With respect to post #10:
I find it easier to meter the projection through an empty carrier for maximum brightness to find the difference in stops. I use the aperture wide open for the brightest projection.
I first focus the smaller projection, remove the negative, replace the empty carrier, meter the center of the projection, and record the reading.
Then I replace the negative, resize the image, focus, remove the negative, replace the empty carrier, and meter as before. The difference in readings is Δf. Then the time factor is
The new exposure time is
Last edited by Ian C; 12-29-2012 at 12:14 PM. Click to view previous post history.