photographer choosing an area with little to no contrast to focus on. All camera systems struggle with that.

From my perspective the "issues" Pentax has with auto focus have more to do with tracking. AF-S works well and is very sure until you get down to very low light levels. Tracking is often limited by lenses and more recent DFA lenses seem to do better keeping up with movement.

So, the answer is "No."
My Pentax's K5IIs, K3, K1 are hunting more than my other brand cameras. That's it!

09-09-2017, 06:55 AM - 3 Likes   #9
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QuoteOriginally posted by Gutta Perka Quote
Is in camera shake reduction a dead end?
No it is not. Everybody is using it except Nikon and Canon (Fuji will join in soon according to rumors). It has very little to do with AF speed and nothing with pdaf. Pentax AF response is very fast. AF tracking is just not as sophisticated as with other brands and Pentax doesn't have very many lenses that can properly use it. The SR-AF speed issue is FUD from troll city.
09-09-2017, 07:05 AM   #10
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QuoteOriginally posted by Digitalis Quote
It doesn't affect AF the way you are suggesting. Even when IBIS it is switched off, it still needs time to spool up and hold the sensor where it is supposed to be. Among the cameras I work with, in manual focus mode the shutter lag on Pentax cameras are the slowest. And this lag makes Pentax cameras seem slower to work with. Being slower to work with isn't inherently a bad thing - I know a few photographers who would benefit from a more contemplative style of working, and actually considering what they are shooting instead of having their cameras fapping away at 11 fps.

But I wouldn't go so far as to suggest it is a dead end, it certainly has proved very useful in achieving things that optical stabilization systems could not accomplish, the Astrotracer for instance.


*brings marshmallows for the flamefest*
QuoteOriginally posted by Digitalis Quote
I know a few photographers who would benefit from a more contemplative style of working, and actually considering what they are shooting instead of having their cameras fapping away at 11 fps.
Call Canikon and tell them to slow down - Their cameras focus to fast and to produce the same with the suffix "-slow" for the arts sake! Tell them to look at THE PENTAX relaxed style!.

(OK - I'm pretty happy with my latest K1-Pentax and know how to use it)
09-09-2017, 07:07 AM   #11
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I think the previous responses have laid the suggestion to rest but I thought I would add that the Sony A9 uses IBIS and it is an extremely fast and accurate focusing camera. It is unlikely that IBIS alone has any impact on focus speed. In any case, Pentax K-1 is really not that slow as numerous pictures on the site demonstrate.
09-09-2017, 07:19 AM   #12
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QuoteOriginally posted by Gutta Perka Quote
Heard of "hunting" ?
I have. But I don't see it with my K1 unless I point it at a contrast-less scene.
09-09-2017, 07:33 AM   #13
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QuoteOriginally posted by Jens Lyn IV Quote
Nowhere in this process does the film or image sensor play any role in focusing. IBIS does not, and indeed cannot, affect the AF sensor in any way. The AF sensor does not move.
The AF sensor does not move, this is an empirical fact. But the Sensor does, quite a bit actually. The IBIS system needs to spool up whether you are using it to stabilize a shot or not, this process introduces lag, which is compounded by AF lag*. And all this has to happen before the mirror has even flipped up and the first curtain gets moving.

* which depends on the lens, its fastest aperture, focal length, type of AF drive, subject magnification etc etc so on, and so forth.
09-09-2017, 08:55 AM   #14
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QuoteOriginally posted by Digitalis Quote
* which depends on the lens, its fastest aperture, focal length, type of AF drive, subject magnification etc etc so on, and so forth.
....and camera brand used!

(But there are are other things to enjoy - K1 is cheap.....)

---------- Post added 09-09-17 at 06:02 PM ----------

About heard of hunting...
QuoteOriginally posted by pschlute Quote
I have. But I don't see it with my K1 unless I point it at a contrast-less scene.
You are happy - here we have those often interesting scenes.
I don't think You bought the K1 for just high contrast scenes .... or?

(However: "Blessed are the meek ones.")

Last edited by Gutta Perka; 09-09-2017 at 09:24 AM.
09-09-2017, 11:07 AM   #15
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QuoteOriginally posted by Digitalis Quote
The IBIS system needs to spool up whether you are using it to stabilize a shot or not, this process introduces lag, which is compounded by AF lag*.
This is true, but now we're talking about overall shutter lag. The original question was whether IBIS slows AF. If, instead, we ask whether IBIS slows down shooting, as you've mentioned, the answer depends on whether the sensor assembly is already 'primed'. In certain cases, it won't be.
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