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05-24-2009, 11:56 AM   #1
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K-7 Low Light AF improvements...

apparently they have increased the speeds SIGNIFICANTLY, if this post from another forum is true:

"... the AF is far faster in low light...

--
Mike from Canada "

He works at a camera store, and the rep let him try it for quite a while. He aso said it makes the K20D seem slow and clunky in pretty much every performance parameter.

Neato...

They were listening....and I'm a Pentax loyalist, even through the dark days 2000-3.


Cheers,
Cameron

05-24-2009, 12:21 PM   #2
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Its accuracy that I'm looking for. Along with the SR, and high ISO noise improvements we'll have ourselves a nice low light shooting rig.
05-24-2009, 03:24 PM   #3
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QuoteOriginally posted by Slugger Quote
Its accuracy that I'm looking for. Along with the SR, and high ISO noise improvements we'll have ourselves a nice low light shooting rig.
Has there been a problem with Accuracy? I've always heard said on the forums and my experience is that the issue with SAFOX being slower than other camera's systems is out weighed by it getting a lot more in focus 'keepers' that other 'faster' systems?
05-24-2009, 05:31 PM   #4
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QuoteOriginally posted by Cambo Quote
apparently they have increased the speeds SIGNIFICANTLY, if this post from another forum is true:

"... the AF is far faster in low light...

--
Mike from Canada "

He works at a camera store, and the rep let him try it for quite a while. He aso said it makes the K20D seem slow and clunky in pretty much every performance parameter.
That's MightyMike on these forums, and he already posted similar findings here. We both tried out the K-7 for quite a while at the Pentax Booth at the Imaging Expo here in Toronto this weekend. A bunch of other forum members were there as well and I think we tried almost every lens they had, and compared against both the K-m and the K20D in focus tests. The K-7 could lock on the black-on-black painted beams against the dark exhibition hall ceiling under almost "no light" conditions which my K20D would just hunt forever on. So it is not just *faster* but can lock on things even the demo D300 on the other side of the expo hall (tethered to a table!) simply could not.

However, even with a lot less "hunting" in general, the Pentax SDM lenses weren't any faster on the K-7 (I tried my own 50-135 to be consistent). Compared to Canon L-series USM (a ring motor around the lens focus element), the Pentax SDM (a drive motor in line with the screw shaft) is almost glacial on heavy zooms, so the AF system still has to wait for the elements to moved into the right places. But put a screw-drive DA limited prime on there and *bang* the K-7 is focused almost instantly.

Not sure about the "accuracy" since the SD card doors were quite securely taped shut and the image would only pop up on the (gorgeous) 3" screen for a second... but I'll assume the same as my K20D, which is quite accurate with good glass.

05-24-2009, 07:02 PM   #5
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QuoteOriginally posted by panoguy Quote

the Pentax SDM lenses weren't any faster on the K-7 (I tried my own 50-135 to be consistent). Compared to Canon L-series USM (a ring motor around the lens focus element), the Pentax SDM (a drive motor in line with the screw shaft) is almost glacial on heavy zooms, so the AF system still has to wait for the elements to moved into the right places.
This is what I have been shouting to the rooftops, and your test has confirmed. The lenses with SDM are lens-motor limited in AF, not body limited! I'll bet one reason why people complain about the k20d AF is because they are focusing with an SDM lens on it. Honestly, the only time I ever complain about AF on my k20d is when a SDM lens (I have had 5) is attached.

I'll hold out on any more SDM lens purchases, until generation II SDM (if it ever happens) Please, Pentax, let us choose screw drive over SDM in firmware!

Thanks for the feedback!

Last edited by PentaxPoke; 05-24-2009 at 07:14 PM.
05-24-2009, 07:52 PM   #6
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I've found the same to be true of the Sigma lens that I have. The 50mm prime will lock on in low light however the Sigma lens will hunt and hunt and then still not find a sharp focus.
05-24-2009, 08:31 PM   #7
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QuoteOriginally posted by PentaxPoke Quote
This is what I have been shouting to the rooftops, and your test has confirmed. The lenses with SDM are lens-motor limited in AF, not body limited!
Confirmed? Be aware that this is only 0.20 firmware.
Even though the motor is in the lens, it does not mean the speed is not body limited. I am not sure how much power the motor was rated, or whether it is already maxed out in K20D, but it is certainly possible that it can go faster with higher power input.
05-24-2009, 09:38 PM   #8
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QuoteOriginally posted by nosnoop Quote
Confirmed? Be aware that this is only 0.20 firmware.
Even though the motor is in the lens, it does not mean the speed is not body limited. I am not sure how much power the motor was rated, or whether it is already maxed out in K20D, but it is certainly possible that it can go faster with higher power input.
I really doubt that firmware changes will result in higher torque and rpm to the SDM micromotors. I'm confident that the Pentax engineers designed the k20d to deliver the rated power to the SDM motors.

