Lens Detection - What Does It Do?

[Dennis]

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An example, so I can understand better, it's not my expertise branch 🙂 Let's think about this scenario. One has a ZM 35/2.8, a CV 35/1.2III, a Leica 50/2, and a CV 21/3.5, all mounted on an M10 with lens detection set to OFF. So, what does actually happen?
I mean, no full EXIF, maybe vignette and purple fringing, Italian flag, etc ... But my question is, for the 35 and 50, perhaps I don't get any of these issues, right? But for the 21, all of them?
For better practice, I like the idea of setting lens detection ON (if 6-bit coded) or OFF and forget the problem, EXIF, etc. I don't need perfection, just speed.

If one has many lenses that need different lens profiles, how is it possible to save them in the user menu? We can't. Four user profiles, I guess, is the limit.

[Jeff S]

As noted, purple fringing is not addressed by 6-bit coding.

Jeff

[Herr Barnack]

For the record, purple fringing is addressed by the $8795 USD APO-Summicron-M 50mm f/2 ASPH lens (as well as Leica's other APOs).  😄

Edited February 23, 2021 by Herr Barnack

[jaapv]

3 hours ago, Herr Barnack said:

I would like to jump in here with a couple of questions.

I read the FAQ about 6 bit coding but there was no mention of correcting for purple fringing.

It seems that purple fringing is a separate issue/problem apart from color shift in wide lenses - is that the case?

How is purple fringing corrected?

 

In general purple fringing is longitudinal chromatic aberration as expressed on a sensor. It can easily be corrected by a slider in Lightroom.

[Herr Barnack]

4 minutes ago, jaapv said:

In general purple fringing is longitudinal chromatic aberration as expressed on a sensor. It can easily be corrected by a slider in Lightroom.

In Lightroom, under Lens Corrections (right sidebar), I see a box that can be checked named "Remove Chromatic Aberration."

I'm not finding a slider that is similarly named, though.

[UliWer]

vor 2 Stunden schrieb Dennis:

If one has many lenses that need different lens profiles, how is it possible to save them in the user menu? We can't. Four user profiles, I guess, is the limit.

Besides the information for the EXIF lens detection mainly reduces vignetting. The „Italian flag syndrom“ (magenta and green shadows in the corners) is increased by the lenses vignetting, i.e. the loss of light the lens lets through to the sensor. Reducing vignetting may help against the green and magenta as well. Though in my experience the „italian flag syndrom“ is no big issue anymore for the M10, certainly less so than for earlier M models.

 So if your lens is not in the menu you might choose one which has the same focal length and perhaps a similar amount of vignetting. In some cases the reduction of vignetting is too strong, than you better choose another lens in the menu or switch it off. Of course you have to choose your indiviual settings manually - which one often forgets with changing a lens. Though if you use a coded lens afterwards the M10 will only use this code, not the one you have choosen manually.

If you use Auto-Iso and/or flash, lens detection may be helpful as well, as you can define your settings according to the focal length. 

Edited February 23, 2021 by UliWer

[Jeff S]

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52 minutes ago, Herr Barnack said:

For the record, purple fringing is addressed by the $8795 USD APO-Summicron-M 50mm f/2 ASPH lens (as well as Leica's other APOs).  😄

Partially.  Read the link from adan (Andy) that I provided.

Jeff

[Dennis]

19 minutes ago, UliWer said:

Besides the information for the EXIF lens detection mainly reduces vignetting. The „Italian flag syndrom“ (magenta and green shadows in the corners) is increased by the lenses vignetting, i.e. the loss of light the lens lets through to the sensor. Reducing vignetting may help against the green and magenta as well. Though in my experience the „italian flag syndrom“ is no big issue anymore for the M10, certainly less so than for earlier M models.

 So if your lens is not in the menu you might choose one which has the same focal length and perhaps a similar amount of vignetting. In some cases the reduction of vignetting is too strong, than you better choose another lens in the menu or switch it off. Of course you have to choose your indiviual settings manually - which one often forgets with changing a lens. Though if you use a coded lens afterwards the M10 will only use this code, not the one you have choosen manually.

If you use Auto-Iso and/or flash, lens detection may be helpful as well, as you can define your settings according to the focal length. 

Thank you.

So, if my lens are all Zeiss, or Voigtlander, and I have a preferred/specific lens to associate with in the user profile, how is the best practice for an M10? For me best practice, is being more practical: less menu clicks and more speed. My point is how beautiful auto is 🙂 But with many no Leica lenses, do I have a choice? I would love to avoid to enter in the menu every time I change a lens. But because I can't do that, at least I can have a user profile for each lens I use. Four profile saved in not enough.

[Jeff S]

54 minutes ago, Herr Barnack said:

In Lightroom, under Lens Corrections (right sidebar), I see a box that can be checked named "Remove Chromatic Aberration."

I'm not finding a slider that is similarly named, though.

Jeff

[jaapv]

1 hour ago, Herr Barnack said:

In Lightroom, under Lens Corrections (right sidebar), I see a box that can be checked named "Remove Chromatic Aberration."

I'm not finding a slider that is similarly named, though.

 

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[Tailwagger]

On 2/19/2021 at 6:30 PM, lct said:

Depends on the camera. On M cameras, it corrects mainly for color shift issues (aka "red edge" on some WA lenses) and mentions the name of the lens in the exif data.

Perhaps worth mentioning that one other crucial (to the camera, perhaps not to the individual photographer) thing lens detection/manual specification achieves now is enabling perspective control as the calculations depend, similar to IBIS, on knowing the focal length. 

[lct]

3 hours ago, Tailwagger said:

Perhaps worth mentioning that one other crucial (to the camera, perhaps not to the individual photographer) thing lens detection/manual specification achieves now is enabling perspective control as the calculations depend, similar to IBIS, on knowing the focal length. 

Thank you for this info about M10 cameras i guess. The OP asked about the M246 though. Not sure if perspective control works for that camera as well. It does not on my M240 at least. 

[blackdot]

3 hours ago, Tailwagger said:

Perhaps worth mentioning that one other crucial (to the camera, perhaps not to the individual photographer) thing lens detection/manual specification achieves now is enabling perspective control as the calculations depend, similar to IBIS, on knowing the focal length. 

 

3 minutes ago, lct said:

Thank you for this info about M10 cameras i guess. The OP asked about the M246 though. Not sure if perspective control works for that camera as well. It does not on my M240 at least. 

I think the pc thing is only for M10 variants and not the original M10 or earlier cameras. 

[Tailwagger]

26 minutes ago, lct said:

Thank you for this info about M10 cameras i guess. The OP asked about the M246 though. Not sure if perspective control works for that camera as well. It does not on my M240 at least. 

Indeed, just backfilling in terms of general info. The original M10's lack the level gyro, so they are definitely out, but the 240 (246 as well?) had it, so it's presumably possible from a  technical perspective.  Of course the likelihood of a firmware update for this is at best remote.