Re: Canon 5D Focus Hunting in Low Light

"David J. Littleboy" <davidjl@xxxxxxx> wrote in
news:6qSdnR3imYIET3zanZ2dnUVZ_gGdnZ2d@xxxxxxxxxxxx:


"Ray Paseur" <Ray.Paseur@xxxxxxxxxxxxxxxxxxxxxx> wrote:

Canon users: Here is my experience with the 5D. I'd like to see if
you have a similar observation.

I find the camera to fall into an endless cycle of focus-hunting in
low light if the ISO is set at, say, 100. By "low light" I mean
modeling lights in studio or stained glass windows on an overcast day
-- good contrast but not much candlepower.

But if I set the ISO to 800, the focus is lighting fast and accurate.
This makes me wonder if it would have been possible to design the
camera to
try its focus, and if it failed then switch to the next highest ISO,
retry focus, etc. When the focus is fixed, it would seem
programatically able to
return to the original ISO setting for the image capture.

I'm not able to reproduce that. (And it makes no sense. The ISO
setting sets the amplification applied to the signal from the sensor
and is unrelated to the AF/AE systems.) With the lens at hand (Tamron
28-75/2.8) and low room light, AF works the same whatever I set the
ISO to. The things it can and can't AF on are identical, as is AF
speed. With the 50/1.4, it focuses in light that's too dark for me to
see.

David J. Littleboy
Tokyo, Japan


Thanks David. To clarify, I am using the Canon brand 24-105 f/4 mostly
and it is specifically what I referred to in this experience. I have
the 50/1.4 and will try it in low light at different ISO settings. ~JRP

.

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