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07-08-2016, 06:00 PM   #1
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Pentax K-1 Continuous AutoFocus Performance

DPReview just posted a very negative review of the K-1 continuous autofocus. I have owned a (full frame) K-1 for 2 weeks and have owned various Pentax DSLRs over the years (also currently own K-3). I have always used single (not continuous) autofocus and generally get good focus results. In order to protest the DPR review, I just tested continuous autofocus on my K-1 as follows: Pentax 300mm f4 DA* lens with aperture set at F/4 (for shallow depth of field). K-1 in autofocus continuous mode, sel 9 (red grid), continuously shooting shutter at medium speed. The focus hold setting was set to low. First frame action was set to focus priority. Action in AF.C Cont. set to focus priority. The ISO was set at 800 and the shutter speed (aperture priority exposure) was about 1/2000 sec. Like the DPR test, I had a person ride a bike towards me at relatively low speed. I focused the grid on the rider's head, depressed the shutter button and held it down for about 20 frames as the rider moved towards me and I maintained the focus grid pointed at the rider's head. I repeated this test several times. I was shocked and disappointed to find that the rider's head was in focus in only 30% of the frames. Therefore, apparently the negative DPR autofocus test results are valid. Of course, using an aperture like F/8 would substantially increase the percentage of in-focus frames. However, that would just mask the basic functional problem.

I am concerned about the performance of this important camera function and fear that it will limit the K-1 market share. I'd like to ask the following questions:

1) Does anyone have success with continuous autofocus on the K-1 or K-3? Is there some trick to making it work reliably (other than slow apertures)?

2) Does anyone know why technically the Pentax continuous autofocus performance is so poor and inferior to, say, Nikon D750? Is it due to less powerful (and less expensive) computational hardware in the K-1 compared to the D750? Is it due to inferior tracking algorithms? Is it due to the lack of some other proprietary hardware?

3) Is there anything that can be done to make the Pentax K-1 continuous autofocus more accurate and competitive?

These questions may seem simplistic but the problem is simple - the continuous autofocus does not work properly and reliably. Can we K-1 owners expect Pentax to fix this function in the K-1 or must we just except it as is? If the later, then Pentax should at least explain why and not advertise the capability (for example, claiming next generation autofocus hardware).

Other than this continuous autofocus issue, I think Pentax has created a wonderful and outstanding camera.

07-08-2016, 06:05 PM   #2
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Welcome to the forum ....
I think there has been some lengthy discussion regarding this subject.
Suggestion: search the forum.
Cheers!

This, to start you out:
https://www.pentaxforums.com/forums/190-pentax-k-1/325371-been-banned-dpreview.html
07-08-2016, 06:10 PM   #3
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Do you have a K-1? (you speak of we k-1 owners). Then you can just experience if it meets your needs and if it doesn't ask a specific question. You don't? We can't help you. Anyway you don't need dprreview.
07-08-2016, 06:12 PM   #4
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QuoteOriginally posted by Quark Quote
I was shocked and disappointed to find that the rider's head was in focus in only 30% of the frames
This would imply that the K-1 has worse AF performance than the K-3, which almost certainly isn't the case.

Did you have the "hold AF" setting set to off? If not, this would add a delay before the camera attempts to re-acquire focus, and it could explain the outcome.

QuoteOriginally posted by Quark Quote
3) Is there anything that can be done to make the Pentax K-1 continuous autofocus more accurate and competitive?
I think with practice and the right technique, you'll be able to greatly increase your keeper rate. Replacing the lens might eventually become necessary if your standards are high, but it shouldn't be needed for a slow-paced subject like the one in your test.

Remember than SEL-9 assumes that you keep a single AF point within the grid pointed at what you want to be sharp. If this isn't the case, repeat the test with auto-9 instead. In that mode the camera will maintain focus on what's closest within the 9-point matrix, rather the prioritizing a single point.

QuoteOriginally posted by Quark Quote
2) Does anyone know why technically the Pentax continuous autofocus performance is so poor and inferior to, say, Nikon D750? Is it due to less powerful (and less expensive) computational hardware in the K-1 compared to the D750? Is it due to inferior tracking algorithms? Is it due to the lack of some other proprietary hardware?
Pentax AF motors are slower (and the one in the DA* 300mm is noticeably slower than the best Pentax offers, which are the DC motors), and yes, I don't think the hardware in SAFOX is quite as advanced as what Nikon or Canon uses. Still, it's not supposed to be this bad.


