Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-21-2017, 02:25 PM   #106
Junior Member




Join Date: Sep 2017
Posts: 31
QuoteOriginally posted by Winder Quote
What I'm saying is that the people who are getting good results are using F/4 - F/8. They shoot where the DoF is as large as the subject. As I have said previously, There is latency in the system which is exactly what you are seeing. The AF locks, but by the time the shutter releases the target point as moved out of the plane of focus when using F/2.8. As you say, using F/4 - F/8 doesn't actually test the AF speed. As you point out Biz-Engineer is shooting his horses are F/4 - F/8 so that most if not all of the horse fits in the DoF. Its not really much of a test for the AF as you could employ zone focusing and get the same result on a manual focus camera.
Exactly! At this point I surmise that you are spot on! I am leaning more and more towards the idea that people who are finding the autofocus tracking as super fast and accurate in the Z-axis, are most likely masking the significant delay (unbeknownst to them) with a large enough DOF. The shots like the cyclist by clackers, could be a luck shot, OR he might have some really good setup or technique. Since it is a one off, at this stage, I cannot pin point to how that shot came to be. I am not so confident that my shooting style is the problem, because after measuring my center spot area, I found that the most contrast areas were on the front of the dog within the area, and that if the focus was picking up the background, then the grass would be in focus much further behind the dog than what it is.

From my calculations at f/2.8 my DOF at 20 meters was 1.6 meters. Which is more than the dog, yet the focus wasn't encapsulating the whole dog, just the rear and the grass behind him. At f/4 it would be 2.2 meters, which might have been enough to bring the head into focus. At f/5.6 the DOF is 3.2 meters, and f/8 it is 4.6 meters.

What I have uncovered is that some settings do play a role in the length of that delay. And I think this delay is the key to the problem that people are experiencing. I think the autofocus method and mechanism of the camera is most likely great (with focus priority), since the results are consistently off. I hope I can identify the settings that can decrease this delay. So far the biggest one is JPEG.

Thank you Winder! Your earlier reply (a few days ago), made me at least realize I wasn't going crazy. And I have to thank clackers because he inspired me to go do more tests.
I probably would never dip far below f/4 on the 70-200 lens at 200mm. You loose a lot of sharpness below f/4 in the corners. But there are those rare shots where you want focus on a small area with sharpness right in the center.

For those that are not aware of what the issue is (since we are several posts in since this was brought up):
Here are pictures with low f-stop values from other camera manufacturers (These are 2008 and 2009 cameras).
Owl in flight
Arabian Horse
Running for a meal | Mabry Campbell Photography mabrycampbel? | Mabry Campbell |

The last one is a horse running towards the camera for a snack. You can see how the head is completely in focus and by the neck the focus has dropped off. In an attempt to duplicate a similar result, with over 900 shots, I got two shots with these kind of result.

Other Testers have found similar issues:
Pentax K-1 Review: The Best Landscape Camera Ever? - YouTube - You will hear their mention of the tracking (although it seems they are buffer hounds).
Special K? Pentax K-1 Review: Digital Photography Review
Winder also pointed this out.

Here is an example of me attempting to get the same kinds of shots:
https://www.flickr.com/gp/153388317@N08/7m3701

You will notice that some of the shots are at f/6.3 and yet I don't have focus on the target. It was the first couple of shots that highlighted the problem to me. I started tweaking settings and got some improvements.

I am planning on testing catch in focus, to see what results it yields.

09-21-2017, 04:26 PM - 2 Likes   #107
Junior Member




Join Date: Sep 2017
Posts: 31
Eureka!

With some new settings I now get 33% accuracy with Phase Detection AF set to Auto for 1st Frame Action and Auto for Action in AF.C Cont. This was out of a 109 shots.

With the new settings I get 41.8% accuracy with everything set to Focus Priority. This was out of 43 shots (the dog was done playing).

Here are the 41.8% accuracy settings:
Menu 1
--Phase Detection AF
----AF Mode: AF.C
----AF Active Area: SEL
----AF.S Setting: Focus Priority
----1st Frame Action in AF.C: Focus-priority
----Action in AF.C Cont.: Focus-priority
----Hold AF Status: Off
Menu 2
--Crop: FF
--Image Capture Settings
----File Format: RAW
----JPEG Recorded Pixels: XS
----JPEG Quality: 1-star
----RAW File Format: PEF
----Color Space: sRGB
--Dynamic Range Settings: All Off
--Noise Recution: All Off


With these settings I got this shot:


The nose is out of focus, the eyes are in focus and then by the time you get to the ears they are out of focus again. Very shallow depth of field. I got a total of 3 of these with very shallow DOF, placed exactly centered.

