The Ugly Truth About Pentax AF (Cuteness included)

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MightyMike Forum Pro • Posts: 38,691
The Ugly Truth About Pentax AF (Cuteness included)

We all know Pentax AF is not perfect, we all know its not up to par when compared with the other systems, that really doesn't need to be said over and over again. However just how bad or how good is it? Well the correct answer is YMMV, A skilled photographer will likely get more keepers than a none skilled photographer. The more patience, effort and concentration into achieving the best out come the more keepers you'll get. The more you avoid situations the camera will fowl up in the more keepers you'll get. The better the lens on the camera the more keepers you'll get. But lets face it, we're not all perfect nor do we all own the best gear. I've said it before as a joke with some truth in it, the more bad photos I get the longer I can stay out and shoot for and the less I have to edit when I get home. Sure I do want lots of good photos, but I also want to enjoy just being out and taking pictures too.

So the following is 12 examples of focus tracking on my dog at the dog park on a light overcast afternoon. Now there are some things you may want to know. I shot with the K-1II, TAv, 1/2000th sec (probably should have been faster), F8.0 once but F4.0 the rest of the time, in APS-C and FF modes. AF-C, AF Hold set to low, SEL25 (could have used Auto9). However another thing that may be important to know and you'll see it in the images is my dog is like a shaggy pile of fur with few features to lock onto and track, therefore if the camera got any part of that fur ball running it should be considered a win if not a perfect outcome. I figured when the dog was running full speed it was going about 25-30km/h (15.5-18.8mph) and of course at close range. I also zoomed while shooting therefore the dog will not appear to be getting larger in the frame as he approaches until such a point where I can't zoom out any further. I assure you he covered a lot of ground in a very short amount of time.

I'll use this as my rating system

1) Perfect, spot on focus on the face (or sideways on the body)
2) The camera got some part of the dog in focus (This could be subjective as to whether the camera+lens didn't keep up or whether it just chose a different part of the fur ball to track)
3) The camera failed but that could be because the dog got too close, or I couldn't follow the dog and the dog left the AF area (this could be subjective)
4) Total fail, the camera clearly lost focus for no good reason

Each sequence will be in 2 photo streams, the first will be the series of the full photos resized to 900x600 pixels each for APS-C or 1200x800 pixels each for FF and sharpened. The second stream will be of 800x800 pixel crops for APS-C and 1200x800 pixel crops for FF, no extra editing. The crop sequences don't always show whats in focus for obvious reasons. With each stream I'll include a series of numbers (1-4) as shown above rating each frame.

1st sequence APS-C mode 15 photos in 4-5 seconds, the camera locked onto another dog during the sequence and then back so it still got perfects even if it wasn't the intended dog
Pentax F 70-210mm F4-5.6 @ F8.0 (extra deep hood)
Ratings (4,4,2,4,1,2,2,2,4,2,1,1,1,1,1)
40% perfect ratio (however more so as the dogs stopped moving much on the Z-axis, 73.3% the camera did its job ratio (combined #1 and #2)
Full Frame [8.8mb]
Crops [6.3mb]

I switch now to my preferred lens the Sigma 100-300mm F4.0 EX DG @ F4.0 used this way for the rest of the sequences

2nd sequence APS-C mode 18 photos in 3-4 seconds full head on Z-axis run
Ratings (1,2,4,1,4,2,2,1,1,1,2,4,4,2,2,3,2,2)
Just 27.8% perfect, 72.2% the camera did its job (combined #1 and #2)
Full Frame [7.5mb]
Crops [5.4mb]

3rd sequence APS-C mode 20 photos in 4-5 seconds full head on Z-axis run
Ratings (4,2,4,2,1,1,1,1,1,4,1,2,4,4,4,4,4,3,3,3)
Just 30% perfect, and only 45% the camera did its job (combined #1 and #2) what appears to have happened here though was the camera just couldn't keep up, it was following but from behind the dog and in once instance it got ahead of itself.
Full Frame [8.4mb]
Crops [6.0mb]

4th sequence FF mode 20 photos in 7-8 seconds, starts as head on transitions to side run then to running away from me.
Ratings (2,2,2,1,2,4,1,4,1,2,1,2,1,4,4,1,1,1,2,1)
45% perfect, 80% the camera did its job (combined #1 and #2)
Full Frame [12.9mb]
Crops [9.1mb]

