No correct exif data when using R-M adapter

[doc steel]

Does anyone know the problem that the largest aperture is not properly reproduced or transmitted when using the R-M adapter on the M240 ?

Specifically: With the Apo Telyt 3.4/180 I took a series of fixed-time exposures with different apertures in 1/2-stop increments, just as the aperture ring locks into place.
The corresponding lens profile is correctly selected in the camera.
If you look at the individual images and call up the Exif data, then you will read:
Exp. 1 which was taken with f3.4 shows always f4,
Exp. 2 taken with f4 shows f4,
Exp. 3 taken with f4.8 shows f4.8,
Exp. 4 taken with f5.6 shows f5.6 etc.

I have the same problem when using the Elmarit 2.8/90.
f2.8 and f3.5 will be displayed as f4 and from f4 on everything will be ok again.

Basically, and on the whole, I do not care, just stupid if you want to look and there are wrong values.
And I would like to know anyway if I am not alone with this matter.

 

[Mackinaw]

The EXIF readout I get when I use my LTM Canon 50/1.4 on my M240 is often off by one stop. I shoot at F2.0 and it reads F2.8. So you’re not alone.

Jim B.

 

[Godfrey]

The f/number reported in the EXIF data with a Leica M camera is always an estimate based on the selected lens profile, the ambient light sensor, and the actual exposure made. This is because there is NO direct connection between the aperture setting of any lens and the camera body.

The estimate is almost always off by some amount, to the point that the later firmware revisions now do not write the taking aperture to the EXIF data at all. Better no data than (very frequently) incorrect data...

G

 

[Doug]

While the 6-bit coding lets the camera know the identity of the lens mounted, there is no other mechanical or electrical way for the camera to know the aperture you've set. But it can estimate it... There is a light sensor in the small round window near the red Leica logo on the front of the camera. In cooperation with the TTL metering, this can give a calculated estimate of the relative aperture used. A bit odd I think that for you the estimate is consistently wrong at full aperture.

 

[Bike Tourist]

My M262 with latest firmware DOES still estimate the aperture. It's usually within 1/3 f-stop.

 

[Gregm61]

Same here with my M262. What seems to be the most often "missed" actual settings, F8 is often reported as f6.8 and f2 often shows up as f2.4, and all of my lenses are 6 bit coded.

If inaccurate aperture settings in the EXIF data drives one crazy, the M system isn't the best system to be using, LOL...