Aperture metadata not matching lens setting

[jwillyf]

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I have a Type 246 and have noticed that the aperture metadata is not matching that on the lens. Generally the metadata is recording aperture as 1 stop higher than the lens setting. For example f4 on the lens is recorded as f4.8 on the metadata, and f11 as f13.

In the menu, lens recognition is set to automatic.

This is on a coded Summicron 50 mm f2 serial no 2331077.

I was thinking of DIY coding a Voigtlander Ultron 35 mm f1.7 and an Elmarit 90 mm f2.8.

Any ideas on the discrepancies on the Summicron.

Thanks

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[tom.w.bn]

The camera is guessing the aperture. No electronical contacts between aperture ring, bajonett and camera. The camera can't know exactly what aperture is set.

[jwillyf]

Thanks for the reply.

Are you saying that the Summicron I have is not capable of supplying the EXIF data because it cannot connect electrically?

Edited December 24, 2020 by jwillyf

[tom.w.bn]

vor 7 Minuten schrieb jwillyf:

Thanks for the reply.

Are you saying that the Summicron I have is not capable of supplying the EXIF data?

No Leica M lens on the planet is capable of delivering aperture information. The 6-bit code only helps to identify the lens.

[jwillyf]

Thanks for that. It was the significance of the coding on the lens that was confusing me. An elementary error, I guess, but another item of information gleaned on my Leica journey, a journey started quite late in life! Thank you for your input.

Edited December 24, 2020 by jwillyf

[pippy]

Just to put a little bit more flesh on the bones;

The small circular 'window' at the shutter-speed-dial end of the front edge of the top-plate allows an approximate measure of the available light reading to be taken and it is this, coupled with the shutter speed, which provides the roughly-calculated aperture setting you see subsequently in the data panel.

As far as I understand it the lens code has two functions only; one to provide the EXIF information (as regards lens used) and secondly to allow for in-camera lens correction so that some unwanted (perhaps) aspects of a lens' inherent rendering - vignetting for example - can be dialled-out at the shooting stage.

Philip.

Edited December 24, 2020 by pippy

[jwillyf]

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Interesting, Philip.

So if an M lens is coded, should I set Lens Recognition in the menu to Automatic so that the lens used is reported in EXIF, or is the camera not able to recognise the lens anyway, because there is no electrical contact?

Edited December 24, 2020 by jwillyf

[pippy]

38 minutes ago, jwillyf said:

...So if an M lens is coded, should I set Lens Recognition in the menu to Automatic so that the lens used is reported in EXIF, or is the camera not able to recognise the lens anyway, because there is no electrical contact?

Yes; the function of the coding is to allow for EXIF data and in-camera lens correction. The 6-bit code IS recognised by the camera - there is an elongated 'wndow' on the lens-mount on the body at the 5 o'clock position which reads the code - but this only tells the camera which lens is attached; nothing more.

The reason that no exact aperture data can be recorded is because there is no 'information' connection between the lens' aperture ring and the camera body - either physical or electrical - and so there is no way that the setting can be known by the camera.

With the majority of recent non-coded lenses the model of lens can usually be selected in the appropriate drop-down menu if the option is set to Manual instead of Auto. For even older non-listed lenses then choosing the closest possible match (in terms of focal length and max aperture) can also be useful.

Philip.

Edited December 24, 2020 by pippy

[pedaes]

30 minutes ago, jwillyf said:

should I set Lens Recognition in the menu to Automatic

I think if you mount a coded lens the camera defaults to lens recognition. Try it.

[pippy]

2 minutes ago, pedaes said:

I think if you mount a coded lens the camera defaults to lens recognition. Try it.

Ah! My Monochrom is the M9 version so perhaps the auto-thing came later on with the 246 such as owned by the OP.

My only newer-than-M9 experience is with the M-D Typ-262 and, for obvious reasons, this feature isn't wholly relevant!

Philip.

[pedaes]

3 minutes ago, pippy said:

on with the 246

In truth, I can't remember what my Typ.240 did, which is the 'try it' bit. The M10 defaults, but this might be the first software to do this.

Have a good Christmas!

[jwillyf]

With lens recognition set to automatic, all three lenses in my OP reported 'lens not selected'.

[pedaes]

3 hours ago, jwillyf said:

With lens recognition set to automatic, all three lenses in my OP reported 'lens not selected'.

Sorry to send you down a blind alley!

[tom.w.bn]

vor 4 Stunden schrieb pedaes:

I think if you mount a coded lens the camera defaults to lens recognition. Try it.

Don't have the 246. With the M240 it's either automatic or manual. When I set a lens manually, the lens code is completely ignored.

[tom.w.bn]

The sensor at the lens mount that detects the 6-bit code is sensitive to dirt. If it's not clean, lens recognition does not work. After I change a lens, I press the Info-Button and check in the display if the correct lens is diplayed.

 

[jwillyf]

Cleaned the 6 bit code sensor and set Lens Recognition to manual. Just have to remember to dial in the lens every time I change lenses.

Thanks all.

[Gobert]

Screw a strong ND filter on the lens and you will see the camera is confused about the aperture. 
In my opinion this means that the 6 bit code has no direct function in recognising aperture.

[jaapv]

The camera determines the aperture by reading out the external light meter (the little "eye" on the front of the camera) and comparing the value with the measured EV to arrive at an estimated value. The 6-bit coding has obviously nothing to do with it as it does not change with the aperture setting. It will tell the camera the maximum aperture of the lens, of course, but not the actual setting.

Setting the lens recognition to manual only makes sense if you mount an uncoded lens with a mount screw in an unfortunate position over the reader. Otherwise it is useless - unless the recognition fails technically.  In general, if you mount an uncoded lens, the camera will switch to manual setting of its own accord.

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Hallo,

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[jwillyf]

12 hours ago, jaapv said:

Otherwise it is useless - unless the recognition fails technically.  In general, if you mount an uncoded lens, the camera will switch to manual setting of its own accord.

Thanks. That’s helpful.