03-16-2011, 09:31 PM
[quote name='Brightcolours' timestamp='1300307391' post='6885']
How did you calculate that? The 70 foot comes to 21 meters here (using a calculator as I am not familiar all that much with feet <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> ), and I can not, from the crops, determine 26 meters. A foot is 0.3048 meters.
The Toyota (IR) obviously was further away than the Lexus (BC), and that should help the Toyota crops in 2 ways: DOF is a bit deeper and the AF has it easier when a subject is further away.
But, on DOF, I shot with f4 (lens is not faster. This makes the AF having a harder time, though. I also am not entirely sure about the aperture used with the Sony... You can not actually choose the aperture, and if it is like with the video mode with AF, the aperture is actually set to f3.5. Which then does not make a big difference to f4.
All in all, I can not conclude, from the IR crop samples, that the A55v (and therefor the A33) have a very capable AF tracking implementation.
[/quote]
Well, it was rather approximate calculation - the size difference between the first crop and the last crop is 2.1x, so taking that car's speed was constant at 14 m/s and those frames were all taken in 1 second, you have to start approx in 26m from camera to make it look 2.1 times larger in 1 second (as it was tele lens used, it has to be fairly linear, or I'm wrong here?).
Regarding the aperture - bokeh fringing is quite apparent, so it has to be rather wide.
How did you calculate that? The 70 foot comes to 21 meters here (using a calculator as I am not familiar all that much with feet <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> ), and I can not, from the crops, determine 26 meters. A foot is 0.3048 meters.The Toyota (IR) obviously was further away than the Lexus (BC), and that should help the Toyota crops in 2 ways: DOF is a bit deeper and the AF has it easier when a subject is further away.
But, on DOF, I shot with f4 (lens is not faster. This makes the AF having a harder time, though. I also am not entirely sure about the aperture used with the Sony... You can not actually choose the aperture, and if it is like with the video mode with AF, the aperture is actually set to f3.5. Which then does not make a big difference to f4.
All in all, I can not conclude, from the IR crop samples, that the A55v (and therefor the A33) have a very capable AF tracking implementation.
[/quote]
Well, it was rather approximate calculation - the size difference between the first crop and the last crop is 2.1x, so taking that car's speed was constant at 14 m/s and those frames were all taken in 1 second, you have to start approx in 26m from camera to make it look 2.1 times larger in 1 second (as it was tele lens used, it has to be fairly linear, or I'm wrong here?).
Regarding the aperture - bokeh fringing is quite apparent, so it has to be rather wide.