6-bit coding and Auto Lens Detection

[lct]

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34 minutes ago, jaapv said:

[...] The coding has nil impact on the functioning of the framelines.

My understanding too, but when changing the focal length, does it appear automatically in the camera and/on exif data? Just curious again.

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[jaapv]

Never tested it but it would be surprising if it didn’t. 

[lct]

Just tested my uncoded MATE. In manual detection mode, coding it as such, the lens is detected as "Tri-Elmar-M 1:4/28-35-50 ASPH. @ 28mm" at the 3 focal lengths and the 3 positions of the frame selector. Framelines are of no apparent effect on the detected focal length, as expected. Same in manual detection mode as "Tri-Elmar-M 1:4/28-35-50 ASPH. @ 35mm", changing the focal length or the position of the frame selector is of no effect. Same again in manual detection mode as "Tri-Elmar-M 1:4/28-35-50 ASPH. @ 50mm", changing the focal length or the position of the frame selector is again of no effect. I can't figure out how it could be different in auto lens detection mode, but i'm no techie.

Edited Monday at 11:14 AM by lct

[lct]

Again tested my uncoded MATE, this time pen coded as such (101010). The position of the frame selector doesn't change anything apparently but the lens is recognized in auto detection mode and focal lengths do change in both camera display and exif data depending on the setting of the lens. There is no conflict between 6bit code and framelines this way, which pretty well answers my question.

[misteracng]

11 hours ago, lct said:

Just tested my uncoded MATE. In manual detection mode, coding it as such, the lens is detected as "Tri-Elmar-M 1:4/28-35-50 ASPH. @ 28mm" at the 3 focal lengths and the 3 positions of the frame selector. Framelines are of no apparent effect on the detected focal length, as expected. Same in manual detection mode as "Tri-Elmar-M 1:4/28-35-50 ASPH. @ 35mm", changing the focal length or the position of the frame selector is of no effect. Same again in manual detection mode as "Tri-Elmar-M 1:4/28-35-50 ASPH. @ 50mm", changing the focal length or the position of the frame selector is again of no effect. I can't figure out how it could be different in auto lens detection mode, but i'm no techie.

This is the same behavior as I have seen. On the M11 with the coded MATE, it changes the focal length only when physically changing the focal length on the lens, as this adjust the frameline stop mechanically telling the camera which focal length you are using. Moving the frameline selector doesn't change anything. So only in auto mode does it select for you as you change the lens focal length. It seems if you manually select the MATE, the camera will not change the focal length, maybe because it assumes you want that specific lens profile. There is no other way to test this because mounting a coded mate is auto detected, the manual lens selection is disabled.

[DadDadDaddyo]

This is also my impression of the behavior. The coding tells the body it's a MATE, and then the lens tells frame selector what focal length it's at. 

[lct]

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Unsure what the frame selector does in this matter. Its positions have no effect on lens detection, be it in manual or auto mode, anyway.

[DadDadDaddyo]

As I understand it, there are two mechanical inputs to the frame selector mechanism. 

The lever on the front of the camera permits you to change the frame selection, manually and temporarily, to preview the field of view of lenses, as a kind of assistance in deciding which lens to select for a shot.

Internally, the frame selection for the viewfinder is determined by the cutout on the flange of the lens: when you attach the lens, that mechanical coupling engages and puts the correct frame into place in the viewfinder. 

The legendary mechanical complexity of the MATE is demonstrated, in part, by the fact that it changes the position of the frame selection cutout on its flange as you select the focal length. 

Lens detection, as governed by the 6 bit coding, simply tells the camera the name of the lens, its identity. Thus, the camera body does a lookup (in ROM, I presume) and retrieves basic data about the lens, its focal length and maximum aperture, for example, and whether and what vignette correction to apply. 

The 6 bit coding has no role in viewfinder frame selection, which is determined mechanically by the cutout of the rear flange of the lens. 

Edited yesterday at 01:24 PM by DadDadDaddyo

[misteracng]

3 hours ago, DadDadDaddyo said:

As I understand it, there are two mechanical inputs to the frame selector mechanism. 

The lever on the front of the camera permits you to change the frame selection, manually and temporarily, to preview the field of view of lenses, as a kind of assistance in deciding which lens to select for a shot.

Internally, the frame selection for the viewfinder is determined by the cutout on the flange of the lens: when you attach the lens, that mechanical coupling engages and puts the correct frame into place in the viewfinder. 

The legendary mechanical complexity of the MATE is demonstrated, in part, by the fact that it changes the position of the frame selection cutout on its flange as you select the focal length. 

Lens detection, as governed by the 6 bit coding, simply tells the camera the name of the lens, its identity. Thus, the camera body does a lookup (in ROM, I presume) and retrieves basic data about the lens, its focal length and maximum aperture, for example, and whether and what vignette correction to apply. 

The 6 bit coding has no role in viewfinder frame selection, which is determined mechanically by the cutout of the rear flange of the lens. 

Agreed, the flange is different for each frameline, that position is being sensed which gives more 6 bit possibilities and also what allows auto focal length detection, it’s the only lens that can change the flange anyways. The frame like selector lever is u related. It allows changing the frameline but the flange is what picks the correct default frameline e

[jdlaing]

5 hours ago, DadDadDaddyo said:

As I understand it, there are two mechanical inputs to the frame selector mechanism. 

The lever on the front of the camera permits you to change the frame selection, manually and temporarily, to preview the field of view of lenses, as a kind of assistance in deciding which lens to select for a shot.

Internally, the frame selection for the viewfinder is determined by the cutout on the flange of the lens: when you attach the lens, that mechanical coupling engages and puts the correct frame into place in the viewfinder. 

The legendary mechanical complexity of the MATE is demonstrated, in part, by the fact that it changes the position of the frame selection cutout on its flange as you select the focal length. 

Lens detection, as governed by the 6 bit coding, simply tells the camera the name of the lens, its identity. Thus, the camera body does a lookup (in ROM, I presume) and retrieves basic data about the lens, its focal length and maximum aperture, for example, and whether and what vignette correction to apply. 

The 6 bit coding has no role in viewfinder frame selection, which is determined mechanically by the cutout of the rear flange of the lens. 

Not by the cutout but by a lug.

[DadDadDaddyo]

I assumed it was that scooped-out shaped cutout. Thanks!

[jaapv]

On 10/7/2025 at 3:15 AM, lct said:

Unsure what the frame selector does in this matter. Its positions have no effect on lens detection, be it in manual or auto mode, anyway.

That is incorrect as some lenses will revert to uncoded if the frame selector lever is moved out of position. 

[IkarusJohn]

@lct 45 posts to @jaapv’s 38 - who’s going to win?

[jaapv]

Reality I hope. 

[lct]

2 hours ago, jaapv said:

That is incorrect as some lenses will revert to uncoded if the frame selector lever is moved out of position. 

It doesn't work this way with the MATE, on my M11 at least. Whatever its position, the frame selector has no effect on lens detection. I have no experience with your M9 though. Do you have other lenses at mind?

[LocalHero1953]

I just checked in to this thread to see why it was always showing in my New Content activity stream.

I wish I hadn't.