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05-07-2009, 06:10 PM   #256
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QuoteOriginally posted by ManuH Quote
Pentax AF-C can also be made slightly faster if one is using the central point only. When using the auto-points it's slower. That may confirm the weak non-dedicated to AF CPU theory.
Is it confirmed that Pentax do not currently use a dedicated focus processing CPU?

05-07-2009, 06:49 PM   #257
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QuoteOriginally posted by ManuH Quote
And lens AF speed (SDM or screw). BTW speaking of the lenses the in-lens stabilsation also favors AF speed: the image is stabilised so there is less work for the AF sensors.

Pentax AF-C can also be made slightly faster if one is using the central point only. When using the auto-points it's slower. That may confirm the weak non-dedicated to AF CPU theory.
I had that included in an earlier post, but yeah lenses plays an important part of it.
And to add to the confusion the one being the fastest to aquire focus, may not be the best at tracking a moving subject
05-07-2009, 06:51 PM   #258
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QuoteOriginally posted by distudio Quote
Is it confirmed that Pentax do not currently use a dedicated focus processing CPU?
Hi Rob,
No I do not think there is an official word on it, at least I have not heard any, but steves observations, mentioned earlier in this thread seems to support the theory.
05-07-2009, 06:54 PM   #259
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QuoteOriginally posted by distudio Quote
Is it confirmed that Pentax do not currently use a dedicated focus processing CPU?
No, but if they are its sharing resources with the main CPU because in AFC mode it cannot manage anything like 3fps even oif you are not moving, and in single shot mode there is a notable delay after the shot is taken before AF "gets going" again. On a Canon 1D mk2, there is no such delay and shooting speed in Servo mode seems unaffected.

None of this is proof, of course. But it seemed interesting.


Last edited by *isteve; 05-07-2009 at 07:05 PM.
05-07-2009, 07:36 PM   #260
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QuoteOriginally posted by *isteve Quote
No, but if they are its sharing resources with the main CPU because in AFC mode it cannot manage anything like 3fps even oif you are not moving, and in single shot mode there is a notable delay after the shot is taken before AF "gets going" again.
But in the past, film cameras could focus rather fast and certainly the processors were not as powerful as today. Is there so much calculations anyway? Maybe in a true tracking system but certainly not in the current implentation of Pentax AF-C.
And I don't seem to notice any AF delay after a shot is taken on my K20D. But it's true that in AF-C you rarely get the full 3fps (makes me wonder if a 5fps+ Pentax would be such a good idea anyway).
05-07-2009, 07:46 PM   #261
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QuoteOriginally posted by ManuH Quote
But in the past, film cameras could focus rather fast and certainly the processors were not as powerful as today. Is there so much calculations anyway? Maybe in a true tracking system but certainly not in the current implentation of Pentax AF-C.
No, but the only two CPUs were for the metering system and the AF system and they were largely independent.

Modern SLRs have a central CPU and a considerable amounbt of software controlling everything from menus to WB correction, noise control, Bayer interpolation etc.

If the same CPU is being used for all functions - or the system bus is being shared - then this would seem like a good reason why SLRs dont seem as fast as some of the old film bodies.

QuoteQuote:
And I don't seem to notice any AF delay after a shot is taken on my K20D. But it's true that in AF-C you rarely get the full 3fps (makes me wonder if a 5fps+ Pentax would be such a good idea anyway).
If you set the camera in AFC mode and single shot mode, pick an object about 20 feet away and walk towards it noting the rate at which the focus adjusts (on an SDM lens like the 16-50 its quite fast). Now repeat but take a shot half way. I could swear the adjustments pause or slow down temporarily.
05-08-2009, 02:35 AM   #262
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QuoteOriginally posted by ManuH Quote
And I don't seem to notice any AF delay after a shot is taken on my K20D.
You will see that when you do AF-C & burst with moving subject. The worst case is AF-C, burst & fast moving subject in changing lighting condition. The worst case means your subject is gone without you taking even one shot.



QuoteQuote:

But it's true that in AF-C you rarely get the full 3fps (makes me wonder if a 5fps+ Pentax would be such a good idea anyway).
Yes. You get the full 3fps even in AF-c & burst when you shoot stationary subject.

