On Gio, 15 gen 1998 17:59, Shawn Wright <mailto:swright@xxxxxxxxx> wrote:
>It would seem that this was somewhat more than 1:1 magnification, but I
don't
>remember which lenses combined to give this result.
Easy: we can calculate the diopters (that is 1000/focal lenght) of each
lens and then sum up the two values and then again find the resulting focal
lenght.
FI:
(every couple of lenses of the same lenght turns out as the half of their
focal lenght)
100mm + 50mm = 10d + 20d = 30d = 33mm
50mm + 28mm = 20d + 36d = 56d = 18mm
Since the added lenses are a kind of additional lenses, no exposure
correction is needed (but you are in macro work, of course).
The optical center (centre) should result pulled ahead from the single
lens, but I think the diaphragm required to use is the mounted lens' one
only.
Marco
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