Originally posted by Argenticien I agree with tromboads that typically the SR setting provides the focal length. But it would still be nice to know the aperture setting, so your idea is still interesting. I don't know anything about creating electronics, but just as a common-sense observation, I should think this would be very difficult for one simple reason: There is seemingly nowhere to put such a chip. Since the M42-to-Kmount adapter is just a tiny ring, and M42 has same film-to-flange distance as K, there is almost no space for electronics or contacts. It's in adapters with considerable front-to-back length, like from any film SLR mount to mirrorless, that you could have space for chips, contacts, and even an aperture. But maybe some hacker out there will prove my assumption wrong!
SR is great, but (i dunno about newer body) on the K-x it doesn't allow to enter
any value, but only preselected value (28, 35, 40, 50, 55, etc ...).
About the chip : i'm currently repairing a Sigma 28-70/ 2,8-4
Sigma 28-70mm F2.8-4 UC Lens Reviews - Sigma Lenses - Pentax Lens Review Database, the data info don't work currently because the wiring between the mount and the circuit board is cut. I'm re-wiring it and re-brazing.
The chip part is really small, and there is plenty of room between the glass and the barrel to stock everything. In fact, the biggest part is about the AF elements to tell the body the distance marking of the focusing group, when focusing (the body pre-determine where the foccus group should go, it moves, then the body re-check if the focusing is good, and can re-ask to move the focusing group accordingly).
On the picture, the biggest part of the circuitry is used for the AF system.
Hence, if anyone could decode the communication passing trough the data pin (look there to understand
Features and Operation of the Kaf Mount ), i could probably make a diagram for the chip.
The chip required to communicate just a focal lenght, min and max aperture, and the name / provider of the lens, is really chip. I cost less than 1 bucks ! i think with all the wiring it can be done for 3 to 5 bucks.
All i need is an electronic engineer to can decode the communication
Any volonteer ?
Last edited by aurele; 01-20-2014 at 10:40 AM.