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10-26-2012, 08:30 PM   #1
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K-5 IIs Low-Light AF test video

This was performed in an area with at most 0EV (the Pentax spot meter doesn't go any lower). The K-5 couldn't focus at all on any part of the scene, while the K-5 IIs locked on every time. Note that we were focusing on the floor, not the bed.


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10-26-2012, 08:38 PM   #2
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The AF improvement should be really helpful for taking photos of birds and animals at dawn and dusk - which is the best time to find them in my part of the world! Thanks Adam!
10-26-2012, 08:41 PM   #3
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So was the AF really improved (accuracy, precision, AND speed/capacity to lock) or was the system optimized on time-to-lock at the expense of accuracy/precision? (Accuracy and precision in any system, photographic and otherwise, tend to suffer as sensitivity goes up.)


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10-26-2012, 08:43 PM   #4
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Aside from better low-light focusing, is the K-5 II(s) auto focus faster and more accurate? Or is it the same as the K-5? The auto focus is my real reason for wanting a K-5 II instead of a K-5.

10-26-2012, 08:44 PM   #5
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QuoteOriginally posted by stevebrot Quote
So was the AF really improved (accuracy, precision, AND speed/capacity to lock) or was the system optimized on time to lock at the expense of accuracy/precision?
Based on what I've found so far, the K-5 II AF is in fact able to operate in much darker conditions than that of both the Pentax K-5 or Canon 7D. The focusing speed doesn't seem to be any faster than that of the K-5 during the day, though. Controlled tests (to be done tomorrow) should confirm this. Accuracy is better overall both when it's dark, and in continuous mode during the day.

QuoteOriginally posted by RobG Quote
The AF improvement should be really helpful for taking photos of birds and animals at dawn and dusk - which is the best time to find them in my part of the world! Thanks Adam!
Indeed- if there's little light and your subject is out of range of the AF assist light (or might get scared away by it!), then yeah, it seems like the K-5 II might be the right tool for the job.

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10-26-2012, 09:00 PM   #6
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QuoteOriginally posted by Adam Quote
Based on what I've found so far, the K-5 II AF is in fact able to operate in much darker conditions than that of both the Pentax K-5 or Canon 7D. The focusing speed doesn't seem to be any faster than that of the K-5 during the day, though. Controlled tests (to be done tomorrow) should confirm this. Accuracy is better overall both when it's dark, and in continuous mode during the day.
Good to hear. AF is not that big a deal to me, but an improvement in this area is always a good thing.


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10-26-2012, 09:09 PM   #7
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QuoteOriginally posted by Adam Quote
Based on what I've found so far, the K-5 II AF is in fact able to operate in much darker conditions than that of both the Pentax K-5 or Canon 7D. The focusing speed doesn't seem to be any faster than that of the K-5 during the day, though. Controlled tests (to be done tomorrow) should confirm this. Accuracy is better overall both when it's dark, and in continuous mode during the day.
It sounds like the K5ii AF hunts a lot less than the K5, so that would be an improvement even if the actual speed of adjustment is the same.

QuoteQuote:
Indeed- if there's little light and your subject is out of range of the AF assist light (or might get scared away by it!), then yeah, it seems like the K-5 II might be the right tool for the job.
I'll be buying one - I just need to decide between the K5ii and K5iis.
10-26-2012, 09:33 PM   #8
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QuoteOriginally posted by RobG Quote
I'll be buying one - I just need to decide between the K5ii and K5iis.
Maybe you'll find this discussion about omitting AA-filters interesting.

10-26-2012, 11:08 PM   #9
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QuoteOriginally posted by Class A Quote
Maybe you'll find this discussion about omitting AA-filters interesting.
I should probably reply there, rather than post another response which is off-topic to this thread.
10-26-2012, 11:24 PM   #10
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Adam, what about accuracy with fast primes ? Is there any help from f2.8 center point ?
10-26-2012, 11:51 PM   #11
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Sounds great for slow lenses too, as my Sigma 150-500 + 1.5x TC.

Last edited by Ash; 10-27-2012 at 12:13 AM.
10-27-2012, 12:57 AM   #12
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QuoteOriginally posted by sargasa Quote
Adam, what about accuracy with fast primes ? Is there any help from f2.8 center point ?
I haven't really investigated this, but the low-light performance didn't seem to be better using the 85mm F1.4 compared to the 18-135mm. I have a hunch that the center point won't help much in low light, as you benefit a lot more from having all 11 points enabled then. Daytime tests are planned for tomorrow, but TBH, I have a hunch that we won't observe much of a difference compared to the K-5.

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10-27-2012, 02:04 AM   #13
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QuoteOriginally posted by Adam Quote
I haven't really investigated this, but the low-light performance didn't seem to be better using the 85mm F1.4 compared to the 18-135mm.
The f/2.8 AF sensor is not meant to be better in low-light. The "f/2.8" does not refer to light levels, but to the length of the baseline of the AF area. The longer the baseline, the more accurate AF can be.

QuoteOriginally posted by Adam Quote
I have a hunch that the center point won't help much in low light, as you benefit a lot more from having all 11 points enabled then.
You seem to link "AF accuracy" with the capability of a camera to achieve good focus in action situations. I believe most people link "AF accuracy" with the level of precision at which a camera can focus on a subject (typically stationary, as to not measure AF speed).

QuoteOriginally posted by Adam Quote
Daytime tests are planned for tomorrow, but TBH, I have a hunch that we won't observe much of a difference compared to the K-5.
Unless Pentax have screwed up the implementation, an f/2.8 AF area must be more precise than an f/5.6 area (the standard areas).

Actually demonstrating the superiority of the centre f/2.8 AF area in terms of AF accuracy is not easy since every AF attempt inevitably reflects on small tolerances and inaccuracies. However, in practice, on average a higher precision f/2.8 AF area will yield more shots in better focus than an f/5.6 area.

That's why high-end bodies all have f/2.8 cross sensors and Pentax went through the trouble of adding at least an f/2.8 line sensor to the K-5 II.
10-27-2012, 04:03 AM   #14
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QuoteOriginally posted by Adam Quote
This was performed in an area with at most 0EV (the Pentax spot meter doesn't go any lower). The K-5 couldn't focus at all on any part of the scene, while the K-5 IIs locked on every time. Note that we were focusing on the floor, not the bed.

Pentax K-5 vs K-5 II / IIs low light autofocus test - YouTube

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What is the practical side to shoot in such condition? No light, no photography.
10-27-2012, 05:43 AM   #15
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QuoteOriginally posted by ogl Quote
What is the practical side to shoot in such condition?
You need to get out more

Maybe shoot a low-light concert or something. Look at for example UnknownVT's 'K-x in Use' thread, where he shoots almost every evening in light at 0EV or below.

Or think about those poor wedding photographers who may be prohibited from using flash or even the AF assist light in a church setting. Or those birders with long slow telephotos chasing small birds in shady undergrowth. Etc

Good AF (and IQ) at low ambient light has a multitude of photographic uses. In fact it's about the most compelling reason for many people to go with full-frame.
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