Is my SL defective??

[Docderm]

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Just got this new camera as well as new Leica M to T and the Leica R to M adapters. 

Bizarre behavior: 

a) Attach a WATE via the Leica M to T adapter: set WATE to 21mm; Select the WATE lens profile for 21mm

Set the WATE to F4. 

c) Camera set to M mode

d) As I point the lens to different brightness areas of the room the displayed F stop is jumping to F8, to F16, to F9.5 while I have not changed the WATE F stop from F4

e) I have fixed ISO and fixed shutter speed. 

 

Same process using an R lens 60mm macro F2.8 via Leica R to M; then M to T adapter to camera body; selected the 60mm macro lens profile

Same bizarre behavior of the camera in M mode widely varying the displayed F stop (and the one recorded in EXIF) even though it is supposed to be in Manual mode where I have set F stop to 2.8 and have fixed iso and fixed shutter speed. 

 

What is wrong??

Is this a defective camera? 

 

Your thoughts are much appreciated. 

DocDerm

Edited July 4, 2016 by Docderm

[LD_50]

No aperture data is passed from lens to camera with M or R lenses. The sensor on the front of the camera guesses the aperture. 

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[Docderm]

Thank you for this very helpful clarification. 

 

If I understand right, just put the M or R lens on the aperture I want and take the picture. The recorded EXIF data will recognize the lens/allow you to choose it in the lens profile list BUT will not accurately record the actual F stop.....just the guessed f stop? 

[steppenw0lf]

Summary (R and M lenses): The camera will chose the right combination of the aperture that you selected and the time it chooses (in A mode).

The aperture which is displayed and some other data is not always completely right. But the picture is correct.

 

If you need precise data, buy the SL lenses. Then you are safe.

If you add other lenses, and you have never done that before, expect to find things you don't completely understand. 

Prepare to learn more about it. Maybe prepare to search the fault first in the user and not in the camera.  

 

If you don't like this - then use only the official lenses. SL 24-90 and SL 90-280 . Maybe also some lenses from the T camera.

[thighslapper]

Thank you for this very helpful clarification. 

 

If I understand right, just put the M or R lens on the aperture I want and take the picture. The recorded EXIF data will recognize the lens/allow you to choose it in the lens profile list BUT will not accurately record the actual F stop.....just the guessed f stop? 

 

The camera has a light sensor on the body at the front.

 

I compares the ambient light from there with the light on the sensor through the lens.

 

This comparison gives a (usually) reasonable guess of the lens aperture used. 

 

Partial covering of the sensor, oblique lighting and a host of other factors can confuse this system and lead to errors ..... but for most everyday use it gives as good an estimate as you will get with lenses with no electrical contacts to tell the camera what the aperture is. 

[LocalHero1953]

What you are seeing is the aperture the SL thinks you have used. In M mode, of course, it is not trying to set the aperture, just trying to guess a figure to go in the EXIF - this is often wrong by, say, a stop.

[Docderm]

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All these answers are very helpful in helping me understand how adapted Leica lenses act on the camra. 

Thanks!

[ramarren]

When fitted with an adapted lens for which it has a lens code, the SL displays the aperture based on an estimate that is a balance between what it has been informed is the lens maximum aperture, the amount of light coming through it and into the currently metered area on the main camera sensor, and the amount of ambient light it is reading through the external sensor at the upper-right of the body (looking at it from the front). It's always estimating the lens opening since it has no direct mechanical or electronic connection to any adapted lens' actual aperture setting ... that only works for dedicated lenses. 

 

How that external sensor reads is often thrown off based on how you're holding the camera and how your hand, and reflections of your skin, wiggle the readings. There's also lag associated with the display. 

 

So the basic rule of thumb: when using adapted lenses, ignore the aperture readout in the viewfinder or in the EXIF data afterwards. It is never better than an estimate. When using dedicated lenses, it will be accurate. 

[adan]

Addditionally, the external light-sensing eye has a fixed field of view. I don't know exactly what, but probably approximately a "normal lens" view of the scene (50mm).

 

Any time you use a lens that crops severely (90-135) or is extremely wide (i.e. 21mm), the internal and external sources are going to "see" vastly different views of the world, with different light and dark areas and light sources and such.

 

E.G. - you point your SL at a scene with an especially bright object/light near the center, using a 21mm lens. The external sensor "sees" mostly just the bright object. Your internal meter sees everything the 21 takes in, which may include a lot of darker background around the central object. Comparing the two "seen" brightnesses, the meter readout say "Boy, he must be using a really small aperture for the internal image to be that much darker," and estimates f/9.

 

The Leica digital rangefinders do the same thing. Usually, with a 75mm lens, the "guess" as to aperture is pretty close - f/2.7 when I actually used f/2.0, or similar. With a 135, it is always off, often recording "f/10" when I know I was using f/5.6.

 

Conversely, in the 21mm image below (MM), the external cell "saw" what is inside the circle, roughly. A dark car and street. The internal meter saw a lot of additional bright sky. Comparing the two brightnesses, the EXIF assumed I must have used a medium-wide aperture to get that much "brightness" from a dark car (f/6.7) - whereas I actually used f/11.

 

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Edited July 5, 2016 by adan