Subject:	Now you're getting into a tough area.
Author:	drdread
Date:	10/15/2001 12:46:43 PM
Message:

This is a perennial question. You might ask over on the uw-photo mailing list, as many people have asked this question and many others have already solved the problem.

That said, the best thing to do is going to be to do the experiment yourself. The expt. will have to be done in two phases. First, find the focal distance. This can be done by taping a ruler to the front of the extension tube setup, sticking straight out but with a slight upward angle. Take a picture with this setup and then examine the resulting slide to find the place on the ruler that is in sharp focus. That's your focal distance. Then attach a piece of paper at the exact focal distance, with diagonal lines radiating from the cener point. Mark the lines like you would mark a ruler. Take another picture, and the resulting frame will tell you what the field of view will be.

Finally, if you really want to try to calculate all this, try looking at this web page: www.reefnet.on.ca/gearbag/ as they have lots of interesting calculations to share...

Good luck,
D

Subject

Author

Date

Focal distance and picture area for extension tubes (1)

Thomas Wernberg

10/14/2001 10:07:03 PM

Now you're getting into a tough area. (0)

drdread

10/15/2001 12:46:43 PM

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