With the higher hit accuracy I can now notice that the Pentax 70-200 lens is also lagging at further distances and is more dead on at about 15 to 4 meters.

Thank you for everyone who provided some input. Sure Nikon and Cannon might have better Autofocus systems on the flagships, but I can live with 41%.
Who knows, there might be more to squeeze out in the future.
09-21-2017, 04:39 PM   #108
Veteran Member




Join Date: Aug 2010
Location: Adelaide
Posts: 470
I've been following this thread with interest, thanks for putting in all this work!


Just to be sure, the AF Active Area menu setting is SEL, not SEL S, SEL M or SEL L. Also have you tried SEL vs centre-point fixed?
09-21-2017, 05:08 PM   #109
Junior Member




Join Date: Sep 2017
Posts: 31
QuoteOriginally posted by krazykat Quote
I've been following this thread with interest, thanks for putting in all this work!


Just to be sure, the AF Active Area menu setting is SEL, not SEL S, SEL M or SEL L. Also have you tried SEL vs centre-point fixed?
Yes it is just SEL. And I have compared SEL vs Center point and they are the same. The only difference is that with SEL you can move which sensor you would like to use. I haven't tried different sensors other than the center one at this point. But from what I know, the best sensor is the center one.

When I have time I will experiment a bit more. I might want to map out all my sensor locations at one stage. So far I have just done the center one.

09-22-2017, 10:41 AM   #110
Site Supporter
Site Supporter




Join Date: Mar 2008
Location: Prince George, BC
Photos: Gallery | Albums
Posts: 2,806
For giggles, you may want to do a run using Green mode. Then all control is surrendered to the K-1's Scene Analyze mode and all outpuut is jpeg. This would be the true test of larency, I believe.
09-26-2017, 02:36 PM - 1 Like   #111
Junior Member




Join Date: Sep 2017
Posts: 31
QuoteOriginally posted by jbinpg Quote
For giggles, you may want to do a run using Green mode. Then all control is surrendered to the K-1's Scene Analyze mode and all outpuut is jpeg. This would be the true test of larency, I believe.
It would be just for giggles. Auto mode is a modified P mode with all the other settings as Auto. Which gives you no control over Aperture, which could hide a lot of the focus problems in the DOF. More on that in a bit. You also have no way to tell the system what to focus on. It automatically picks it's subject.

After doing some more tests I can report that AdobeRGB mode, with PEF, seems to be about the same as sRGB. BUT I didn't get a lot of shots in to make this definitive. With my new test there might even be a possibility that AdobeRGB is a bit better for autofocus than sRGB, but my sRGB shots were a bit worse than my last measurement. That said I had a lot less shots this time (~50 small sample size), where as before I had 110. So I can at least report that AdobeRGB is the same for Autofocus speed delay or better than sRGB.

The one extra measurement I took this time, was measuring the accuracy, if my DOF was half that of the subject's length. The method was to see how close the focus was to the center spot target. If that was less than 1/4 of the subject length, then I counted it. This caused the percentage of in-focus pictures to almost double in count. In one test the percentage went from 18% to 35%, and in another it went from 33% to 50%. I will discus below how this makes it difficult to compare accuracy tests.

So here is another set of system settings that appear to work well:
Menu 1
--Phase Detection AF
----AF Mode: AF.C
----AF Active Area: SEL
----AF.S Setting: Focus Priority
----1st Frame Action in AF.C: Focus-priority
----Action in AF.C Cont.: Focus-priority
----Hold AF Status: Off
Menu 2
--Crop: FF
--Image Capture Settings
----File Format: RAW
----JPEG Recorded Pixels: XS
----JPEG Quality: 1-star
----RAW File Format: PEF
----Color Space: AdobeRGB
--Dynamic Range Settings: All Off
--Noise Recution: All Off

I want to address some of the topics I have become aware of as I have worked on solving the autofocus problem:

The DOF plays a big role in how we asses whether something is in focus. I recently watched this review of the Nikon D850 vs the Nikon D5 focus tracking:

Identical setups were used for both the D850 and the D5 and in Matt Granger's tests he found the D5 to be about 90% accurate and the D850 to be about ~65% accurate. Both the D5 and the D850 have the same autofocus system. In my opinion the main difference, is the pixel pitch. The D5 has a pixel pitch of 6.41 Ám. And the D850 has a 4.35 Ám pixel pitch. That is a very significant difference, and is the main component in assessing the circle of confusion for a camera. The larger the circle of confusion the greater the DOF will be, with everything else being the same. It very well may be that the D5 is an autofocus beast because of it's larger circle of confusion due to larger pixel pitch.

