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08-10-2010, 03:02 AM   #1
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Current Pentax AF.C Vs AF leaders

PENTAX AF.C Vs some competitors (tests done by labofnac)

Dynamic autofocus test

Subject speed 50 km/h (13,89 m/s)
Subject distance at starting track point 50 m
Equivalent focal lenght 200 mm
Lab. test with a simulator


Model Lens Total shots--Distance sharp shots--Distance Not sharp shots
Kx 80-200 f:2,8 IF ED 8 --49/45/38/31/26/22/16--7
D3000 80-200 F:2,8 D AF-S 6 --47/43/38/33/28/19
D5000 80-200 F:2,8 G 13 --48/44/41/37/34/30/27/
23/20/16/13/9--5
1000D 70-200 f:2,8 L IS 10 --45/41/35/31/26/22/17/
13/8/3
550D 70-200 f:2,8 G 11 --43/38/34/31/26/22/18/
14/10/6/2
K7 80-200 f:2,8 IF ED 8 --49/45/42/35/29/25--21/15

D90 80-200 f:2,8 D AF-S 10 --49/46/43/40/36/33/29/
22/15/8
D300s 80-200 f:2,8 D AF-S 23 --49/47/45/43/40/39/37/
35/32/30/28/26/24/22/
20/17/15/13/11/9/7--5/2
7D 80-200 f:2,8 L IS 21 --48/46/44/42/40/38/36/
34/30/28/25/23/21/19/
17/15/13/12/9/7--6
50D 70-200 f:2,8 L IS 21 --47/45/43/40/38/36/34/
32/29/27/25/22/20/18/
16/14/11/9/7/5/2


It shows that AF.C works fine when the subject is far than, let's say 15-25 meters, closer than that distance AF.C stack or don't work well.
Main competitors seems to have a better AF, especially at closer distance than 15-25 meters.

Hope it helps people concern with predictive autofocus issues.


Bye,

08-10-2010, 04:40 AM   #2
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This would read a lot better as a graphic or a table. I can't make head or tail of it all.

Eg the way US Popular Photography magazine measures AF speed is easier to read:

08-10-2010, 05:07 AM   #3
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The table you've post are AF.S. Mine is AF.C. The test that I'm taking consist in a target moving from 50 m towards the camera.
08-10-2010, 06:18 AM   #4
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Torrentes - thank you for posting the numbers. When shooting BIFs with AF.C your table makes a lot of sense. I have wondered about the accuracy when shooting a large bird flying towards me...now I know a little more than I used to. Thanks.

08-10-2010, 06:31 AM   #5
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Perhaps it becomes clearer after reading the original PDF file from fnac.
I've copied parts of the PDF for people interested.
It contains much more detail than AFC speed alone.

The link to the original file is here: Tests - essais - Photo numérique : Labo Fnac

Look at the diagram at the lower bottom corner at the right.
It contains the point in distance where the camera was in focus.
The in focus points are green, the out of focus point are in red.

This explains the test much better I think.
In this test the 50D is the best AFC performer.

First the Alpha 450 and K-x:
Name:  A450 Kx.jpg
Views: 1070
Size:  182.0 KB

Now the 550D and the K-7:
Name:  550D K7.jpg
Views: 1352
Size:  177.5 KB

The 500D and the D5000:
Name:  500D D5000.jpg
Views: 1232
Size:  176.7 KB

The D90 and the 50D:
Name:  D90 50D.jpg
Views: 1249
Size:  180.1 KB

The D300s and the 7D are here:
Name:  D300s 7D.jpg
Views: 1168
Size:  176.2 KB

- Cheers, Bert
08-10-2010, 07:56 AM   #6
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Interesting, but never trusted their tests very much. The 550D is indicated as much faster than the K7, but if you read carefully the numbers, it is not. The K-7, for example, shots earlier than the 550D focusing a human approaching, and is faster in the shot to shot timing. Well, ok, AFC is not the strong point of Pentax, we know, but four stars for the Canon vs two for the Pentax is just marketing, they got a better contract with the distributor.
08-10-2010, 10:25 AM   #7
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Marketng? I don't think that's the reason of my out of focus shots when I try to take a picture of krestels aproaching at my closer than 10-12 meters. With regard to the 4 star I think you're right.
08-10-2010, 10:45 AM   #8
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K-x vs K7

IIRC I think Popphoto also claims that the K-x to have better AFS than K7. Does anyone else have the Popphoto AF chart for K7 for comparison?

08-10-2010, 01:40 PM   #9
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QuoteOriginally posted by bymy141 Quote
...
Look at the diagram at the lower bottom corner at the right.
It contains the point in distance where the camera was in focus.
The in focus points are green, the out of focus point are in red.

This explains the test much better I think.
In this test the 50D is the best AFC performer.
- Cheers, Bert
Thanks for those images.
But I am confused.

In the fnac PDF (page 5) and in the images you've posted, the diagram at the bottom right indicates AF-S, not AF-C, for all of the camera's tested. And is explained as:
"Distance parcourue depuis le déclenchement en rafale à 50 m avec zoom 80-200 mm f:2,8 D AF-S"
Google translate:
"Distance traveled since the start gusting to 50 m with zoom 80-200 mm f/2.8 D AF-S".

Like they had the camera set of AF-S and just kept shooting on AF-S as the subject moved towards them, rather than having the camera set to AF-C proper.
08-10-2010, 03:30 PM   #10
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QuoteOriginally posted by rawr Quote
Thanks for those images.
But I am confused.

In the fnac PDF (page 5) and in the images you've posted, the diagram at the bottom right indicates AF-S, not AF-C, for all of the camera's tested. And is explained as:
"Distance parcourue depuis le déclenchement en rafale à 50 m avec zoom 80-200 mm f:2,8 D AF-S"
Google translate:
"Distance traveled since the start gusting to 50 m with zoom 80-200 mm f/2.8 D AF-S".

Like they had the camera set of AF-S and just kept shooting on AF-S as the subject moved towards them, rather than having the camera set to AF-C proper.
You need to translate the text below to understand the setup, however you are right.
They used AF.S in burst mode:

Autofocus dynamique
Le Labo Fnac a été le premier à disposer d’un banc de mesures capable de simuler le déplacement d’un sujet à n’importe quelle vitesse, de 0 à 300 km/heure, et n’importe quelle distance.
Nous l’avons programmé pour deux tests : le premier mesure le chemin parcouru par un enfant trottinant à 5 km/heure.
On déclenche quand il est à 5 mètres de l’appareil. La focale est équivalente à 80 mm en 24 x 36, bien adaptée à ce type de photo.
Pour le second, on déclenche à 50 m du sujet qui se déplace à 50 km/heure, avec focale équivalent à 200 mm. Mesures en position rafale, pour obtenir la distance parcourue pour la première photo, mais aussi combien l’appareil est capable d’en prendre, et à quel endroit. Et aussi combien sont nettes, ce que nous avons symbolisé par un code couleur dans le graphique résultat de chaque appareil.
08-10-2010, 03:33 PM   #11
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AF-S in the example in page 5 means Nikon lens called “80-200mm f:2,8 AF-S“
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