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12-18-2008, 05:20 AM   #16
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Correct me if I'm wrong but didn't Popular photography simply use the test results from the K10D - as far as I am aware they never actually tested the K20D.

I seem to remember them being roundly criticised for doing this - the explanation at the time is that Pentax hadn't changed the AF - but a lot of anecdotal evidence seems to suggest the K20D is faster.

Anyway from the graphs I see that the Pentax AF holds its own in bright light but drops off drastically in low light - honestly no big deal to me and my *ist DS suits me just fine still; and with the 360 flash focus assist I have no problems in low light. (And don't give me crap about the extra expense as my camera & flash was a far cheaper option than the base level canikons of the day.)

12-18-2008, 07:48 AM   #17
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I don't know how it compares with Canon or Nikon or even the K20d but I do know that focus speed on the K-m is vastly improved over the K100 especially in low light and seems faster than the similarly priced cameras from the big two.

It seems to me that Pentax is working on it.
12-18-2008, 08:00 AM   #18
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I wonder if the changes are hardware or programming? i.e. the K20D could see updates via a new firmware download.

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12-18-2008, 08:10 AM   #19
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QuoteOriginally posted by lol101 Quote
But are they really?
As I said originally, it was a subjective assessment. I wouldn't want to mislead anyone about the capabilities of the 40D. The focus issues I had were certainly extremely minor overall and always in lower light with a slower lens, but contradictory to your objective findings. However, I didn't experience similar problems with my much less expensive K100. Ultimately, I was lucky enough to have the means to try two separate systems out (Canon and Pentax). While I didn't dive head first into the Canon system, the limitations of the Canon ecosystem (IS USM lenses being expensive, weather sealing only in the highest end cameras, less "in camera" functionality in the enthusiast bodies...) led me to decide to come back to Pentax. These same issues may not be a big deal for others and they would make a different choice. I think its well documented that the Canon and Nikon systems have faster AF performance, larger buffers, better availability of product, more people able to provide guidance and instruction on the products, cheaper accessories, etc. Just wanted to provide input into the thread, definitely not trying to state I have done the rigorous technical analysis necessary to provide a definitive answer. Though, I challenge anyone to show me that there is such a thing.

12-18-2008, 08:26 AM   #20
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I shoot both the K20D and the Canon 1DmkIII.
I have no problem with the "speed" of the focus on the Pentax. The problem is that it is not predictive.

In extremely low light you cannot shoot action anyway. At a wedding I shot last month I got a whole sequence of shots @ ISO 1600 F2.8 1/15sec with a 16-50 lens and had 90% come out in sharp focus. When you're shooting at 1/15 of a second it does not matter if it takes an extra 0.5 sec to get focus because your target better be stationary.

For me the move to Canon was 100% because of the predictive AF not because of focus "speed".

incidentally... of the three Pentax lenses I have right now (300F2.8, 16-50, 50-135) the 50-135 appears to have the weakest AF performance. I find this curious for a number of reasons. Anyone else experience this?
12-18-2008, 11:01 AM   #21
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QuoteOriginally posted by Falcons Quote
Correct me if I'm wrong but didn't Popular photography simply use the test results from the K10D - as far as I am aware they never actually tested the K20D.
I seem to remember them being roundly criticised for doing this - the explanation at the time is that Pentax hadn't changed the AF - but a lot of anecdotal evidence seems to suggest the K20D is faster.
I don't know - be very grateful for references/links to that assertion.

Here's the link to the PopPhoto review Camera Test: Pentax K20D

they do say this:

" Fast AF, accurate metering
Sticking with the K10D's 11-point wide AF system was a good choice. With a 3x3 grid of cross-type sensors surrounded by a linear sensor, the array works with f/5.6 or brighter lenses.
In our Lab tests, the AF was very fast in bright light and sensitive in low light down to EV -1 (though slow by EV 0). In field tests, it tracked rapidly moving objects across a wide area of the frame. But it slows to more than 1 second at EV 1, and is sluggish at EV -1-not as fast nor as sensitive as the AF systems in several Canon, Nikon, and Sony DSLRs. "

which is not the same as saying they just used the K10D AF test figures.

Here's their Camera Test: Pentax K10D

and the AF test results -



the scale on the horizontal (light level) axis is misaligned, they should fall directly under each vertical line on the grid.

Comparing - although they do look similar - there are enough differences at points that it would seem that PopPhoto did NOT just re-use the K10D AF test results.

Last edited by UnknownVT; 12-18-2008 at 11:21 AM.
12-18-2008, 02:34 PM   #22
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QuoteOriginally posted by pentaxmz Quote
With all due respect, are you serious?

With a little more than a second of difference; that's a huge amount of difference. And these tests were done in a controlled studio setting. In real-world conditions, the difference could be even more.

But even one second could be the difference between getting the shot and not!

These graphs prove to me what I always suspected. I have always known that Canon and Nikon seemed superior in AF and my Pentax cameras.

