Canon Japan EOS-1D X The Birth of Entirely new Flagship

[dougkerr]

Hi, CT,

Yes, I know...but Doug stated, in effect, that at lens apertures narrower than specificed for the AF system, i.e. f/5.6, the AF detetors cannot function at all, i.e. it's an optical limitation, as opposed to a firmware limitation. The fact that an f/6.3 lens can AF, as can an f/8 lens under certain conditions, with an f/5.6-sensitive sensor, suggests that it's a firmware limitation, and not an optical limitation.

Well, the pupils have a certain size, and at f/5.6, they're not shaded at all and the focus sensors get the full amount of light. But when you attach a slightly slower lens as f/6.3 they start to get shaded, but there's still light coming thru to the sensors. So it works worse in low-light conditions. As people report here, the pupils are nearly fully covered at f/8 depending on the lens. This is why it may still work with a lot of light.

And the body may in fact let the AF system (try to) work at a reported aperture of f/6.3. But not f/8

Best regards,

Doug

 

[dougkerr]

Hi, N,

AFAIK, the Tamron and Sigma lenses send false information (read: that the aperture is at f/5.6 when it's actually f/6.3)

Yes, I know...but Doug stated, in effect, that at lens apertures narrower than specificed for the AF system, i.e. f/5.6, the AF detetors cannot function at all, i.e. it's an optical limitation, as opposed to a firmware limitation. The fact that an f/6.3 lens can AF, as can an f/8 lens under certain conditions, with an f/5.6-sensitive sensor, suggests that it's a firmware limitation, and not an optical limitation.

The fact that the camera will not allow the AF system to attempt to work below a certain aperture is a firmware limitation.

The fact that it will not work (or work well) below a certain aperture is a hardware (optical) limitation.

As others have pointed out, the latter is not "knife-edge". If we can force the camera to "let the AF work" at an aperture of, for example f/8 (for an "f/5.6" AF detector). it may work with some difficulty. At f/6.3 it will likely work "pretty well".

Best regards,

Doug

 

[Loswr]

That's what I thought, Doug, but expert confirmation is always appreciated!

Best,

John