> When choosing the 20-35, it was helpful to do some optical
> calculations. So I made a Javascript lens calculator
> intended eventually for eosdoc. The current draft is at:
> http://members.home.net/jul.loke/
Julian
where *all* these calculations really break down (especially when
trying to prove finer points) is that the manufacturers "economy with
the truth" hides from you the data you really need to know. But it is
for your own benefit: auto-everything cameras do it all for you, no?
What is the focal length?
What is the aperture?
What is pupillary magnification (at each alleged focal length and
aperture)?
What is inter-nodal distance (at each focal length and aperture)?
If you always hand-hold why worry about ultimate sharpness?
The fact is the numbers reported by the lens-camera are, if not
"lies", are often falsehoods. Whilst getting anal with optical
formulae is great fun (seriously) I always hold back some scepticism
when the numbers we feed it are not that precise anyway.
Oh, I use Microsoft Excel for Optical Calculations. Can't beat it for
flexibility ...
BobT
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