OP Home > Columns > Tech Tips > Cross With Purpose


Tuesday, June 19, 2012

Cross With Purpose

Reflecting On Reflections • The Triggertrap App • Stacked Converters • Autofocus At F/8

Labels: ColumnTech Tips
Stacked Converters

Q At a recent seminar, you mentioned using the 1.4X and 2X Canon tele-extenders together. I'm assuming that's done with an extension tube between them, or am I missing something?
J. Studwell
Via the Internet

A Different camera systems combine accessories in different ways. The method of stacking two tele-extenders together in the Canon camera system has changed over time. The original Canon EF tele-extenders wouldn't stack (mate), and a 12mm tube was placed between them to facilitate the technique. Interestingly, long teles like the Canon 300mm ƒ/2.8, 400mm ƒ/2.8, 500mm ƒ/4 and 600mm ƒ/4 would still focus to infinity with the 12mm tube in the light path. Then Canon came out with the improved 1.4X II and 2X II, which would stack without the need of the 12mm extension tube. Now Canon has made available the III series of tele-extenders, and they won't stack without the 12mm tube between them.

If you have trouble mating tele-extenders on other camera systems, try the extension tube. Be cautious, as pins on Nikon lens connections can be damaged when using extension tubes. I always carry a 12mm and a 25mm extension tube in my camera bag for closer focus and to use when certain combinations don't match due to a protruding rear element.

Autofocus At F/8

Q Will the new Canon EOS 5D Mark III autofocus through the full range of the EF 100-400mm f/4.5-5.6L zoom lens with the Canon EF 1.4X tele-extender?
G. King
Via the Internet

A All of the Canon "consumer-level" cameras (and, as awesome as it is, the 5D Mark III is included in this category) will autofocus only when the maximum aperture of the lens combination is ƒ/5.6 or larger (meaningƒ/5.6, ƒ/4, ƒ/3.5, ƒ/2.8 and so on). The professional cameras with the EOS-1 designation will autofocus up to an ƒ-stop of ƒ/8, except that the new Canon EOS-1D X won't autofocus to ƒ/8 and is regulated to ƒ/5.6 and larger.

The Canon EF 100-400mm ƒ/4.5-5.6L, 1.4X tele-extender and 5D Mark III combination won't autofocus because the 1.4X loses an ƒ-stop of light, making the maximum aperture of the 100-400mm zoom ƒ/6.3.

For information about upcoming seminars and digital-imaging workshops, visit www.georgelepp.com. If you have any tips or questions, address them to: OUTDOOR PHOTOGRAPHER, Dept. TT, George Lepp, 12121 Wilshire Blvd., Suite 1200, Los Angeles, CA 90025-1176 or online at www.georgelepp.com.


Add Comment


Popular OP Articles