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08-30-2015, 01:31 PM - 1 Like   #1
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C-AF challenge: K5II, XT-1, E-M1

As per a previous post, I've bounced around different camera systems and have developed a "standardized" test for C-AF. The subject is my 11-year-old daughter sprinting toward me from a similar spot on a sidewalk by our house. I have done this with my Fuji X-T1 pre and post Firmware 4 and Fuji's 55-200, the Olympus E-M1 and adapted Olympus 4/3 50-200 2.8/3.5 and today with my K5II and 60-250 lens. While CAF was my one minor complaint about my original K5II, that was with the 50-135. I don't know if the 60-250 is faster, but it seems to be. After today's test, I have no complaints with this combo - and am quite thrilled with the result. I can't wait to get a K3 and see how much more improved it is, although it would be hard to improve on these results.

First, the Olympus, done March 8, 2015. Firmware 3.0 for the E-M1was transformative, giving the Oly useable CAF. The best of two samples was 78% in-focus for the SWD lens version (this is an adapted lens from the legacy 4/3 system, the native 40-150 2.8 would be better). This sample had 42 frames in an 8 second burst, 33 images sharp. The original 50-200 without the faster SWD motor, gave me 45% in-focus rate.

Then to early June 2015 and to Fuji. My best keeper rate with the X-T1, in two runs, was 18% .... only 4 of the 22 frames in a short burst were sharp before Firmware 4.0 (a serious upgrade for Fuji). After upgrading to Firmware 4.0 on June 29, 2015 the results improved dramatically .... 76% sharp in a 21-frame burst: 16 sharp and 5 unsharp. First attempt was 63%, 22 sharp, 9 not sharp.

Now to August 30, 2015: Pentax K5II and 60-250. Two runs at me, on continuous high, zone focus C-AF and shooting jpeg. First burst, four seconds long, 20 frames shot. 100% sharp. Buffer filled and my 21st shot was three seconds later and out of focus. Second burst was 13 shots in two seconds before the buffer filled, also 100% in focus. Again, three seconds to the next shot and focus was lost.

A faster card (same card was used in all three cameras) and giving more time for the first burst to clear the buffer (I waited less than one minute between runs) would likely allow me a few more frames. Needless to say, I am quite happy with the results and find it a good comparison between systems using similar lenses. Olympus certainly has the deepest buffer and I would have had a better percentage of sharp photos with the native 40-150 2.8 lens, the IQ of the smaller m43 sensor isn't quite as good as the APS-C sensor in the K5II, especially at higher ISO's.

Attached image is a SOOC example

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PENTAX K-5 II  Photo 
08-30-2015, 01:40 PM   #2
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Impressive. Which settings did you use, and which focus point? I tested the K3's AF.C a couple of times and was not thrilled. With a subject coming towards me it would just not re-focus often enough to keep the subject in focus. I need to saw that I was shooting with a screw-drive lens (DA 35 f/2.4) in a relatively dark sports hall at a rather shallow depth of field (f/2.4) tough. I would love to have a try with the upcoming D FA* 70-200 f/2.8 in bright daylight.
08-30-2015, 01:47 PM   #3
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QuoteOriginally posted by jeffryscott Quote
As per a previous post, I've bounced around different camera systems and have developed a "standardized" test for C-AF. The subject is my 11-year-old daughter sprinting toward me from a similar spot on a sidewalk by our house. I have done this with my Fuji X-T1 pre and post Firmware 4 and Fuji's 55-200, the Olympus E-M1 and adapted Olympus 4/3 50-200 2.8/3.5 and today with my K5II and 60-250 lens. While CAF was my one minor complaint about my original K5II, that was with the 50-135. I don't know if the 60-250 is faster, but it seems to be. After today's test, I have no complaints with this combo - and am quite thrilled with the result. I can't wait to get a K3 and see how much more improved it is, although it would be hard to improve on these results.

