The lens aperture stop down lever could be bent not making proper contact with the in camera lever. That's the only thing I can think of.
Vic Mortelmans wrote: > OK, so I fixed the major problem, but it seems that I still have the > other problem that I detected when examining the first. In A-mode, the > lens diaphragma is a bit smaller (about one stop, I guess) then what the > camera says. > > No big deal, but I'd like to understand what's going on. This looks more > like a mechanical problem that won't be solved by CLA? Any ideas? > > How does the A-mode work? I imagine it's like this: > > - inside the camera body, I see a litter lever that engages the > diaphragma control lever on the lens. > > - when in M-mode, the lever in the camera body just moves all the way up > (releases the diaphragma to close, but the lens mechanics will stop it > at the f-stop selected on the lens); after exposure, the lever in the > camera body moves down again, and pulls the lens diaphgragma open > > - when in A-mode, the lens allows the diapragma to be operated > completely by the lever, so it's the camera that controls how far the > lever is moved upwards, and thus how much the diaphragma is allowed to > close. > > Reasoning like this, I'd rather expect the cause of the problem to lie > within the camera... Can anyone second that? > > Groeten, > Vic > > Vic Mortelmans schreef: > >> Hi, >> >> this was easy!! >> >> I went to a shop that does camera maintenance, and they estimated 75 >> euro for the job --- more than the lens is worth. So I was lucky: a good >> reason to take a look at the inside of the lens without the risk of >> destroying value. >> >> There was nothing wrong with the blades (as I expected, because oil on >> the blades should be visible, shouldn't it?), but there was oil in the >> mechanism. See the picture here: >> >> http://picasaweb.google.be/vicmortelmans/Tech/photo#5076727091233563442 >> >> It shows the back of the lens with the mount removed (only five screws >> and one loose ring, no tiny bits jumping allover the room). The red line >> indicates the two sliding parts that had oil inbetween them. Applied >> some aceton and now the diaphragma closes as snappy as it can get. >> >> Groeten, >> >> Vic >> >> >> Vic Mortelmans schreef: >> >>> Hi Mat, >>> >>> You're right. The blades are not 'snapping' together when releasing >>> the switch. I compared to my SMC M 28 f:2.8, which behaves a lot more >>> 'snappy'. >>> >>> I never sent a lens out for CLA... what would be a reasonable price >>> for this job? Any chance of trying this myself? >>> >>> Groeten, >>> >>> Vic >>> >>> >>> Mat Maessen schreef: >>> >>>> On 6/15/07, Vic Mortelmans <[EMAIL PROTECTED]> wrote: >>>> >>>>> The shots on part 2 are all overexposed... >>>>> >>>>> I don't use program mode that often (mostly aperture priority), so >>>>> could >>>>> it be that this mode is malfunctioning? The diaphragma control by the >>>>> camera is certainly doing something; I did a quick test in shutter >>>>> priority mode and saw the diaphragma change when selecting different >>>>> shutter speeds. >>>>> >>>> Most probably, your A50/2 need a CLA. The diaphragm blades are most >>>> likely not closing down quickly enough. You can test this manually, >>>> by looking through the back of the lens, and toggling the aperture >>>> lever manually with your finger. The aperture blades should snap >>>> closed when you release the lever, and you shouldn't feel any >>>> stiffness or resistance in the lever motion (set the lens to f22 or A >>>> for this test). >>>> >>>> -Mat >>>> >>>> > > -- All dogs have four legs; my cat has four legs. Therefore, my cat is a dog. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