05-24-2009, 10:25 PM   #9
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QuoteOriginally posted by PentaxPoke Quote
I really doubt that firmware changes will result in higher torque and rpm to the SDM micromotors. I'm confident that the Pentax engineers designed the k20d to deliver the rated power to the SDM motors.
The limitations could be in the K10/20 AF processing chip, if it cant handle more than "x" percent of possible SDM lens speed, then thats a real limitation of the body. There were someone at MightyMike´s "I tested the K-7" thread on dpr had tested K-7 with 50-135 claiming AF was significantly faster on the K-7. I suppose that there will be more info on this he coming weeks.

/Mats
05-24-2009, 10:28 PM   #10
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QuoteOriginally posted by Cambo Quote

He aso said it makes the K20D seem slow and clunky in pretty much every performance parameter.
the k2000 makes the k20 look slow as well. So...........
05-24-2009, 11:53 PM   #11
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QuoteOriginally posted by PentaxPoke Quote
This is what I have been shouting to the rooftops, and your test has confirmed. The lenses with SDM are lens-motor limited in AF, not body limited! I'll bet one reason why people complain about the k20d AF is because they are focusing with an SDM lens on it. Honestly, the only time I ever complain about AF on my k20d is when a SDM lens (I have had 5) is attached.

I'll hold out on any more SDM lens purchases, until generation II SDM (if it ever happens) Please, Pentax, let us choose screw drive over SDM in firmware!

Thanks for the feedback!
Watch the videos in my sig. 17-70 SDM is as fast as 16-45. The only slow--in terms of hunting--SDM lenses are 50-135 and 55.

DA 40 f/2.8, albeit a fast AF-wise lens, becomes SLOW under low light, with the old AF system.
05-25-2009, 12:34 AM   #12
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QuoteOriginally posted by asdf Quote
Watch the videos in my sig. 17-70 SDM is as fast as 16-45. The only slow--in terms of hunting--SDM lenses are 50-135 and 55.

DA 40 f/2.8, albeit a fast AF-wise lens, becomes SLOW under low light, with the old AF system.
Actually, I am not talking about hunting. My complaint is with how slow the focus ring moves on SDM. Compare that in your videos. I think your videos show how slow the SDM moves compared to screw drive lenses. I agree that hunting is most likely an AF algorithm issue.
05-25-2009, 12:47 AM   #13
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QuoteOriginally posted by PentaxPoke Quote
Actually, I am not talking about hunting. My complaint is with how slow the focus ring moves on SDM. Compare that in your videos. I think your videos show how slow the SDM moves compared to screw drive lenses. I agree that hunting is most likely an AF algorithm issue.
In some cases.

Watch the 300 f/4 video. On a DS, the screw motor is MUCH slower vs SDM on K20D.

BTW, the videos in the playlist are not mine.

I was also talking about the lock-on time. It takes a longer while for DA 40 f/2.8 or any other lens to lock on under low light--without actually hunting.
05-25-2009, 12:53 AM   #14
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QuoteOriginally posted by PentaxPoke Quote
Actually, I am not talking about hunting. My complaint is with how slow the focus ring moves on SDM. Compare that in your videos. I think your videos show how slow the SDM moves compared to screw drive lenses. I agree that hunting is most likely an AF algorithm issue.
Don't the SDM lenses have a longer throw, anyway? Curious how you could film a focusing ring and derive conclusions.

I thought half the point of the DAs was if you don't like the focus, you can just focus? How do you videotape that?

Still not gettingit. If someone's paying me to point a camera at something faster than I can tell it to focus, *they* can shell out for the gear. Guess they call that 'pro.' these days.
05-25-2009, 12:55 AM   #15
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QuoteOriginally posted by Ratmagiclady Quote
Don't the SDM lenses have a longer throw, anyway?
Some of them. Not all SDM/HSM lenses are the same. Some are slow, some are fast, etc. 50-135 seems to be a popular lens and it's slow--hence, the general perception that SDM is slow.
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