08-03-2011, 08:56 AM
[quote name='popo' timestamp='1311981807' post='10324']
I just had an idea that might be a little crazy, but I think might be worth a try.
Does anyone know their filter gel characteristics? I'm looking for one that passes red and blue, but blocks green. Something like Congo Blue is close, but that passes blue and IR. If there's one that shifts the red range up a bit that will be ideal.
Why do I want this? I wonder what the DSLR phase AF sensors are like to colour? I have to assume they're somewhat panchromic otherwise they wouldn't work with some monochromatic targets. I suspect that for a lot of "near misses" I get with tracking AF of smaller or darker subjects, the AF system is picking green items nearby in preference. If I can slide in a gel to modify the AF response (possibly needing minor offset correction) that might help.
[/quote]
I'm not sure about other systems but in the latest Nikon DSLRs AF and metering work hand in hand for specific combinations. For example auto area mode gets the color information (e.g. the skin tone) from the metering module and uses it for correct choice of focus point(s). Also, dynamic area AF (AF tracking) is assisted by the metering module regarding the changes in color patterns to determine the movement of the subject.
But when it comes to single point AF, I'm not sure if the AF module utilizes the color information. Though, the luminance, shape, pattern and the size of the objects are definitely important for a precise AF.
Serkan
I just had an idea that might be a little crazy, but I think might be worth a try.
Does anyone know their filter gel characteristics? I'm looking for one that passes red and blue, but blocks green. Something like Congo Blue is close, but that passes blue and IR. If there's one that shifts the red range up a bit that will be ideal.
Why do I want this? I wonder what the DSLR phase AF sensors are like to colour? I have to assume they're somewhat panchromic otherwise they wouldn't work with some monochromatic targets. I suspect that for a lot of "near misses" I get with tracking AF of smaller or darker subjects, the AF system is picking green items nearby in preference. If I can slide in a gel to modify the AF response (possibly needing minor offset correction) that might help.
[/quote]
I'm not sure about other systems but in the latest Nikon DSLRs AF and metering work hand in hand for specific combinations. For example auto area mode gets the color information (e.g. the skin tone) from the metering module and uses it for correct choice of focus point(s). Also, dynamic area AF (AF tracking) is assisted by the metering module regarding the changes in color patterns to determine the movement of the subject.
But when it comes to single point AF, I'm not sure if the AF module utilizes the color information. Though, the luminance, shape, pattern and the size of the objects are definitely important for a precise AF.
Serkan