I wanted make a brief post to mention this information that was pointed out to me by my friend Colby Brown.  It used to be the case that only Canon 1-series cameras could focus with lenses with a minimum aperture of f8.  It was a feature that set them apart and above the rest of the lineup, albeit only the center AF point worked.  Now Canon doesn’t manufacture any lenses that have such a small minimum aperture natively but there are plenty of ways to get there by using extenders.

The newly announced Canon EOS-1D X (their new flagship!) DOES NOT allow AF with f8 lenses.

This isn’t something that Canon mentioned anywhere on launch day as far as I could see, I’m sure it will be in the fine print of the manual eventually but it might make a difference to some people so I wanted to draw attention to it.  With the fancy new AF system that they are making so much fuss about I can’t wrap my head around why they would remove this feature from a camera!

Popular combinations that this will affect:

Canon 800mm f5.6 L IS + 1.4x Extender

Canon 70-200 f4  L IS + 2x Extender

Canon 500mm f4 L IS I & II + 2X Extender

Canon 600mm f4 L IS I & II + 2X Extender

Canon 400mm f4 DO IS + 2x Extender

Canon 300mm f4 L IS + 2x Extender

Canon 400mm f5.6 L + 1.4x Extender

Off the top of my head these are the combination that are going to be most affected.  In particular bird photographers use several of these combos to reach longer lengths at more reasonable price points.  Art Morris received this response from Canon’s Chuck Westerfall regarding this:

“AF is unavailable on the EOS-1D X if the maximum aperture reported to the camera through the electronic lens mount is smaller than f/5.6. This is a lower specification than previous EOS-1 series DSLRs. On the plus side, consider the fact that with most f/4 lenses including the 400 DO, 500/4L IS and IS II, and 600/4L IS and IS II, you now have 41 cross-type AF points plus color and face detection, whereas you had no cross-type points and no color or face detection during AF with previous EOS-1 series DSLRs using the same lenses, not to mention a significantly wider AF coverage area from left to right.”

There’s no doubt that it will be nice to have 41 cross type sensors for f4 lenses, that will dramatically increase focus accuracy and tracking but Mr Westerfall doesn’t disclose a good reason for the downgrade in specification.

Canon 200-400 f4 L IS

I think this information also answers a question that many people were wandering about the upcoming 200-400 f4 L IS USM Extender 1.4x.  The yet to be released lens features a built in 1.4x extender which can be operated with the simple flick of a switch.  The fact that the optics are built into the lens and therefore optimized for that particular lens means that optically it’s likely to perform VERY well with the extender implemented, giving a good 560mm f5.6.  Many people were excited about the possibility of adding the new 1.xx MKIII extender to this lens to reach nearly 800mm but with presumably slightly less degradation in quality than a 2x extender would normally impart on a 400mm lens.

Given that this combination, with both internal and external 1.4x extenders would produce a minimum f8 aperture it will now not focus on any Canon DSLRs moving forwards.  We still don’t know if it would be physically possible to use the external 1.4x anyway but it’s now going to be a moot point for people who want to move to the 1D X anyway.