A question about the MATE, coding and focal length recognition.

[Robert Campbell]

I was organising, and came across some images taken with the MATE. It was a coded lens, and this was correctly recognised.

But...in a series of three images I noticed that the focal length is recorded in the EXIF as 28mm, 35mm and 50mm. Looking at the pix, this is clearly correct.

How is this focal length recognition possible? There is only one code on the lens itself.

 

[Bernard]

Robert,

It probably uses the position of the frame mask cam.

 

[jonoslack]

Robert,

It probably uses the position of the frame mask cam.

Bernard has it - which is why it doesn't work with the WATE (which doesn't change the mask).

best

 

[Robert Campbell]

Bernard has it - which is why it doesn't work with the WATE (which doesn't change the mask).

best

Thanks. That makes sense.

But...why doesn't this work for uncoded lenses? If the camera can recognise a change of focal length from the frameline selector, why not for all that do change the framelines? Or is the potential confusion between 28/90, 35/135 and 50/75 just too much?

 

[scott kirkpatrick]

There are actually 8 bits in the lens code. Six from the little painted spots, and two more to represent the three positions of the frame line lever. Since the MATE actually moves the lug in the mount which pushes on some internal levers connected to the frame lines, the camera can see this. The M8 firmware had tables in which this could be seen. The extra two bits are used as a check on identifying a lens. If the frame line position is wrong, the lens may not be recognized even if it is coded.

scott