>
> Surely with the 100mm USM Macro + 1.4 extender + 36mm extension
tube, wide
> open is only about f11 anyway at 1:1 ?
> Does this give a correct aperture read-out on the camera, as I
thought that
> adding any two accessories stopped this working.
>
> Cheers
>
> Keith
Careful not to confuse "aperture" and "effective aperture".
If you put an f2.8 lens on bellows and extend the bellows: the
aperture remains f2.8.
The effective aperture (reflecting the amount of light getting though
to the film plane: defined for exposure calculations) may not be:
what it is is far from simple to calculate except for theoretical
lenses.
An f2.8 lens on a 1.4 extender ... well, that sort of is f4 (subject
to caveats)
An f2.8 lens on a 36mm tube then a 1.4x extender ... never have
managed to get even the experts to quote on that ;o)
For macro you really need to consider just the magnification and the
aperture. Pragmatically, you just need to know what aperture the
camera reports for OK shots.
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