Last night I discovered that it is quite possible that my eight year old MZ-S has better AF than my K20D, at least in a twilight setting. Where my K20D would hunt and give up, my MZ-S had no trouble finding a focus lock (using same lens). Now why is that?
Unless I am totally mis reading the charts, (which is possible), in bright to neutral light the difference is indeed only decimal points of a second, it is only dim light conditions where it blows out to over a second. Granted if the majority of your shooting was in these 'dim' conditions then this would be a major factor.
Merry Christmas.

PS: if I am mis reading the charts, please correct me.
12-18-2008, 03:03 PM   #23
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QuoteOriginally posted by UnknownVT Quote
I don't know - be very grateful for references/links to that assertion.
Here is a link to the thread about Popphoto admitting that they just reused the K10D test - as far as I am aware they have not tested the K20D.

https://www.pentaxforums.com/forums/pentax-news-rumors/21374-popphoto-admit-u...0d-review.html

12-18-2008, 03:54 PM   #24
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QuoteOriginally posted by cabstar Quote
I think the main reason why the Pentax seems slow is due to the AF confirmation.
Agreed.

You are focused actually before you get confirmation. You can actually push the shutter release button before your confirmation, since there is a very slight confirmation delay between the body focusing and the viewfinder displaying it. Trust me. Sometimes, it just seems slower because you're waiting for confirmation. But you are actually focused before the confirmation occurs. There just a little delay before you see it in the viewfinder. Try it yourself.
12-18-2008, 03:58 PM   #25
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One other oddity that someone mentioned on photo.net is that the K20D gets a little over 4FPS when using the battery grip in parallel battery mode. The K10D stays at 3FPS. They also noticed a slight AF speed improvement w/ the BG.

Note that this does *not* affect the reliability of predictive AF.
12-18-2008, 04:15 PM   #26
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QuoteOriginally posted by pentaxmz Quote
Last night I discovered that it is quite possible that my eight year old MZ-S has better AF than my K20D, at least in a twilight setting. Where my K20D would hunt and give up, my MZ-S had no trouble finding a focus lock (using same lens). Now why is that?
operator error?
12-18-2008, 09:34 PM   #27
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QuoteOriginally posted by kunik Quote
Iincidentally... of the three Pentax lenses I have right now (300F2.8, 16-50, 50-135) the 50-135 appears to have the weakest AF performance. I find this curious for a number of reasons. Anyone else experience this?
I've read others that say the 50-135 is slow focusing, but I've found just the opposite. I've gotten shots with my 50-135 and K20D that really surprised me. Here are a couple of examples:

135mm, f/2.8, 1/180s, ISO 2000 with flash


If you zoom into the full sized shot of the runners, you can actually read the small print on their running bibs!
103mm, f/2.8, 1/1250s, ISO 100


The rodeo was really tough as it was so dim, I was shooting at ISO2000 to ISO2500 all night. Still I managed to get some good shots.

The footrace was where I first saw how well the K20D and 50-135 worked for me. Out of over 50 shots, I had maybe 2 that were OOF, mainly due to the focus picking the wrong subject (I was letting the camera select the AF point).
12-18-2008, 09:37 PM   #28
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QuoteOriginally posted by UnknownVT Quote
I don't know - be very grateful for references/links to that assertion.
(snip)
Comparing - although they do look similar - there are enough differences at points that it would seem that PopPhoto did NOT just re-use the K10D AF test results.
They actually admitted to reusing the K10D data as "it was the same system". They were roundly condemned for doing this as it undermines the point of testing systems.
12-19-2008, 06:15 AM   #29
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I struggle to get my K10D to keep up with my 4-year-old granddaughter. What galls me is that I used to be able to catch my daughter, when she was that age, with a camera (MX) that was both manually metered and manually focused - I didn't get 'em all but I was able to catch plenty.

Doubtless, one reason for the difference is that I'm 62 - not 34. Also, I've probably gotten overdependent upon AF and have lost the instincts I used to have. I suspect the camera's limitations (e.g., poor predictive capability) and focus speed may also play a role, but it's clear that folks - like Russ - who know what they're doing can capture moving subjects quite well with a Pentax camera.

Maybe I need to just practice more.

Jer
12-19-2008, 10:33 AM   #30
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QuoteOriginally posted by Sailor Quote
I struggle to get my K10D to keep up with my 4-year-old granddaughter. What galls me is that I used to be able to catch my daughter, when she was that age, with a camera (MX) that was both manually metered and manually focused - I didn't get 'em all but I was able to catch plenty.
Doubtless, one reason for the difference is that I'm 62 - not 34.
With age comes experience - that often counts more than fast reactions.

Think back to your manual focus days -

I am guessing that if you were getting plenty of successful shots of faster moving action -
it's because you Pre-Focussed your lens and waited for the right shot -
so that the only delay was the shutter lag.
I'll bet you did not wait to focus the lens only when you saw the shot.

Auto-Focus is WAY faster than we can focus manually.

So the secret to your success remains the same -

Pre-Focus (half-depression on the shutter button) and trip the shutter when you see the shot -
then the delay is only the shutter lag (as the lens is already focussed) which is <0.1sec -
faster than any AF or even human reaction time.
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