Re: istD test

[Robert Gonzalez]

But what feedback does the body have to set the aperture to the correct 
setting?  I think he was talking about setting it to the "A" setting, in 
this case the highest aperture, then letting the body do the rest.  If 
the body is depending on a linear movement on the linkage, then its 
going to move the lever the wrong amount.  The steps are much bigger for 
wider apertures on an M lens than the smaller apertures.  On an A lens, 
they are all equally spaced, so its easy to set a particular aperture, 
or interpolate between them.

Mark Roberts wrote:
Robert Gonzalez <[EMAIL PROTECTED]> wrote:


You actually need a spring loaded contact to short out the recessed pin 
on the body.  Then you still wouldn't get the correct exposure.  Non-A 
lenses do not have a linear aperture engagement lever, so the body would 
dial the wrong aperture when stopping down.


I think you *would* get the correct exposure, if you could install the
spring-loaded contact as described: If I understand the mechanism
correctly, the geometric, rather than linear, movement of the aperture
engagement lever, it would cause it to move *more* than is required to
stop down to the selected aperture, not less.