[Medex]

Would this allow you to select focus points, like an AF lens as well?

Interesting project!

I did not try at yet selection, because I rarely use this focusing mode, but I think, the answer will be YES.

---------- Post added 10-30-18 at 09:17 AM ----------

Hacking the ROM data is not going to be easy. As said before it can easily brick the chip. How did you read the ROM data anyway? You have a flashrom programmer?

You said you can set the focal distance the chip reports to the camera? How is that done?

I use the same method as UncleVanya uses for SDM to screw drive conversion.
The focal distance can be set mechanically by soldering some contacts going out ot of the chip. There are 5 contacts. Different combinations allow to get different focal distances

---------- Post added 10-30-18 at 09:19 AM ----------

Are you sure maximum aperture/aperture range is transmitted by the data pin with the chip you are using?* Default is to use the mount contact pattern, even on AF lenses. This can be tested by masking the data pin and seeing what maximum aperture is detected.


Steve

* The camera body determines available apertures by calculation from minimum aperture and aperture range as encoded by the mount contacts or provided by polling the data contact.

I blocked the 7th "digital" pin and then the camera allows to select max aperture f1,2. But Face detection does not work in this situation.

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Last edited by Medex; 10-30-2018 at 12:20 AM.

[K1N8]

The focal distance can be set mechanically by soldering some contacts going out of of the chip. There are 5 contacts. Different combinations allow to get different focal distances

If this is already a feature of the chip, then setting Aperture via a similar method might be very very likely. Do you have "names" or ID's of the chip? Finding some schematics of the circuit might help. Or specifications, manuals, code, etc.


Also, 5 contacts would allow more combinations then needed for setting just focal distance. Maybe a combination also sets focal distance AND aperture.

[stevebrot]

Also, 5 contacts would allow more combinations then needed for setting just focal distance. Maybe a combination also sets focal distance AND aperture.

All but one of the contacts are legacy KA. Those are purely passive with binary state and are typically hard-wired and not controlled by the "chip".* They provide lens type ("A" vs. "non-A") and supported aperture settings. The two either side of the "A" contact encode the minimum aperture and the others (data contact excepted) encode the available number of aperture settings in half-stop increments. Maximum aperture is not explicitly encoded.

The contact pattern on the OP's mount is typical for an auto-focus K-mount lens. Note that the contact-encoded aperture information may be overriden by a poll for dynamic state through the data contact. This feature provides easy support for variable maximum aperture zooms.

Note: It is a small matter, but important to note that the contacts provide lens state information and are not used for lens control.


Steve

* There are some non-AF designs where the contact state is managed by a simple logic device, but it is easiest to simply consider the array to be hard-wired.

[K1N8]

Note that the contact-encoded aperture information may be overriden by a poll for dynamic state through the data contact.

Very interesting.


OP did speak of 5 contacts coming out from the chip, that are used for focal distance settings. Not the contacts on the mount between lens and body!?

The focal distance can be set mechanically by soldering some contacts going out ot of the chip. There are 5 contacts. Different combinations allow to get different focal distances

Also

I blocked the 7th "digital" pin and then the camera allows to select max aperture f1,2.

but with the data pin OP gets f4.5, so it is possible the chip overrides it to f4.5

If i understand OP correctly this isn't a "normal" lens chip anyway.

[stevebrot]

OP did speak of 5 contacts coming out from the chip, that are used for focal distance settings. Not the contacts on the mount between lens and body!?

Thanks for the clarification. I remember reading that, but did not put the two together.


Steve

[K1N8]

I blocked the 7th "digital" pin and then the camera allows to select max aperture f1,2. But Face detection does not work in this situation.

Please look at Decoding of the Lens Information Contacts and try changing the reported aperture from the lens to the body, by blocking/unblocking one of the F-stop range pins (1,5,6). Keep the data pin intact.


This might solve your problem without changing the ROM file, unless the lens chip overrides the aperture on the data channel.

[Medex]

Please look at Decoding of the Lens Information Contacts and try changing the reported aperture from the lens to the body, by blocking/unblocking one of the F-stop range pins (1,5,6). Keep the data pin intact.


This might solve your problem without changing the ROM file, unless the lens chip overrides the aperture on the data channel.

OK, I tried different variants of blocking one or several contacts. Everytime I lost automatic identification of focal lenght from the chip and Face detection functionality. Then I blocked "A" pin (3rd). The face detection function works, there is no aperture displayed, but HSS on flash does not work. So, I decided to leave everything as is, i.e. f4,5 aperture. This setting affects just EXIF data but not affects Face detection or HSS flash mode.
BTW, I did experimens with ROM file data from unafected same type lens I used as a donor to get the chip and PK bayonet with contacts. ROM data are changing every time when the focal lenght or aperture is changed to different values. It means that aperture value is controlled from the chip, but it is not clear the aperture value could be set to less than f4.5 (i.e. 1,8 for example).
Tkank for collaboration, guys