Re: Pentax Daddy-D: better compatibility with K and M lenses (was something else)

[Steve Jolly]

You could just have a single "calibrate" button.  Point the camera with 
lens attached at a scene that isn't going to change much during the 
half-second or so it takes to calibrate the lens*, and the camera scans 
through a hundred or so possible aperture-coupler positions and records 
the position that's closest to each half-stop.  Having a method of 
storing the settings for each of the lenses in your collection would be 
the icing on the cake.  It's perfectly feasible - the mechanical problem 
is certainly no harder than positioning the heads on a hard disk.  You'd 
have to tell the user to close the aperture to its narrowest limit 
before calibrating, but other than that, I think that the method gives 
the camera all the information it needs.  Including, I think, the lens 
information required to enable matrix-metering. :-D

Now, whether Pentax would ever consider investing the R&D money required 
to produce such a camera, given that it could only have a negative 
impact on their lens sales, is another question entirely... ;-)

S

*or just sell a range of lens-caps with built-in calibration 
light-sources...

John Mustarde wrote:

If the Daddy-D comes with full aperture coupling, driven by a stepper
motor or some such, Pentax could build a settings function, whereby
the camera remembers the aperture lever positioning requirements for
any particular lens.  This would calibrate each lens one by one to
compensate for any difference in linearity of its aperture mechanism.
The setting function would be primarily for K and M lenses, but could
be used for any lens operated in manual aperture mode.
The operator would  input settings for each lens, perhaps based on
in-camera histogram level tests made with the exact lens to be used,
limited perhaps to even f-stops for simplicity. Plus the operator
would choose that setting each time the lens in question was mounted.
But it is possible to do this, if driving the aperture actuation lever
position can be computerized and individualized.  It's also likely
very usable if the setting was one-button and you just had to quickly
press through the two or twelve K lenses you own to get to the one you
were about to mount.
So you attach your M20/f4, assign it a name within the camera computer
(like "M20/4"), take exposures at each aperture click stop, calibrate
a curve using the histogram for each f-stop, check exposure, loop back
if needed until the exposures are spot-on at each aperture, save the
setting, then do the same for the old Vivitar Series 1 90-180/4.5 Flat
Field Macro Zoom ("Viv90-180"), followed by the M200/2.5, etc until
every K or M lens in your bag had its name and calibration in memory.
This is a simple calibration sequence like those used in industry
every day.
Switching the lenses around would require selecting the name of the
lens from a menu or better yet a single-purpose button.  Sounds very
feasible, and very much a value add proposition for the Daddy-D to me.
I'd pay and extra fifty bucks for this feature.


--
John Mustarde
www.photolin.com