Question about Perspective control

[lct]

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I need some help about Perspective control.
While it works normally with lens detection auto, it is disabled on my M11 when lens detection is off.
The same with coded or uncoded lenses.
I guess it is normal as the camera needs to know the focal length of the lens.
But i read so many statements that lens detection is always on that i wonder if i'm missing something.
Not that i believe all i read on the web but could someone confirm or correct?
Thank you in advance 🙂

[gweber]

„The focal length of the camera lens must be known to use this function. It is automatically detected when M lenses with 6-bit encoding are used. The lens type must be entered manually when other lenses are used (Lens Detection).“ Source: https://www.reddotforum.com/content/2021/01/leica-perspective-control-for-m10-r-m10-p-and-m10m/

Similar reference in the handbook.

 

Cheers,

Gernot

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[lct]

Thank you @gweber but the focal length is not automatically detected when lens detection is set to off. I guess it is normal but the "lens-detection-always-on" theory doesn't seem to work here.

[hmzimelka]

1 hour ago, lct said:

Thank you @gweber but the focal length is not automatically detected when lens detection is set to off. I guess it is normal but the "lens-detection-always-on" theory doesn't seem to work here.

As @gweber wrote; If there is no 6-bit coding "The lens type must be entered manually when other lenses are used (Lens Detection)"

I don't follow your logic for "lens-detection-always-on  theory doesn't seem to work here"  How so? If there is no 6-bit code how can the camera detect what lens is attached???? 

Edited March 6 by hmzimelka

[hmzimelka]

Let me make this a little easier for you to understand with a video showing how lens-detection is always on.

Starts off with a Summicron 5cm Collapsible on my camera with a manually selected Summicron 50 profile selected. 
I change this to Lens Detection off. 
I switch the camera off and on and show that lens detection is still off, since the camera cannot detect a 6-bit coded lens!
I then switch lenses and mount a 6-bit coded Summicron-M 50mm V while the camera is on. 
As you can then see on the rear LCD, the lens selection AUTOMATICALLY goes from "OFF" to 2/50 (Summicron 50mm) after it has detected the lens!

https://flic.kr/p/2pBQ6fn

 

Edited March 6 by hmzimelka

[lct]

53 minutes ago, hmzimelka said:

[...] I don't follow your logic for "lens-detection-always-on  theory doesn't seem to work here"  How so? [...]

If this theory would work, lens detection could not be set to off when a coded lens is used but fact is it can, or am i missing something?

[hmzimelka]

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4 minutes ago, lct said:

If this theory would work, lens detection could not be set to off when a coded lens is used but fact is it can, or am i missing something?

have you looked at the video I posted? 

It's not a theory.

I don't know why it is the way it is. If it were up to me, lens detection OFF would mean OFF, always and forever until set otherwise. But it's Leica, who knows what they are thinking!

[lct]

I think i told you so already but i'm not good at theories or hypotheses sorry. I'm just interested in facts and fact is that lens detection can be set to off when not only uncoded but also coded lenses are used. It's Leica indeed and it' a good idea as there are circumstances when i want lens detection to be off.  I do like this freedom that works perfectly for me. YMMV.

[hmzimelka]

Wow! Look at the video! 
I went through the effort to make a video for you to show how it works and you still think it's a theory? Did you even watch it?

I give up!

[01af]

vor 4 Stunden schrieb lct:

... but the focal length is not automatically detected when lens detection is set to off. I guess it is normal but the "lens-detection-always-on" theory doesn't seem to work here.

Ummm ... which part of 'lens detection is set to off' don't you understand? Off means off. When it's set to off then it's not on, and when it's on then it's not off. Because 'off' is the opposite to 'on.' So switch the lens detection mode to off, and it will be off, even when a 6-bit-coded lens is mounted.

But then, when the camera awakes from stand-by or gets switched off and then on again, it will take a fresh look at the 6-bit code. If it finds one then it will read and accept it, no matter what was selected in the lens detection menu before. And this behaviour makes sense—it saves the user from erroneously applying the wrong lens identification after switching from an uncoded lens to a 6-bit-coded one. It used to be a common user error to forget to switch back lens detection to 'auto' after changing from an uncoded lens to a coded one.

Edited March 6 by 01af

[lct]

33 minutes ago, 01af said:

So switch the lens detection mode to off, and it will be off, even when a 6-bit-coded lens is mounted.

Exactly what i said below.

2 hours ago, lct said:

fact is that lens detection can be set to off when not only uncoded but also coded lenses are used.

 

[01af]

vor 3 Minuten schrieb lct:

Exactly what I said below.

Yes, you did, and correctly so.

But the confusion obviously comes from the fact that lens detection won't stay off when the camera gets re-started and a 6-bit-coded lens is mounted.

[marchyman]

1 hour ago, hmzimelka said:

I give up!

You are talking apples and oranges.

Apples: lens detection will switch from off to on if a coded lens is present when the camera is switched on.

Oranges: lens detection will be off when turned off even if a coded lens is attached -- until the next time you cycle power

Those are two different things.   Let me add a third which I'm going to test right now

• Put a coded lens on my M11 and take a picture.
• Turn lens detection off and take a second picture.
• Wait for the camera to go to sleep.  Will lens detection still be off when it wakes up?
• Wake the camera up with a half press of the shutter and take a third picture
• Check lens detection.

Surprise, surprise. Lens detection turned back on when the camera woke up.  This is what was recorded in the metadata for the three images:

First picture: Apo-Summicron-M 1:2/75 ASPH .
Second picture: no lens info
Third picture: Apo-Summicron-M 1:2/75 ASPH .

In short, you can turn off lens detection and it will stay off until the camera sleeps or is turned off.   When the camera is turned on or awakened from sleep lens detection reverts to auto if a coded lens is mounted.