Taping The Pins

 

In several articles on my website, I refer to "taping the pins" when using the 1.4x tele-extender on a lens. Several readers have asked what I mean by that phrase, so I guess it is time to explain!

On Canon cameras (other than the "1" series pro-bodies), autofocus is lost when using an extender on a lens that has a maximum aperture greater than f/4. For instance, my favorite lens, the 100-400 f/4.5-5.6 will not function with a tele-extender except as a manual focus lens.

I really don't know why Canon does this, as autofocus WILL work, albeit somewhat slowly, as is proved by the fact that you can tape three pins on the extender and restore autofocus function.

These pins, located on the side of the extender that FACES the lens, are part of the communication system between lens and body. All one need to do is place a very small piece of tape over the pins, and autofocus is restored. Regular "transparent" (otherwise known as "Scotch") tape works just fine. I once used a piece of a band-aide! The kind of tape really doesn't make any difference, as long as it isn't so thick that it keeps the uncovered pins from making good electrical contact.

Here's a photo of the proper placement of the tape:

Photo Courtesy of Fred Miranda

This modification works well on the 1.4x extender, but does NOT work with a 2x version. As I mentioned above, focus will be a bit slow, and in poor light, the lens may "hunt" until it locks on the subject. I've found that I can use this arrangement even on birds in flight, however the light conditions must be good, and the birds relatively slow moving species. On stationary or slow moving subjects, focus will be just fine.