Canon 1.4x - Report the *focal length* to the camera body?

[s._misra]

Hi.

 

It is well known that by taping the last three pins on the Canon

1.4x teleconverter, the converters effect on aperture is *not*

reported back to the camera body. This allows the autofocus function

to be retained in situations where it would otherwise be lost.

 

My question is, is there anyway to still have the *focal length* or

another identifying characteristic reported back to the body? I am

using a digital Canon 10D camera. The problem is that when I review

my images, I cannot tell which images were taken with the converter

and without the converter, since none of this info is reported back

to the body.

 

Thanks.

[isaac sibson]

Remove the tape.

[s._misra]

Hi.

 

I am not sure if you are being humorous or if my original post was unclear. Let me clarify:

 

I don't want the teleconverter to report back the aperture (if it did, I would lose autofocus), but I do want it to report back something that I can use to identify the images in which the teleconverter was used (e.g., the overall focal length, etc..). Does anyone know a way to do this?

[isaac sibson]

No, because it's part of the same process. If you want the FL reported correctly then you have the aperture reported correctly also. On your 10D this may mean you lose AF, but canon have put that restriction in place because the 10D's AF system is not reliable at that aperture.

 

So my response might have seemed off-hand or sarcastic, but it is the way to do it. Otherwise you can manually record the use of the TC.

[bobatkins]

Which lenses do you find this trick works with? I once tried it with a 500/4.5L and Elan II and all the lens did was hunt for focus forever or when it got near focus it would oscillate back and forth around the correct focus point.

 

I've seen this trick reported to work in a number of places - and I even worked it out for myself about 10 years ago - however I've never managed to find a lens/body combination it was actually usable with. AF was never reliable and as often as not it would never find focus.

 

In the end I always found that manual focus was much more reliable, if a little slower at times.

[s._misra]

Hi Bob.

 

I was trying this "trick" with the Canon D10 + 400 5.6L + 1.4x.

 

In truth, your obersvations are/were accurate. The AF is unreliable -sometimes it hunts, sometimes it locks incorrectly, sometimes it works very well..and I tested under fairly AF-friendly conditions (moderate constrast, bright light).

 

Saswat