Hi,
What surprises me is that the magnification ratios of these two lenses are
almost the same (0.14 for the 20mm vs 0.13 for the 20-35) while their
closest focusing distances are quite different.
How can that be?
Pierre
At 19:19 2/25/2001 +0000, you wrote:
> > Magnification on the 20mm is 0.14 and it's 0.13 on the 20-35... How
>can
> > this be with such a difference in closest focusing distance.
>
>
>The close-focus is a function of focal length AND inherent bellows
>extension.
>Why is actually a very interesting question. I'm wondering if it is
>akin to the *so-called" doublers. They don't actually double the
>focal length they just magnify the centre of the image circle giving
>an image on film the size that would ....
>
>Thinking aloud ... maybe the reason the 20-35 can't be made to focus
>as close as the 20 is that the latter is a 20mm and the second a 35mm
>front end being made to behave as a 20 by jiggery-pokery. Were that
>true the minimum focussing distance would certainly be limited by
>physics not design ....
>
>I'm intrigued to know if anyone has hard facts on this.
>
>Bob
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