Originally posted by clackers Correct, so in the dog pictures above, the AF module never focuses on the dog.
It focuses on a particular line or edge under a particular AF circle on the dog. That can be the tail or the collar, whatever it sees under a point.
I like to remove the camera's guesswork and pick the AF point in advance, like the centre one for an action shot.
So I measured my Center Spot location and created an Action in PS to place it on the picture. I don't have new pictures, so I am using some of the pictures from before to give examples of where the center spot is.
You will see quite a few contrast lines, which should be enough for the phase detection, within the center spot. I flipped the images to Black and White to show the contrast lines.
Here is one of the first pictures I shared in this thread:
Here is a side by side of the brown dog. There is less contrast lines between his ears and tail than between his nose and eyes. There is a another strong contrast line between the Frisbee and his chest and nose.
But I agree:
it is a variable that should be removed from the equation. I will try to setup a more reliable test method to make sure there are no problems related to my shooting style.
Originally posted by Winder You don't need 1/5000 of a second. 1/1000 should be fast enough to freeze the motion of your dog. The DoF at F/2.8 is going to be your problem. Most of the people showing good results are shooting at F/4 or even F/8. They aren't stressing the AF as much as you are with F/2.8 at 200mm. When the DoF is larger than the subject it a lot easier for the camera to get the head in focus. Change your setting to F/5.6 and give it a try. You will get much better results. The K-1 AF isn't going to give you great results at F/2.8 200mm.
Winder thank you for that information. I mentioned above that I am shooting at f/2.8 on purpose. I agree that I can get excellent pictures at f/8. What I am attempting to do is find the
best settings for autofocus, for a target moving towards me. This will give me more choices, so that I may select lower F-stop values and trade that for better ISO values and shutter speed values. The 1/5000 choice was just based on the ISO range and brightness at f/2.8 that day. The f/2.8 is a deliberate choice, since it will highlight any flaws in the autofocus system. Furthermore, I would like the option to separate the face of the dog from the background and its body. I noticed a lot of suggestions to increase the DOF.
I am experiencing a lot of focus issues. There are other people that echo my findings. Then on the other hand there are people that experience no autofocus problems. Like clackers, and biz-engineer. In some of their pictures I find large DOFs (which is great if that is what they wanted, but if there are any autofocus flaws in those shots then I can't discern it).
To highlight the autofocus success and failures we need a shallow DOF, compared to the target, so we can find where the autofocus lands. We also need shot sequences to be able to see if there are misses by the autofocus. biz-engineer seems to cover a lot of those bases, but we cannot see where the focus really lands since the whole target is in focus.
So why are some people finding the autofocus lacking and other don't?
I am attempting to isolate the variables, which is difficult because I have only one pentax camera and one 70-200 lens. I am attempting a more scientific approach to the solution, which requires identifying the variables. biz-engineer and clackers might have a better version of the K-1 than what I have, or better lenses than what I have. Those are very possible variables. They might also have a better shooting style or better settings.
To figure this out, I am trying different settings to identify and eliminate variables. I am trying to avoid the woohoo effect where we feel like X and Y is the solution, and instead be more empirical with the results. It is frustrating and tedious on my part, since I am noticing a lot of woohoo, and testing other's settings with no observable change (I do need a better setup to retrieve more empirical results).
A common woohoo I have heard is: Person X didn't know what they were doing and that is why they had bad results with autofocus. I find this doubtful when people who have a lot of camera experience (NOT ME, Other testers) suddenly consistently get bad autofocus results with a pentax. Questions I have are: what settings did they get wrong? what did they need to do differently in their style, that is different from other camera manufacturers? If the solution is a larger DOF, does that really mean the autofocus of the pentax is on par with other camera manufacturers? I want to know as many true things and as few false things as possible. I have no bone to pick here, just a drive for getting the most out of my K-1 and lenses.
I will be working on a better rig to eliminate my shooting style. If I find the best settings for the autofocus system, and I am still experience problems, then the only possibility is that my lens or camera, or both are not on par with what biz-enginner or clackers'. At that stage I might rent another K-1 and a lens and do the same tests and see what I get. Maybe biz-enginner and clackers have exceptional versions of the camera or lenses. Or they actually have similar focusing issues but have been able to overcome the problem with style and DOF tuning. If you go back to the sequence of shots with JPEG and Focus-Priority you will see that the focus is almost exactly on the face, for many of the shots. So yes, a larger DOF would hide this problem completely.
I hope this highlights how many variables are at play, and so far I have found that RAW(DNG) is a factor in the delay, at least in my camera, between autofocus and shutter release. This could be related to the embedded jpeg in the DNG file, or all RAW files have this issue. But I need to do more tests to determine this. But for now I need to take a break (while I travel) and it will take some time to build a rig to test autofocus and eliminate my shooting style as a factor. I am hoping with a rig that runs at a constant speed, I can actually measure the delays and location of the focus more accurately. This will allow for much more precise determination of which factors play an actual role in getting the best autofocus results.
I apologize if anyone is frustrated by my posts. I truly do value any input, which would lead me to get better results and identify more variables.
Thank you!