Recently Hugo Kok wrote:
>
> another question to check out the Pentax Data Base that is YOU.
> Situation is: comparing three of my lenses with fixed aperture (let's
> say: 5.6), the light meter gives on all three of them a different
> exposure time. That is: 50mm OK, 85mm +1 stop, 135mm +1/2 stop. After
> extensive comparisons in which all possible other explanations were
> ruled out, it left me with the only remaining cause: the 'pen' inside
> the mount of the lens that mechanically tells the camera what aperture
> is momentarily in use is not in proper place in two of the lenses.
No, no, no. Two possibilites are: non-uniform subject, that is, you have
different portions of the image with the different lenses or the light
changes a bit while you change lenses. Another one is that the aperture
blades are not 100% corectly positioned. in other words, the aperture
setting 5,6 is in reality 7,1 or something like that.
> Now here's my question: is it possible to open up the rear of the lens
> myself, adjust the relative position of the 'pen' a little and at the
> same time be reasonably confident to end up with a working lens?
It is possible to open the lens but there is no possibility to adjust the
position of the lever. The only adjustment is to the positions of the
blades, but these are calibrated and then the adjustment screws are fixed
with paint or glue. All in all, not an advisable operation.
The only thing that I think you can do is inspect that lever for dirt or
damage, and this only externally, without disassembling the lens.
Cheers,
Boz
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