I have an elan 7e and read somewhere that with large apertures some of the focus points don't work. Is this true? And if it is: is canon trying to sell me an eos 3?

-- marc brackhahn (pookeybookey@aol.com), April 09, 2002

Answers

With large apertures (smaller number), all focus points on the EOS 30 (elan 7e) will work. With apertures below F5.6 (larger numbers than 5.6), the AF will not work.

The EOS 3 and EOS 1V (and 1D) are capable of AF at F8 on the centre focus-point with a single axis only. At F4 and faster, the centre point becomes Cross-type and high-precision. The EOS 30's centre point is cross-type at F5.6 and faster, but always at normal precision. Slower than F5.6, and it is not functional. It has no single-axis mode.

-- Isaac Sibson (isibson@hotmail.com), April 09, 2002.

Isaac's first comment is a little misleading.

What he means is, if the maximum available apperture on the lens is greater than f5.6 AF won't work. If you put an f5.6 lens on AF works fine. Also, if you put an f5.6 lens on, and stop down to f8, f16, even f32 AF will still work, as the lens doesn't close down until you hit the shutter (or DOF preview) button.

But, if you had your f5.6 lens and slapped a 1.4 teleconvertor on it you've just made it into a lens capapble of no better than f6, and you'll lose Autofocus.

And yes, as far as I'm aware (as an Elan 7e owner) all the points work at all appertures.

-- Marcus (Citizensmith@lanset.com), April 09, 2002.

"What he means is, if the maximum available apperture on the lens is greater than f5.6 AF won't work. "

I think what Marcus meant to say is "if the maximum available aperture on the lens is less than f5.6 (e.g., F6.7, F8), AF does not work."

In the case of aperture, a larger number means a smaller hole and, therefore, less light.

Aloha

-- Puppy Face (doggieface@aol.com), April 09, 2002.

The only time this will be a problem is when you use a teleconverter. For example, if you use a Canon 70-200/4L with a 2x teleconverter, it becomes a 140-400/8L. With the lenses maximum aperture of f/8, the camera will lose autofocus. This DOES NOT mean that when using the 70-200/4L alone you lose autofocus when stopping down to f/8. Autofocus cameras always autofocus when the lens is wide open. It is only when you take the picture does the lens actually stop down to f/8 (or when using depth-of-field preview, during which you aren't autofocusing anyway).

-- Peter Phan (pphan01@hotmail.com), April 11, 2002.

To add a little more, I would say that all original EF lenses from Canon will work on any EOS body, unless either of them is malfunctioning.

-- sajeev (chack74@yahoo.co.in), April 12, 2002.