David Jenkinson <jenkinson@xxxxxxxxxxxxxxxxxxxxxx> moved upon the face of the
'Net and spake thusly:
> But, and here's the rub.....as one of the answers pointed out,*all* zoom
> lenses, by definition *should* be variable aperture, shouldn't they? After
Look into the front of any zoom lens as you zoom it.
If you can see the aperture diaphragm, you will see it appear to grow
larger as you zoom the lens (as it must do, to maintain the same
relative aperture at different focal lengths).
This can happen because the element arrangement changes in complex
ways as you zoom.
With a constant (maximum) aperture zoom, the size of the aperture
keeps getting bigger as you zoom all the way to maximum focal length.
With a variable (maximum) aperture zoom, a point is reached where the
lens can no longer maintain maximum aperture, and starts to drop off.
Its just a matter of how complicated the movement of the lens elements
is (and how wide the lens is overall).
--cjb
--
It's boring being a program when your only job is inserting a random .sig.
Muggins thinks I've put his .sig here, won't he be surprised...
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