Will the IS continue to work ,on the 100-400 L, if I use a 1.4 canon extender ? I realise I will lose AF with the Elan IIe .

-- D.C. (dmconnell@charter.net), December 14, 2001

Answers

With the Elan IIe, IS will indeed still function with the extender. Only with older bodies (Pre EOS-1N) does IS not work at smaller apertures (below F5.6).

-- Isaac Sibson (isibson@hotmail.com), December 14, 2001.

im just wondering why it wouldn't work with pre eos 1n cameras? isn't the IS on the lens independent of the camera?

-- Jeff Nakayama (moonduck22@hotmail.com), December 15, 2001.

I'm not sure why, but that appears to be the formula for working it out...if the aperture drops below F5.6 with the older bodies, IS is cut off.

My guess is that the IS and AF systems take their power through the same pins, and the control goes through the other pins. The older cameras perhaps cut off AF by cutting the power, but then Canon realised they needed the power for IS, and so started to design that in (The 70-300 IS was on the drawing board at the same time as the EOS 1N). That would explain why it cuts off at the AF cut-off aperture. This is just a guess.

-- Isaac Sibson (isibson@hotmail.com), December 15, 2001.

IS works with EOS-1 + 1.4 extender + 4/300L IS. No idea about other older cameras, I just tried this combination and it's working but hard to auto focus because of f5.6!

-- Martin (uboot67@yahoo.com), December 18, 2001.

Indeed it should work. However, if you were to put a 2X TC onto that lens on the same body, then the aperture drops below F5.6 to F8, and IS will cut out. On my EOS 5, my 300 F4L IS + 1.4X TC works fine, but when I try the 100-400 with the 1.4X TC, IS and AF are lost.

-- Isaac Sibson (isibson@hotmail.com), December 19, 2001.