AF with 1.4 extender's pins taped

[Alan]

I tried this technique http://www.michaelfurtman.com/taping_the_pins.htm and it works to restore the AF on my 100-400 and 300 f/4.


It's a bit slow to AF, but it does settle down.


But, something that I didn't expect was the extender didn't affect the aperture setting.


The 100-400 still showed f/5.6 at its longest length and the 300 f/4 still showed f/4. I took a couple of shots from each lens and the file info confirms it.


I thought that this technique could over ride the AF, but I didn't think it would keep the aperture from changing to a smaller number.

[Wes]

Alan that is the reason it works when they are taped because it isn't reporting the combined aperture. You shouldn't need to have it taped on the 300 though since even with the TC you are still just at 5.6 and normally only cameras that wont AF with F\8 as a starting aperture needs to have the pins taped. I use a 1.4TC all the time on mine without any problems. The way I understand it would only need to be done on F\5.6 lenses and above.

[neuroanatomist]

But, something that I didn't expect was the extender didn't affect the aperture setting.


The 100-400 still showed f/5.6 at its longest length and the 300 f/4 still showed f/4. I took a couple of shots from each lens and the file info confirms it.

The aperture is affected. That's physics. The reason the file info 'confirms' that the aperture is not affected is the same reason autofocus works - the tape blocks the pins that transmit aperture data to the lens. The camera 'doesn't know' that the 100-400mm is at f/8, so it 'assumes' the lens is f/5.6 based on stored lens data for that focal length. It autofocuses accordingly and stores that (incorrect) EXIF data with the image.

[Alan]

The aperture is affected. That's physics. The reason the file info 'confirms' that the aperture is not affected is the same reason autofocus works - the tape blocks the pins that transmit aperture data to the lens. The camera 'doesn't know' that the 100-400mm is at f/8, so it 'assumes' the lens is f/5.6 based on stored lens data for that focal length. It autofocuses accordingly and stores that (incorrect) EXIF data with the image.
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That makes sense. Thanks for clarifying.