Click here for more on Circle of Confusion

I am highlighting this because I feel it is important to understand how difficult it is to asses the autofocus problems. Especially trying to compare two systems to each other. The Pentax K-1 has a 4.86 Ám pixel pitch and the Pentax K-3 II has a 3.88 Ám pixel pitch.
A larger circle of confusion is also going to give you a larger DOF, with everything else being the same. If you are hunting for a very shallow DOF then this becomes a consideration. It will also show more focus flaws as your DOF becomes smaller.

I am therefore fully aware that for some people the accuracy will be a lot different depending on your DOF, relative to the speed of your subject towards you.

Some additional notes:

I found the Pentax 70-200 to be back focusing more often from 15 meters and further and then suddenly jump much closer into focus at 10 meters. So pay attention to your focus ring throw, it seems to play a role in how close the focus lands and could be a big culprit in your results on your K-1.

The contrast lines on your subject do play a role. clackers pointed this out before, but in the picture below you can see how the camera chose a different spot than what would be obvious.
The line between the top of the lip and the fur was used and specifically the line at the corner of the mouth.


If you want to measure your center point area, you can follow these steps. The link is to the spot where the method is described:
Solving AF Problems - 8 Common Autofocus Problems - And Their Solutions - YouTube

In my setup I used a softbox with the lights on and a square electrical tape in the center. I took a picture everytime the focus settled. I then stacked the pictures and drew red lines to include a piece of the electrical tape from the side I approached it. Then each layer was set to 25% opacity and I got the following result:

The blue box is an action I created to draw it onto the image. I can run the action at anytime to see where the center spot was. You can duplicate this for all your focus spot. You will notice that a lot of the spots are not where they indicate in the view finder.

It will also be useful to make sure your lenses are fined tuned to your camera. I used the Dot-Tune method and this video gives you instructions. On the Pentax camera you will be looking for the Diamond in the bottom left of the view finder. When lit it will indicate detected focus.
For most of my lenses I found this to be great. But for one lens it ended up front focusing, and I had to repeat the process. So take sample pictures with different setups to make sure the focus is where you expect it to be.

I hope this is useful for anyone trying to diagnose their own issues.
09-28-2017, 10:42 AM   #112
Pentaxian
angerdan's Avatar

Join Date: Feb 2015
Photos: Albums
Posts: 1,004
Found these two article, some parts are identical to your experiences. Most important is to disable develop options, since a developed JPG is included in every RAW.
Guide to Camera and Autofocus Settings for Shooting Sports - Articles and Tips | PentaxForums.com
DSLR Guide for Shooting Sports II: Horse Racing - Articles and Tips | PentaxForums.com
09-30-2017, 01:40 AM   #113
Pentaxian




Join Date: Apr 2013
Location: Brisbane, Australia
Photos: Albums
Posts: 714
Original Poster
QuoteOriginally posted by Winder Quote
Did you ever get the AF issue resolved? I have been pretty outspoken about the below average AF performance of the K-1, but it is significantly better than the AF in the 645z that you have. Outside of tracking moving subjects in mixed and low-light it performs very well. For travel and landscape photography its probably the best DSLR you can buy.
I actually returned the camera after getting back from the holiday, my dealer was gracious enough to give me a store credit as I know them very well. I tested it with another 15-30 and did not find it to be really any different. I love the K1, its an excellent camera and an extension of the wonderful 645z.

As my second kit I now have a 5DmkIV and a selection of Canon lenses and I love it. The overall image quality from the camera is very comparable to the K1 for the applications that I now use it for, which is travel, handheld live view with tracking, long lens work and some landscape, along with quite a bit of astro. I was recently in Cambodia and one night I was in a Tuk Tuk and some locals came alongisde on their motorbike, I held the 5D out the side in live view with a 35mm f/2 IS lens attached and it tracked perfectly. I got some great shots and the K1 would have possibly struggled a lot with that. The AF system (both through the viewfinder and in live view) on the 5DmkIV is another level above the K1. I also much prefer a through-the-lens IS system that you can see working, its much better for framing etc and nets the same result in internal camera IS.

