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Auto ISO and minimum shutter speed


mirekti

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I am not sure why the following was not implemented in the latest FW, or I don't know how to enable it.

 

Let's say I put the camera in an A mode, and choose to use Auto ISO with the following parameters:

 

Max ISO:1600

Max Exposure Time: 1/125 s

 

In case I come in a situation where to obtain the correct exposure camera needs 1/60s. Why does the camera slower the shutter speed? I'd rather have an underexposed image, and work on it later than a blurry one. I understand I could set the shutter directly on 1/125s. Setting it to 1/125s is not the point as the light changes quite quickly, and I need for example for camera to go to 1/2000 as well.

 

I guess there is one missing option in the Max Exposure Time, and that would be Disabled which would work as now, where all other option would mean that they are "Maximum Exposure Time"

 

I mean, isn't the whole point of Max Exposure Time not to get a blurry image in the first place? :confused:

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As usual the maximum exposure time does not specify an absolute maximum; rather it informs automatic exposure which exposure times it should try to avoid by increasing ISO. Once the ISO value has reached its own limit (as set by the user), automatic exposure will do what it is programmed to do in aperture prority mode: it will adjust the shutter speed as required for an optimum exposure.

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Your confusion with this is perfectly understandable. When I first used the camera in low light, I was confused as well, as have many other newcomers to the Leica digital world.

 

The thing is, despite what the menu system may imply, you cannot set a minimum shutter speed when shutter speed is set to Auto. This is a misconception that Leica has caused by poor naming of that function with little to no explanation in the manual.

 

The name of the menu setting (minimum shutter speed in auto exposure) would lead most normal people to conclude exactly what you have. What they should have done was give this function a better name, something like Auto ISO Threshold or something. And then clearly explained in the manual what it does.

 

As others have said, in order to achieve a minimum shutter speed, you must set the camera to manual shutter speed. Once you are aware of this, it isn't really a problem.

But there is no way to simultaneously have an automatically controlled shutter speed as well as a guarantee of a minimum shutter speed. It's not possible with the M camera.

 

In my opinion a professional camera should be flexible enough to offer people that functionality if they really prefer to have it that way. Leica could easily do that by having another menu state that turns on or off a hard minimum shutter speed in auto shutter speed mode. This wouldn't complicate things too much, as long as it was properly explained in the manual.

 

But as others have said, the workaround is simply to use manual exposure and let the indicators in the viewfinder guide you to the correct exposure. Also, with the latest firmware, you can enable Auto ISO in manual shutter speed mode which works very well too.

 

I am not sure why the following was not implemented in the latest FW, or I don't know how to enable it.

 

Let's say I put the camera in an A mode, and choose to use Auto ISO with the following parameters:

 

Max ISO:1600

Max Exposure Time: 1/125 s

 

In case I come in a situation where to obtain the correct exposure camera needs 1/60s. Why does the camera slower the shutter speed? I'd rather have an underexposed image, and work on it later than a blurry one. I understand I could set the shutter directly on 1/125s. Setting it to 1/125s is not the point as the light changes quite quickly, and I need for example for camera to go to 1/2000 as well.

 

I guess there is one missing option in the Max Exposure Time, and that would be Disabled which would work as now, where all other option would mean that they are "Maximum Exposure Time"

 

I mean, isn't the whole point of Max Exposure Time not to get a blurry image in the first place? :confused:

Edited by paulsydaus
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...In case I come in a situation where to obtain the correct exposure camera needs 1/60s. Why does the camera slower the shutter speed?...

Because it is not clever enough to know that you prefer under exposition to motion blur. Just set the shutter speed dial to 1/60s and the camera will obey you.

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I wonder whether there is any camera behaving differently? That is, is there a camera where you can limit the shutter speeds chosen in aperture priority mode? Auto ISO settings generally only concern Auto ISO; they don’t affect automatic exposure, except indirectly since the chosen shutter speed also depends on ISO.

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I wonder whether there is any camera behaving differently? That is, is there a camera where you can limit the shutter speeds chosen in aperture priority mode? Auto ISO settings generally only concern Auto ISO; they don’t affect automatic exposure, except indirectly since the chosen shutter speed also depends on ISO.

 

My Nikon D4 offers more modes of operation than I will ever need and it does not offer this feature. Don't think I would want it to. I prefer the various modes to be discrete. When they start to overlap I think it can create confusion. That was my issue with the M Typ 240 initial Auto ISO implementation. In my view changing the shutter speed dial should have no effect on one's Auto ISO settings.

 

Regarding Auto ISO in Aperture Priority mode. I have not experienced this with my digital Ms, but with my Nikons I occasionally experience some rather bazaar exposures when letting the camera's meter adjust shutter speed and ISO simultaneously. I get more consistent results when I allow the camera to automatically adjust only one exposure factor.

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