[Nicholas Lindan]

I wonder if Nicholas could supply the magnification in the above examples.

The negative carrier size is 9.2mm. The projection of the carrier outline was measured, this contributes somewhat to the error as the carrier is 3 dimensional and the lens was focused on the negative in the middle of the carrier.

Going from a negative size of 9.2mm to the following sizes, the exposure factor correction in stops is:

Size......Magnification...Metered...Formula...DA Ruler
11mm ...1.2
21mm ...2.3...............1.1..........1.1.........1.3
32mm ...3.4...............2.0..........2.0.........2.0
45mm ...4.9...............2.8..........2.9.........2.8

The ruler and the formula should provide identical results as the ruler is based on the same optical formula - I am not sure where the discrepancy arrises at the 21mm image size. Apart from that they all seem to agree within experimental and rounding error.