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07-08-2016, 06:16 PM   #5
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Nice first post. Will you kindly post your images with EXIF attached either in an album here or linked to an external website? It will be helpful to those of us who have owned and used K-1 since early May if we could observe your results for comment and recommendation.
07-08-2016, 06:28 PM   #6
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I think the new DFA lenses particularly the 150-450 and the 70-200 are supposed to be much more accurate and faster at focusing. The new 55-300 lens may also offer some additional ability. The DA 300 has a relatively slow AF motor and I think you mentioned AF hold was on which Adam suggests turning off since the bias for holding focus should be zero in this test.


Disclaimer - I have a K-3 and no plans at present to have a K-1. But I am interested and curious about the results. As someone else suggested posting the full set with EXIF intact to Flickr or another photo hosting site and providing the link will help everyone understand this result better. Many here get better results using the K-3 and the K-1 is supposedly improved over that. Given your relative newness to AF.C there may be some user related factors as well. I personally have very little experience using AF.C so I am not the expert.

One last point - the camera positioning in the market is not such that it must compete evenly with the D750 in all types of shooting. The majority of the shots that most of us do are the type that AF.S will get - the performance there is stunning from what I see. It still may not reach the level of speed and silence that some may want but the level of performance per $ is crazy good. The sports and action shooters who do this professionally are likely to stay away from the K-1 - the guy who wants a few soccer pics of the kids probably will be OK with slower f/stops for DOF or a bit lower keeper rate. The point I'm making is that the camera's market isn't stong AF.C performance oriented so if it falls short but gives many advantages for the $ then it will still have a good run.
07-08-2016, 06:37 PM   #7
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QuoteOriginally posted by Quark Quote
I have owned a (full frame) K-1 for 2 weeks
and "... I just tested continuous autofocus on my K-1"


Implying that the OP does own a K1.
07-08-2016, 06:40 PM   #8
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The funny thing about human nature is that we often dwell on the negatives.

Pentax AF for moving subjects has never been market leading, no secret about that, but it has improved through the models. I don't think this criticism is a shock to us pentaxians. The shock felt is most likely by non-pentaxians as they learn of the superior K1 capabilities at a lower price point.

Again I remind myself of human nature here as I dwell on my adoration for the K1.

07-08-2016, 06:47 PM   #9
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30% keeper rate? I'm lucky to get one or two with the K3. Sounds like a vast improvement.
07-08-2016, 06:48 PM   #10
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Tony Northrup, in his review noticed that while the camera produced stunning dynamic range, the AF.C on the K-1 was sub par and it resulted in a disappointing keeper rate as compared to the competition.



QuoteOriginally posted by Quark Quote
DPReview just posted a very negative review of the K-1 continuous autofocus. I have owned a (full frame) K-1 for 2 weeks and have owned various Pentax DSLRs over the years (also currently own K-3). I have always used single (not continuous) autofocus and generally get good focus results. In order to protest the DPR review, I just tested continuous autofocus on my K-1 as follows: Pentax 300mm f4 DA* lens with aperture set at F/4 (for shallow depth of field). K-1 in autofocus continuous mode, sel 9 (red grid), continuously shooting shutter at medium speed. The focus hold setting was set to low. First frame action was set to focus priority. Action in AF.C Cont. set to focus priority. The ISO was set at 800 and the shutter speed (aperture priority exposure) was about 1/2000 sec. Like the DPR test, I had a person ride a bike towards me at relatively low speed. I focused the grid on the rider's head, depressed the shutter button and held it down for about 20 frames as the rider moved towards me and I maintained the focus grid pointed at the rider's head. I repeated this test several times. I was shocked and disappointed to find that the rider's head was in focus in only 30% of the frames. Therefore, apparently the negative DPR autofocus test results are valid. Of course, using an aperture like F/8 would substantially increase the percentage of in-focus frames. However, that would just mask the basic functional problem.

I am very concerned about the poor performance of this important camera function and fear that it will limit the K-1 market share. I'd like to ask the following questions:

1) Does anyone have success with continuous autofocus on the K-1 or K-3? Is there some trick to making it work reliably (other than slow apertures)?

