Hi everybody,
Startled by a recent mention of bodies unable to precisely set the
diaphragm aperture, I conducted a small test to see for myself. Not
that I care much as I set the aperture from the lens most of the
time, but I wanted to know how reliable exposure is for those rare
situations when I recourse to program or shutter speed priority.
Here's what I found: the MZ-5N consistently sets the aperture on
FA 28-70/4 half of stop higher across the entire range, from 4 to 19
(that is 4.5 instead of 4, ...22 instead of 19).
On the contrary, it is very accurate with the FA 50/1.4 and FA
80-320/4.5-5.6, where the size of the aperture set by the body
matches exactly the one set on the lens. So it seems it depends on
the lens, and not surprisingly in this case the poorer built lens
performed the worst.
If you're willing to test your lenses and report back on the list to
see if we can find a pattern, here is how to do it. Note that this
works only with bodies capable of electronic depth of field preview.
On the bright side, the error is easy to detect.
- set the aperture ring on the lens to A;
- set the aperture value on the body (with bodies like 5N lacking
this feature just set the shutter speed to some value, measure the
light and record the aperture selected by the body);
- press the DOF button to close the diaphragm;
- while keeping the DOF pressed, disengage the aperture ring from A
and rotate it towards the target aperture value while looking
through the lens at the size of the physical aperture; the blades
should maintain their position all the way down from A to and
including the target aperture; the true aperture set by the body
is the one before the aperture shape has changed.
Servus, Alin
