> > 1. How would an individual, without any
formal technical
> > training, actually test this with a particular lens?
> > training, actually test this with a particular lens?
You can't do it "easily" -- not without some equipment.
And, about the f-stop calculation ...
Here's a table of whole and half f-stops. Note that 1 and 1/2 stops
loss from f/22 is f/38 ...
| relative | f | whole / |
| exposure | number | half |
| 1.00 | 1.00 | whole |
| 1.41 | 1.19 | half |
| 2.00 | 1.41 | whole |
| 2.83 | 1.68 | half |
| 4.00 | 2.00 | whole |
| 5.66 | 2.38 | half |
| 8.00 | 2.83 | whole |
| 11.31 | 3.36 | half |
| 16.00 | 4.00 | whole |
| 22.63 | 4.76 | half |
| 32.00 | 5.66 | whole |
| 45.25 | 6.73 | half |
| 64.00 | 8.00 | whole |
| 90.51 | 9.51 | half |
| 128.00 | 11.31 | whole |
| 181.02 | 13.45 | half |
| 256.00 | 16.00 | whole |
| 362.04 | 19.03 | half |
| 512.00 | 22.63 | whole |
| 724.08 | 26.91 | half |
| 1024.00 | 32.00 | whole |
| 1448.15 | 38.05 | half |
| 2048.00 | 45.25 | whole |
| 2896.31 | 53.82 | half |
| 4096.00 | 64.00 | whole |
| 5792.62 | 76.11 | half |
| 8192.00 | 90.51 | whole |
| 11585.24 | 107.63 | half |
| 16384.00 | 128.00 | whole |
> > 3. How would one "calculate for diffraction"?
About the diffraction limit: Too complex to talk about in
email. Just know that, as Andy said, there is a tradeoff point
between overall optical performance and "Depth of field". The
problem is that the diffraction limit isn't dependent on FL, but only on the
wavelength of the light and the F-stop chosen. This immediately generates
two rules:
1) Feel free to close down a diaphragm, but only as much as you really need
to for the shot in question.
2) Larger formats will suffer much less, since the resolution needed in a
given format to product an acceptable print of a given size is lower.
This is a reason why so many "35 mm" lenses only stop down to f/16!
Enough for a Friday afternoon...
Don Feinberg
