Posted by Larry Puckett on December 24, 2008 at 1:26 PM
Back in mu film camera days I used tele-extenders and close-up rings wiht my Canon equipment but so far have not experimented with them on digitals. I have been reading some messages that mention placing tape over the electrical contacts on cameras/lenses when using these with some Canon equipment. So what's the deal with using these? Are there certain lens and tele-extenders and close-up ring combinations that don't work without disabling the electrical connection? Are there some that jsut won't work at all? I know that the version II tele-extenders are compatible with both EF and EF-S lenses but are there certain lenses such as the 100-400mm that are not compatible with these? Thanks for the education--Larry
Posted by Randall Quon on December 24, 2008 at 2:18 PM
Tele-extenders & extension tubes work the same on digital as on film cameras. Some film and digital cameras won't autofocus with lens+tele combos having a max aperture equal to or smaller than f/8. The tape blocks the signal so that the camera thinks that the max aperture is whatever the lens' is and will allow autofocus (but slower because of the loss of light).
Posted by Tom Smit on December 25, 2008 at 5:25 AM
As Randal wrote, the tape is just to fool the camera if you use original Canon equipment.
The canon extenders can only be used on several lenses.
Non canon extenders also seems to work on other lenses (never tried because I do not have such a exender), You can read enough about it on the net.
Good luck.
Posted by Larry Puckett on December 25, 2008 at 10:43 AM
Basically then the drop in light prevents the autofocus from working so it just hunts and burns up the battery? Covering the contacts disable the autofocus so this doesn't happen? Guess I'll have to do some googling to see which combinations of lenses do and don't work with this--Larry
Posted by Randall Quon on December 25, 2008 at 3:11 PM
The drop in light decreases AF performance; Canon chose to disable AF (edit: depending on the resulting aperture). Covering the contacts enables AF.
For example, a 20D won't AF with a 1.4x tele-ext and the 100-400 lens. Taping the pins allows AF. When looking for what combinations work, you have to include the lens, teleconverter, and the body (AF sensor).
The Canon teleconverters have optics that protrude and are compatible (physically) with Canon lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, 70-200 f/4.0L IS USM, and 100-400 f/4.5-5.6L IS zoom lenses. The non-Canon teleconverters don't have protruding elements and are compatible with any lenses.
Discussion
4 repliesThe canon extenders can only be used on several lenses.
Non canon extenders also seems to work on other lenses (never tried because I do not have such a exender), You can read enough about it on the net.
Good luck.
For example, a 20D won't AF with a 1.4x tele-ext and the 100-400 lens. Taping the pins allows AF. When looking for what combinations work, you have to include the lens, teleconverter, and the body (AF sensor).
The Canon teleconverters have optics that protrude and are compatible (physically) with Canon lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, 70-200 f/4.0L IS USM, and 100-400 f/4.5-5.6L IS zoom lenses. The non-Canon teleconverters don't have protruding elements and are compatible with any lenses.