I am still using my 645z for landscape exclusively.

If I did not have the 645 system, I may have a different kit which would possibly include the K1.

You buy a system for what you need it for, so when its great for somebody else if may not be the case for you, but thats fine too.

Scott

10-02-2017, 09:30 AM - 3 Likes   #114
Junior Member




Join Date: Sep 2017
Posts: 31
I am writing this post as a summery. I have developed quite a tentious rapport with the K-1 Autofocus system. And I will be leaving this topic for others to contribute to.

So after I had practiced with over 2000 shots to get a good setup, I went hiking with the Pentax K-1. I have to say that the Autofocus, with a moving subject, is just not what you would expect. Within the forest, I got about 10% success. With the lower light in the forests I really needed that lower F-stop value to get the shutter speed a bit higher. I think 2351HD has a good point: The K-1 is great for landscape, probably the best in that category. It will most likely be a tie for portrait shots as well.

I now have read all the Guides (that I could find), including the ones suggested by angerdan. As well as come across posts by biz-engineer (1, 2, 3), who got those amazing mallard shots, and everyone who is honest about the autofocus of the Pentax K-1 (such as Winder), and the conclusion is as follows: Yes you can get great shots of moving subjects, but be prepared to push your DOF larger than you expect. Most common suggestion I found so far is that you need the right setup. It is true that the more you prepare for where the subject is going to be the better your focus success will be. And that there are settings that affect the lag between autofocus and shutter release. But even after all of these considerations, you might be better of with a different camera if you are interested in more action shots. I have totally fallen in love with the K-1 but I think 2351HD has a good point and once I get more into action, I will most likely invest into a Nikon D500 as a second camera (since I have some Nikon glass, and the D500 is comparable to the K-1 in price).

My only critique so far is that there is a lot of woo-woo, and no one really knows what a good setup is. I think I know why. The K-1's autofocus tracking (z-axis) reminds me of Jack White's comment of what kind of guitar he likes to play. He likes fighting a guitar to get the sound he wants out of it. He doesn't like playing easy guitars, because he wants there to be a struggle. For him the struggle encapsulates the artistry, which might be very true for some K-1 users. I think this process gets people to settle on settings and styles that allow them to get the best out of the K-1 (for them), but in the process they have given up on possible shots as well as adopted some woo-woo into their process. It also makes it difficult for them to relay to others what to do, and this is the point of my critique! After scouring many posts for autofocus information I came across a lot of "they don't know how to use the camera" (refering to reviewers), and "do what I do", or "do what he does" (with vague references) and "if you are struggling then it is your fault".

The one nugget I found that gave me some useful information was the post by beholder3 (I found this by following a link by clackers to a post by biz-engineer who referenced this post; This was before angerdan link) on "Guide to Camera and Autofocus Settings for Shooting Sports". The nugget was found in the "Drive Mode and File Format, Image Style" related to turning down the JPG values. While you are checking out that section, note the horse jumping picture right below "Drive Mode and File Format, Image Style". You will find an image that appears to be back focused (if studied closely), but the large DOF hides it. The rider is right where the post is (beholder3 comments that he focuses on the rider's face), yet there is a lot more ground in focus behind the horses rear hooves than in front of the post.

This doesn't mean you cannot find that low F-Stop value shot that is exactly where you want it; I did it! But it takes the right settings, understanding exactly where your target is going to be, and a lot of practice (2000 shots of the same thing) and I got my percentage to 42%. In a real life woodland scenario it dropped down to 10%. And even in the 42% environment my results would drop down to 15% if the light conditions changed. (Back in the woods): I had my wife handle the camera for a while, with a moving subject, and the first thing she complained about (without knowing any of the back story) was that the focus wasn't where she wanted it.

In my opinion there are 3 main issues with the Pentax K-1 Autofocus system.
  1. The first is the introduced delay between autofocus acquisition and shutter release. This is a settings issue that can be resolved with settings listed here and here.
  2. The second issue is that the AF system is just not that great at z-axis tracking. It hunts quite a bit more than what people expect. With Shutter Release Priority you can see how much it hunts by looking at the first image sequences of this post. I think in Focus-Priority mode it sweeps back and forth and uses the catch in action mechanism to fire the shutter. The more you look at sequences (2500 on my end), this becomes quite obvious when you notice where the missed focus lands. It also makes it unpredictable to know what will be used to determine when the subject is in focus. If it sweeps from the back of the subject, then a contrast line towards the back of the focus point will be used and vise-versa.
  3. 3D tracking or equivalent mechanism is just not a viable option on the K-1. You can select the feature but it won't do what you hope it will.
I surmise that anyone that gets accuracy levels above 45% is using large DOF to hide the flaws (second part of this post covers that) or the subject isn't moving that fast in the z-axis plane compared to the DOF (this is a common work around, I saw, by shooting the subject from the side).
I don't think it would be helpful to try and obscure these faults. If we can identify them and stress how important they are to the full system, then it allows Pentax to focus on improving these faults in later releases of their products or firmware updates.
For now expect to struggle with the system, and if you really are hoping to get into action shots, you might want to pickup a second camera.

