Come to think of it, I'm not at all sure that the method on Z-1 shows what we want it to.
When the lens is _not_ mounted on the camera, the aperture coupler (handle) is in a resting position determined by a spring in the lens. If turned to "A" position, the aperture blades will rest at the smallest available f-stop, eg. f/22. When the lens is mounted, the aperture is forced to open because the handle is pressed down by a lever in the camera. During exposure, this lever lifts up allowing the handle to move exactly enough to rest at the correct aperture (in theory, at least). With pre-selected aperture, the _lens_ decide completely which position the aperture should rest at during exposure. With the "A" setting, the _lever_ in the camera decides. You may have had this sorted out already, but I had to go through that reasoning for my own sake... :-) Now, the _real_ question behind this is: how the heck can the camera know the exact position of any one particular f/stop? I think this has been discussed here on the list before, but it's got to be at least two or three years ago, and I can't recall the conclusion... Jostein ----- Original Message ----- From: "Alan Chan" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, March 12, 2003 9:43 AM Subject: Re: Re[4]: Diaphragm actuator precision survey > >The Sigma 70-200/2.8 is supposedly well built but still displays > >the error. Too bad we cannot draw a lens-related conclusion. It > >appears the mechanism itself requires very low tolerances both on > >the camera and the lens and is very prone to error. :o( > > Definitely. I don't think it has to do with the built quality of the lenses. > Perhaps the cost would be too high if they had to make the end products > close to absolute accuracy. These are the results that I have found with my > Z-1p. > > Right on: > A35/2.8, A50/1.7, 70-210/4 > > Appears right on except not fully opened at wide open: > FA77/1.8 > > Less than 1/2 stops larger than it should be: > FA*24/2, FA43/1.9, F*300/4.5, FA*200/2.8 > > 1/2 stops larger than it should be: > FA100/2.8 > > regards, > Alan Chan > > _________________________________________________________________ > Add photos to your e-mail with MSN 8. Get 2 months FREE*. > http://join.msn.com/?page=features/featuredemail > >