5th sequence FF mode just a short 8 photo burst in 2 seconds head on
Ratings (4,2,4,4,2,1,1,1)
37.5% perfect, 62.5% the camera did its job, rough start to this one but good finish
Full Frame [5.4mb]
Crops [3.6mb]

6th sequence APS-C mode 12 photos in 2-3 seconds head on
Ratings (4,2,1,1,1,1,4,2,3,3,3,3)
33.3% Perfect, 50% the camera did its job, 33.3% too close!
Full Frame [5.3mb]
Crops [3.8mb]

7th sequence APS-C mode 14 photos in 3-4 seconds head on, focus hold could have been set to higher. the first few photos didn't capture the dog due to interference from easier to focus on items behind the dog so I gave them a rating of 2 as the camera did its job it just didn't know what it was supposed to do.
Ratings (2,2,2,1,1,1,2,1,1,4,1,1,1,3)
57.1% Perfect, 85.7% the camera did its job
Full Frame [8.3mb]
Crops [5.0mb]

8th sequence APS-C mode 12 photos in 2-3 seconds towards me to sideways to away from me
Ratings (2,1,4,1,2,2,1,1,4,4,4,1)
41.7% Perfect, 66.7% the camera did its job
Full Frame [4.9mb]
Crops [3.6mb]

9th sequence APS-C mode 15 photos in 2-3 seconds, head on to sideways to too close. I gave a couple of #1 ratings when the camera maintained focus on the other dog towards the end.
Ratings (2,4,2,4,2,2,1,2,2,1,2,2,1,1,3)
just 26.7% perfect, however 80% the camera did its job
Full Frame [6.3mb]
Crops [4.6mb]

10th sequence APS-C mode 14 photos in 3-4 seconds slower trot speed relatively head on
Ratings (4,2,1,1,2,1,1,1,1,1,1,1,1,1)
78.6% Perfect, 92.9% the camera did its job, clearly the slower pace of a trot is something the camera can handle pretty well!
Full Frame [6.4mb]
Crops [4.9mb]

11th sequence APS-C mode 14 photos in 3-4 seconds full speed head on with a turn
Ratings (1,2,4,1,2,1,1,4,2,1,4,1,1,4)
50% perfect, 71.4% the camera did its job
Full Frame [5.6mb]
Crops [4.8mb]

12th and final sequence APS-C mode just 8 photos in less than 2 seconds head on, I'll award #1 ratings even if the camera transitioned to the other dog.
Ratings (1,2,1,1,1,1,4,1)
75% Perfect (even if it was tracking the wrong dog) 87.5% the camera did its job.
Full Frame [3.2mb]
Crops [2.9mb]

Over a spread of 12 sequences, 168 photos the camera got 44% perfect and 72.6% were the camera did as I believe it was supposed to. The camera is certainly far from perfect in this task but it can still provide dozens of good photos over a few short bursts. What is one to do with 74 effectively perfect action photos of their dog (ok and of other dogs too). In my opinion despite all the failures the keepers are well worth it.

Something I've known for a long time and maybe this will help others is that if the first photo in the burst is out of focus the camera will have a harder time re-acquiring focus and will definitely lead to fewer in focus photos in the sequence and a lower keeper rate. However I totally understand that unless you've got amazing eyes and a subject that is easy to see as in or out of focus it will be very hard to know if you're in focus when you start to burst. Another thing clearly demonstrated in these examples is as the subject gets too close the camera (most cameras) can't keep up anymore, if you're smart enough to stop shooting before they get too close your keeper percentage will be higher. The camera also does seem to fail when the Z-axis pace changes or the subject quickly changes direction, do you then fault it? after all it has no idea what the subject is or what it will do next.

So final thoughts... Take this evidence and make of it what you will, not every subject will produce the same results and its clear their is a wide range of results from just one subject. All in all YMMV and the K-1II is not as good as the competition is the most accurate description of its AF-C abilities. I suppose if its not good enough and you aren't willing to wait for better then just jump ship, if you're stubborn like myself keep enjoying shooting until better comes and then enjoy it just as much or more.

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Mike from Canada
"I am not a great photographer! God is a great creator! All I do is capture His creation with the tools He has provided me."
'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote :)'

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