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Obtaining "focus distance" from a Canon SLR

Greetings, this is a rather abititious question but some might enjoy the challenge.

I am looking at writing some software (using the Canon Digital Camera Software Development Kit) for a pan & zoom application. For this particular application to work best, I will need to get the "focus distance" by fair or by foul. The good news for all you enthusists, I have no problem hacking apart a camera (most likely a second hand D10 or D60) to acheive the goal.

Now I understand that Canon SLR's do not electronically record this information (although other manufacturers do, they don't have an SDK like Canon) which rules out the fair way. So what I would like to know is how I could hack out the focal distance by foul so it can be read into a computer (through a data acquisition card). I should point out, I do not need an accurate measurement. A ball-park figure would almost do.

I can really only think of two possible ways of extraction. Either by placing a probe where the auto-focus is transduced into an electrical value. The other is by painting a sequence of codes around the manual focus ring for sesnor to read.

Any ideas, pointers, suggestions or insults are welcome. :-)

kwijibo
Tue, 05 Sep 2006 05:01:10 -0700

There may be a way to accessthe focus distance info via the flash circuitry. When using an external flash, the flash`s display does give an exposure range distance. This might be helpful for you.

Scott
Thu, 07 Sep 2006 23:23:49 -0700

^ Thanks for the tip. I actually don't own a proper flash at this point in time, although I may be able to borrow one to so I can investigate your idea.

Keep them ideas coming if you can.

Cheers

kwijibo
Wed, 13 Sep 2006 06:27:32 -0700

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