Who knows, a firmware update might resolve all these issues in the future. I keep my fingers crossed.
10-02-2017, 04:16 PM - 1 Like   #115
Loyal Site Supporter
Loyal Site Supporter
clackers's Avatar

Join Date: Jul 2013
Location: Melbourne
Photos: Albums
Posts: 12,884
QuoteOriginally posted by Jeffvan Quote
Most common suggestion I found so far is that you need the right setup. It is true that the more you prepare for where the subject is going to be the better your focus success will be. .
That's right, Jeff.

It doesn't matter what brand you shoot, if something is approaching head on you will have to allow for depth of field, which gets smaller as the subject distance decreases.

But you can still shoot at wide apertures if you want.

The girl I photographed was at f4, not f8 or f11 as you were estimating, and she ran right past me, one continuous press of the AF backbutton. Mind you, f8 is very common for sports and wildlife, since a Canikon hobbyist will be using a Sigma or Tamron 150-600 that begins at f5 or f5.6 at the wide end and can only get to f6.3 at the long.

The two casual handheld shots below I took at the weekend are wide open at f2.8. I was happy to sacrifice image sharpness (the Tammy like all lenses is better a stop down) because I thought the tradeoff with background separation was worth it. The light is poor ... overcast, no particular direction to make shadows, and ISO 320 and ISO 800.

By all means, get your settings right, pan with a sports photographer's technique to track, and of course, with either PDAF or CDAF, move yourself to make sure the subject is lit well and that there is a nice line to focus on, either on the subject itself or a proxy object.

As a hobbyist who loves to shoot any subject in any style, I have used Pentaxes to shoot cricket, baseball, air shows, trail running, AFL football, soccer, American football, kayaking, rodeo, dancing, et al. That's everything moving from 10kmh to 300kmh.

If Sports Illustrated want to reverse recent history and hire guys and give me a pair of D5s (they have a second CPU to help AF calculations), a 400mm f2.8 and 70-200mm, I'll do that. But until then, there's no action I wouldn't shoot.




Last edited by clackers; 10-02-2017 at 11:52 PM.
10-02-2017, 05:17 PM - 2 Likes   #116
On Hiatus. Back Later.
Loyal Site Supporter
monochrome's Avatar

Join Date: Mar 2008
Location: Flyover Country
Photos: Gallery | Albums
Posts: 24,427
I agree we too often expect K-1 to be a tool it was never intended to be and to satisfy a use case it was never marketed to fill.

I suspect if Pentax releases a major upgrade to the autofocus system in conjunction with a new camera body it will come when the K-3 is replaced. I would not be surprised to find it more hardware driven and less Firmware upgrades driven. Doing so would make the K-3n a use case choice, rather than a smaller K-1, with KP continuing as a enthusiast / generalist camera.

But I actually believe they’re working on something no one is talking about - and that’s holding back everything else.

It will come

Last edited by monochrome; 10-06-2017 at 07:09 AM.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
action, af, af.c, auto, autofocus, board, camera, device, dslr, focus, full frame, full-frame, k-1, k1, lens, mode, pentax k-1, people, results, shot, spot, time, view
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
To K1 or not K1 - that is the question? interested_observer Pentax K-1 78 07-15-2017 03:58 PM
K1, K-mount and Samyang autofocus lenses TheGamer Pentax SLR Lens Discussion 10 05-14-2016 03:21 AM
K1 autofocus with aps-c lenses in crop mode slip Pentax K-1 1 05-09-2016 04:51 PM
SAFOX 12 autofocus can indicate multiple points in focus! bwDraco Pentax K-1 16 04-29-2016 01:24 AM
K10d Autofocus Tracking Workingdog Pentax DSLR Discussion 28 12-11-2007 05:40 AM



All times are GMT -7. The time now is 09:52 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top