First, the Olympus, done March 8, 2015. Firmware 3.0 for the E-M1was transformative, giving the Oly useable CAF. The best of two samples was 78% in-focus for the SWD lens version (this is an adapted lens from the legacy 4/3 system, the native 40-150 2.8 would be better). This sample had 42 frames in an 8 second burst, 33 images sharp. The original 50-200 without the faster SWD motor, gave me 45% in-focus rate.

Then to early June 2015 and to Fuji. My best keeper rate with the X-T1, in two runs, was 18% .... only 4 of the 22 frames in a short burst were sharp before Firmware 4.0 (a serious upgrade for Fuji). After upgrading to Firmware 4.0 on June 29, 2015 the results improved dramatically .... 76% sharp in a 21-frame burst: 16 sharp and 5 unsharp. First attempt was 63%, 22 sharp, 9 not sharp.

Now to August 30, 2015: Pentax K5II and 60-250. Two runs at me, on continuous high, zone focus C-AF and shooting jpeg. First burst, four seconds long, 20 frames shot. 100% sharp. Buffer filled and my 21st shot was three seconds later and out of focus. Second burst was 13 shots in two seconds before the buffer filled, also 100% in focus. Again, three seconds to the next shot and focus was lost.

A faster card (same card was used in all three cameras) and giving more time for the first burst to clear the buffer (I waited less than one minute between runs) would likely allow me a few more frames. Needless to say, I am quite happy with the results and find it a good comparison between systems using similar lenses. Olympus certainly has the deepest buffer and I would have had a better percentage of sharp photos with the native 40-150 2.8 lens, the IQ of the smaller m43 sensor isn't quite as good as the APS-C sensor in the K5II, especially at higher ISO's.

Attached image is a SOOC example
Interesting. K3 or K3ii definitely will be better ..
08-30-2015, 01:51 PM   #4
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QuoteOriginally posted by FantasticMrFox Quote
Impressive. Which settings did you use, and which focus point? I tested the K3's AF.C a couple of times and was not thrilled. With a subject coming towards me it would just not re-focus often enough to keep the subject in focus. I need to saw that I was shooting with a screw-drive lens (DA 35 f/2.4) in a relatively dark sports hall at a rather shallow depth of field (f/2.4) tough. I would love to have a try with the upcoming D FA* 70-200 f/2.8 in bright daylight.
I'm pretty sure most systems are gonna have an issue with those parameters, sans the big boys like the D4.

08-30-2015, 01:55 PM   #5
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QuoteOriginally posted by FantasticMrFox Quote
Impressive. Which settings did you use, and which focus point? I tested the K3's AF.C a couple of times and was not thrilled. With a subject coming towards me it would just not re-focus often enough to keep the subject in focus. I need to saw that I was shooting with a screw-drive lens (DA 35 f/2.4) in a relatively dark sports hall at a rather shallow depth of field (f/2.4) tough. I would love to have a try with the upcoming D FA* 70-200 f/2.8 in bright daylight.
Used the expanded AF and let it pick the point.
08-30-2015, 04:17 PM   #6
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Excellent experiment and observations. The moral of the story and the largest bang for the buck, is a substantially larger buffer. RAM is cheap (and this would be relatively slow for memory speeds), and it certainly does not use any additional real estate, and its power consumption is going to be minimal. Heat generation should not be substantially higher either. Pentax's engineers already have all of the part information. Re run the simulations and take another look at the analysis and find the new sweet point. It would be an additional comparison point (for marketing to use - I know Pentax does not have any marketing). If and when they finally get a new AF system, it's going to be necessary anyway. They already have the USBv3 and to couple it with the faster card manufacturers could be a new marketing avenue for both the card vendors and Pentax.

Pentax could easily enlarge the buffering to 10, 12 or even 15 seconds. At even 10 seconds few would complain. With 15 seconds of buffer - those who would complain, would be just whistling in the wind.

There is that analysis from the German magazine (from a few years ago) that showed that Pentax had a higher accuracy rate in focus lock. Couple that with this focus tracking and a substantially larger buffer, put out a white paper, and get a magazine / web site to demonstrate it - and push the envelope.


Last edited by interested_observer; 08-30-2015 at 04:25 PM.
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