Close-up, Macro, Micro Calculations

[Corran]

Something that I read on this forum, and is much easier for me, is to simply take the total extension from the center of the lens (non-tele) when focused and divide it by the absolute aperture size (lens focal length divided by f/stop). This gives the "corrected" aperture, which you can use for exposure calculation, or if you want to shoot at a given aperture, you can easily convert in the opposite direction.

IMO, faffing about with the magnification is overly complicated, but that's just me. Unless you have to have a specific magnification for scientific applications or something.

[ic-racer]

IF I KNOW THE MAGNIFICATION, HOW DO I DETERMINE THE AMOUNT TO ADJUST THE f-STOP????

stops = log((1+M)2)/log(2)

That is clever you tried to figure it from the curve fit, but you used the wrong curve fit. Maybe your software did not give you enough different choices.

[Dan Fromm]

stops = log((1+M)2)/log(2)

That is clever you tried to figure it from the curve fit, but you used the wrong curve fit. Maybe your software did not give you enough different choices.

Hmm. I posted that some time ago.

[xkaes]

stops = log((1+M)2)/log(2)

That is clever you tried to figure it from the curve fit, but you used the wrong curve fit. Maybe your software did not give you enough different choices.

The software I used (SPSS) offers over a dozen approaches/formulas -- and tests each for significance. I applied them all. One of them is logarithmic, quadratic, etc. but the best fit to the curve, by far, was cubic. But as I showed, it's close, but not as close as I would like. I have some other "curve fit" software that I can fire up as well, but I doubt that they have more options than SPSS.

Thanks for the formula. I'll give it a try.

[xkaes]

stops = log((1+M)2)/log(2)

That is clever you tried to figure it from the curve fit, but you used the wrong curve fit. Maybe your software did not give you enough different choices.

Do you mean:

stops = log((1+M)²)/0.30102999566

or something else?

[Ken Lee]

Some of the formulas are the same, but you might find this short article helpful: Formulas for Bellows Extension and Compensation

It's written for view camera dummies, by a view camera dummy :-)

[xkaes]

Some of the formulas are the same, but you might find this short article helpful: Formulas for Bellows Extension and Compensation

It's written for view camera dummies, by a view camera dummy :-)

Thanks. That's not exactly what I was looking for -- it's BETTER than what I was looking for.