The best I can do with AF-C & burst was 1 fps with DA200mm & K20D in

Actions shots DA200mm - Photo.net Pentax Forum


I can only get 3fps for moving subject with full manual focus and exposure. That I am afraid is like a theoretical fastest speed of Corolla at 140 mph


Daniel
05-08-2009, 05:39 AM   #263
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QuoteOriginally posted by *isteve Quote
If you set the camera in AFC mode and single shot mode, pick an object about 20 feet away and walk towards it noting the rate at which the focus adjusts (on an SDM lens like the 16-50 its quite fast). Now repeat but take a shot half way. I could swear the adjustments pause or slow down temporarily.
QuoteOriginally posted by danielchtong Quote
You will see that when you do AF-C & burst with moving subject. The worst case is AF-C, burst & fast moving subject in changing lighting condition. The worst case means your subject is gone without you taking even one shot.
I know that AF-C in burst mode, the camera will sometimes pause between the shots but I always thought it was to adjust the focus. And with a screwdrive lens you can hear the noise during this pause. At least the K20D tries to get each shot in focus, my K10D seemed to not care if the shot was in focus or not in a burst.

If like you say it's processor dependent, then there is some hope for improvements because they get faster all the time and it doesn't cost a lot of R&D (for those who will buy the chip).

05-08-2009, 05:53 AM   #264
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Slow AF speed gives you time to think. For me, I have never given that a socond thought. Its a Pentax, it is good enough for me, as there is no other option. Then again, it seem to me that the press are allways looking to a way to bring the Pentax reputation down.

Which you cant do. You just cant.
05-09-2009, 04:26 AM   #265
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QuoteOriginally posted by ManuH Quote
I know that AF-C in burst mode, the camera will sometimes pause between the shots but I always thought it was to adjust the focus.

If like you say it's processor dependent, then there is some hope for improvements because they get faster all the time and it doesn't cost a lot of R&D (for those who will buy the chip).

Here is some suggested recipe for improving AF of any Pentax without hoping for the next AF revolution. And I mean now.

Instead of auto, shoot manual exposure , fixed iso 800 and spot focus.

In shooting kids running around in not quite contracting lighting situation, the fact that shooting in M mode will shave a split second from the hunting time.

I think we are heading back to the main subject line.

Or alternatively, go for the more expensive route of 1Ds or D3x. And do not even think Pentax will remain in present Pentax pricing if it reaches 1Ds or D3x performance parameter. That is a business world


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05-09-2009, 07:51 AM   #266
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QuoteOriginally posted by danielchtong Quote
Here is some suggested recipe for improving AF of any Pentax without hoping for the next AF revolution. And I mean now.

Instead of auto, shoot manual exposure , fixed iso 800 and spot focus.

In shooting kids running around in not quite contracting lighting situation, the fact that shooting in M mode will shave a split second from the hunting time.

I think we are heading back to the main subject line.
Good advise Daniel.

QuoteOriginally posted by danielchtong Quote
Or alternatively, go for the more expensive route of 1Ds or D3x. And do not even think Pentax will remain in present Pentax pricing if it reaches 1Ds or D3x performance parameter. That is a business world


Daniel
Well I do not think anybody here, or at least I am not, expecting them to reach that level. Or if they do stay at the current pricepoint.
II can only speak for my self, but I have never been dissatisfied with the pentax system, given its price/performance ratio, quite the opposite in fact, otherwise I would not run it alongside my nikon system.
05-09-2009, 08:42 AM   #267
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QuoteOriginally posted by Howard Quote
Slow AF speed gives you time to think.
I prefer to do my thinking before I push the button. After that, it's the camera's turn to think.
05-09-2009, 02:18 PM   #268
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QuoteOriginally posted by Wheatfield Quote
I prefer to do my thinking before I push the button. After that, it's the camera's turn to think.
Otherwise you may as well simply manual focus ;-)
05-09-2009, 05:51 PM   #269
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QuoteOriginally posted by danielchtong Quote
Here is some suggested recipe for improving AF of any Pentax without hoping for the next AF revolution. And I mean now.

Instead of auto, shoot manual exposure , fixed iso 800 and spot focus.

In shooting kids running around in not quite contracting lighting situation, the fact that shooting in M mode will shave a split second from the hunting time.
Interesting. Is it something you tested yourself? ISO 800 may not be quite a good idea if we want to save CPU cycles as some say that some NR occurs at 800 and above (on the K10D, K200D, K-m).
05-09-2009, 06:41 PM   #270
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QuoteOriginally posted by Howard Quote
Slow AF speed gives you time to think.
Now we've wandered into the realm where I can't tell if it's sarcasm or not...
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