2) Does anyone know why technically the Pentax continuous autofocus performance is so poor and inferior to, say, Nikon D750? Is it due to less powerful (and less expensive) computational hardware in the K-1 compared to the D750? Is it due to inferior tracking algorithms? Is it due to the lack of some other proprietary hardware?

3) Is there anything that can be done to make the Pentax K-1 continuous autofocus more accurate and competitive?

These questions may seem simplistic but the problem is simple - the continuous autofocus does not work properly and reliably. Can we K-1 owners expect Pentax to fix this function in the K-1 or must we just except it as is? If the later, then Pentax should at least explain why and not advertise the capability (for example, claiming next generation autofocus hardware).

Other than this continuous autofocus issue, I think Pentax has created a wonderful and outstanding camera.
07-08-2016, 06:50 PM   #11
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QuoteOriginally posted by jpzk Quote
and "... I just tested continuous autofocus on my K-1"


Implying that the OP does own a K1.
Yup, I'm not sure about all the negativity.

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07-08-2016, 07:00 PM   #12
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I use center point AF (spot) with AF continuous when shooting with the K-3II, and I do not have a problem with effective focus for bird in flight subjects. These settings require the shooter to perform effectively enough to track the subject in order to obtain proper detail in the image the camera produces. I do not have a K-1, but I would doubt very much that the AF would be degressed (less efficient) than the K-3II model. Using other than Spot (center point) AF for moving objects is something I do not prefer. To have effective testing, it would almost be a necessity, accompanied by a shooter that knows how to make use of the camera body with positive performance. It seems almost ridiculous that a review would label an advancement of a K-3II (the K-1) with a poor rating in anything.
07-08-2016, 07:16 PM   #13
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QuoteOriginally posted by Adam Quote
This would imply that the K-1 has worse AF performance than the K-3, which almost certainly isn't the case.

Did you have the "hold AF" setting set to off? If not, this would add a delay before the camera attempts to re-acquire focus, and it could explain the outcome.



I think with practice and the right technique, you'll be able to greatly increase your keeper rate. Replacing the lens might eventually become necessary if your standards are high, but it shouldn't be needed for a slow-paced subject like the one in your test.

Remember than SEL-9 assumes that you keep a single AF point within the grid pointed at what you want to be sharp. If this isn't the case, repeat the test with auto-9 instead. In that mode the camera will maintain focus on what's closest within the 9-point matrix, rather the prioritizing a single point.



Pentax AF motors are slower (and the one in the DA* 300mm is noticeably slower than the best Pentax offers, which are the DC motors), and yes, I don't think the hardware in SAFOX is quite as advanced as what Nikon or Canon uses. Still, it's not supposed to be this bad.
Adam,

Many thanks for your helpful suggestions. I will try "hold AF off" and "auto-9" and will try same setup using my K-3. I do not think the DA* 300/4 is the problem because it does single-focus almost instantly, much faster than needed to keep up with the rider.

Some of the commenters (to my original post) seem to think I am being negative about the K-1. Quite to the contrary. I just want it to be all that it can be. As mentioned, I did the test with the aim of rebutting the criticism in DPR which, of course, is a commercially influential site. If the K-1 cannot be among the best cameras at "continuous autofocus", being a retired techie, I'd just like to know basically why. Hopefully with technique refinement I can get my "keeper" rate of continuous autofocus shots up to an acceptable level. Obviously there are many photographic situations where continuous autofocus of moving subjects would be useful.
07-08-2016, 07:40 PM   #14
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Hi Quark,

Two other tips that could improve your keeper rate in addition to the settings suggested by Adam:

1. Always wait for the AF system to get an initial focus lock before starting your burst. Turning on the beep for focus lock might be useful. The difference this makes in percentage of keepers in AF C is significant.

2. To increase the speed of gaining an initial focus lock, start with the lens focused farther than the subject distance rather than closer. Pentax bodies seem to acquire focus lock easier moving in rather than going away.

These may not totally negate the disadvantages of Pentax AF C compared to better performing AF systems, but they should at least give it a fighting chance.

Scott
07-08-2016, 07:50 PM   #15
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DPReview reviewed the K-1?

I figured I would wait on buying a K-1 until after they had reviewed it.
By then, it would have been on the market for over a year and price would have come down.
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