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02-25-2019, 12:29 AM - 5 Likes   #1
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One of very, very few repeatable AF.C autofocus tracking tests

The German magazine" c't Digitale Fotografie 02/19" just published another AF.C autofocus test comparison.

While 99.9% of what is written about autofocus on the internet not even reaches elementary school scientific quality the testers here did set up some scenarios which could be reproduced technically 100%, so results are relevant and say a lot (within the boundaries tested).

They did set up contrasty Lego toy trains in good light and shot them as they were coming at the camera in various angles and with various items block sights.


I will not invest the effort to describe more details, just the results. Who really cares has to buy the magazine/article: Autofokus im Praxistest | c't Digitale Fotografie | Heise Magazine


Again the results are telling a lot about the credibility, skills and brains of users who claim "near 100% autofocus hit rates" on the net for their loved gear. They seem to shoot brick walls only.

It also shows that even within a group of relatively similar scenarios, the relatively best camera can change. So overarching general statements which gear is best are nonsense all the time.





Obviously all cameras struggled quite a bit.

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02-25-2019, 01:42 AM   #2
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The Fuji XT-3 has 425 PDAF points on its sensor for nearly 100% coverage.

Correlation with its performance on the test is shown by this data to be poor, especially compared to the DSLR.
02-25-2019, 03:37 AM   #3
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QuoteOriginally posted by clackers Quote
The Fuji XT-3 has 425 PDAF points on its sensor for nearly 100% coverage.

Correlation with its performance on the test is shown by this data to be poor, especially compared to the DSLR.
It does appear that there is something still to be said for having a dedicated auto focus sensor rather than having auto focus points on the sensor. The D500 does appear to outperform the mirrorless options in this test.
02-25-2019, 03:55 AM   #4
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QuoteOriginally posted by clackers Quote
Correlation with its performance on the test is shown by this data to be poor, especially compared to the DSLR.
On the DSLR, the PDAF sensor works while the mirror is down and the image sensor unload the image into memory.
On the mirrorless camera multiple image frames are acquired for PDAF prediction and also capturing images that are in focus for the camera user (time sharing of the image sensor resource).
But the MILC is cheaper to build, single sensor, no mechanical actuation, and more simple to operate than DSLR.

02-25-2019, 06:04 AM   #5
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QuoteOriginally posted by Rondec Quote
The D500 does appear to outperform the mirrorless options in this test.
In three out of five cases yes. In the two others (#2 and #3) it underperforms.

#2: Training coming straight at the camera, distracting moving objects cross in front of it.
#3: no tracking really, just panning, following the train from right to left in front of distracting background
02-25-2019, 06:23 AM   #6
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Full marks for setting up a repeatable test, but I have to ask how relevant is this for common shooting situations? Lego trains are pretty small and I assume fairly close?

How did they classify shots as focus nailed, failed somewhat, and failed completely? I'm genuinely curious, I'd be interested in (hopefully free) software that can objectively assign some kind of sharpness value to a photo or parts of a photo (like after the fact focus peeking).
02-25-2019, 06:46 AM   #7
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I find that fascinating insofar as it is abundantly ckear that no camerais best in all scenarios, and the D500 is brilliant atsome and rubbish at others - ie no one test gives a reliable picture od a cameras capability
02-25-2019, 07:03 AM   #8
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Somehow that's what I always suspected. Tracking AF is still largely irrelevant to my shooting. That it is far less accurate than AF.s, which is well over 95% is one of the best kept secrets in photography. Bottom line, if you can get the shots you want with AF.s you are still ahead of the game, by a considerable margin.

02-25-2019, 08:54 AM   #9
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QuoteOriginally posted by BrianR Quote
How did they classify shots as focus nailed, failed somewhat, and failed completely?
All scenarios had the requirement to focus on the tip of the locomotive leading the train with all waggons. "nailed" was focus correctly on tip of the train. failed somewhat means focus hit the locomotive but not the tip of it. failed completely means the lcocomotive was not in focus at all.

In the magazine there is a pretty detailed explanation with smaple images and sketches of the setup to explain what was done.
02-25-2019, 11:31 PM   #10
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Fast AF tracking performance is for gear focused photographers. If AF tracking was a must, there would be zero market for medium format. Evidence shows that the best professional photographers don't use AF tracking. And a lot of people who seek high AF tracking performance have money but no talent, unfortunately.
02-26-2019, 02:00 AM - 1 Like   #11
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QuoteOriginally posted by biz-engineer Quote
Fast AF tracking performance is for gear focused photographers. If AF tracking was a must, there would be zero market for medium format. Evidence shows that the best professional photographers don't use AF tracking. And a lot of people who seek high AF tracking performance have money but no talent, unfortunately.
I suspect after a point this is true. A little bit of this does work wonders for a friend who has essential tremors and grandchildren. The gx85 Panasonic has good tracking which has made him more able to capture special moments. He is no pro that is true, but he is very very happy that this camera does this reasonably well. But after a point the differences in ability seems like "measurbating".
02-26-2019, 03:21 AM   #12
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QuoteOriginally posted by UncleVanya Quote
A little bit of this does work wonders for a friend who has essential tremors and grandchildren.
For tremors I would tend to believe that SR help more than af tracking.
02-26-2019, 04:06 AM   #13
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QuoteOriginally posted by beholder3 Quote
In three out of five cases yes. In the two others (#2 and #3) it underperforms.

#2: Training coming straight at the camera, distracting moving objects cross in front of it.
#3: no tracking really, just panning, following the train from right to left in front of distracting background
I guess I'm more thinking about the D500 versus the XT-3. The other two have smaller sensors and therefore have a bit more depth of field to play with in test situations. My i phone focuses pretty fast, but that's because it doesn't really have to focus...
02-26-2019, 08:51 AM   #14
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QuoteOriginally posted by Rondec Quote
I guess I'm more thinking about the D500 versus the XT-3. The other two have smaller sensors and therefore have a bit more depth of field to play with in test situations. My i phone focuses pretty fast, but that's because it doesn't really have to focus...
I am just making assumptions, but I guess that even with 1 inch at F4 at these close distances it is pretty easy to judge if the AF hit or not. Yes, there will be more DoF, but it probably did not influence their judgement.
02-26-2019, 10:59 AM - 1 Like   #15
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QuoteOriginally posted by biz-engineer Quote
For tremors I would tend to believe that SR help more than af tracking.
Both help, the inability to keep the camera pointed directly at the subject is where fancier tracking options helped him. Also the movie capture modes work wonders when kids are scrambling about - at least for him.

The tech advances are a boon to some people, but most of us really don't require them. I frequently feel like users are spoiled by the level of sophistication of modern gear.
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