leica cl CL, Auto-ISO algorithm/ bias

[danielfrimley]

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Has anyone used Auto-ISO enough to note whether the CL exhibits a stock preference to either shutter speed or ISO speed, or is it so damn smart it automagically knows which you would wish to be quicker?

For example, when moving from indoor to strong sunlight and back again, setting at ISO max 6400, with a shutter minimum of 1/60s in AP mode you might expect sharp images with manageable noise all the time, but is it truly pot luck shot to shot which variable the camera changes to correct exposure?

Is it true to say the function produces consistent results with only a "short range" set, if so what have you found to be acceptable?

Three question marks in one post, sorry about that.

[wda]

Cannot explain your suspicions. However, for your scenario I would resort to manual mode for precise and predictable control. In fact it is a classic example where two user profiles, one for indoors and one for outside, are so helpful.

[ramarren]

My experience is that the CL camera simply follows its program line when in AutoISO, regardless of indoor/outdoor/etc. When the minimum shutter speed setting is reached, it starts to raise the ISO setting until it hits that limit. 

Unlike some other cameras which have an "automatic extended" range on the time factor when the high ISO limit is reached, Leica's implementation of AutoISO simply allows the image to be underexposed when the high ISO and shutter time limits are reached, and overexposed when the low ISO and minimum shutter time limits are reached. It indicates this when you check exposure with a half-press of the shutter release. 

Note that my experience with the behaviors of the CL exposure system are limited to its behaviors when used in M and A modes only, since I do not own or use any L mount lenses. There may be other nuances to the exposure system's behavior in P and S modes with native L mount lenses. 

[M11 for me]

What do you call MINIMUM SHUTTER SPEED OF 1/60th. Do you mean maximum? Or longest which allows besides the 1/60th as well 1/125, 1/500th etc.

What sense would it make to define 1/60th as shortest and allow 1/30, 1/15th etc.?

I might misunderstand something here.

Edited April 2, 2019 by M10 for me

[ramarren]

The terms "minimum shutter speed" and 'maximum shutter speed" are often used interchangeably and ambiguously. The more precise way of stating what is meant is "minimum exposure time" and "maximum exposure time". I participate occasionally in this ambiguity, my apologies. 

Rewriting what I wrote above: 

"Unlike some other cameras which have an "automatic extended" range on the time factor when the high ISO limit is reached, Leica's implementation of AutoISO simply allows the image to be underexposed when the high ISO and maximum exposure time limits are reached, and overexposed when the low ISO and minimum exposure time (as short a time as the shutter selector or electronic shutter will allow) limits are reached. It indicates the limits have been reached when you check exposure with a half-press of the shutter release."

The notion of an "automatic extended" mode is simple: there are many occasions, mostly at the low light end of the spectrum, where the right exposure for whatever reason ends up being a short fraction of a second longer than the set limit. If your shooting situation is happening on this boundary frequently in a given session, AutoISO on the Leica CL and SL becomes somewhat unusable and it doesn't have to be: That small extension to shutter speed is often well within the capability of a good photographer to handle occasionally. What enabling this mode on cameras equipped with it usually does is present a warning (usually flashing or changing the color of the exposure time readout) that you've moved into an over-ride situation so that you don't keep blasting away without being aware of it but automatically do the extension so that you don't lose a "one time only" potential shot. 

It took me a while to understand that Leica did not provide the kind of automatic override and warning that other cameras I used had. It still seems something of an omission to me. There are times when the rigor of having a hard limit beyond which the camera will not go is a good thing ... they should complete it and just enable locking the shutter release in those situations so that you're well and truly prevented from making a bad exposure. But most of the time I just would like a warning that I've hit the set limit and the exposure time will run a bit longer if I proceed. 

It's a philosophical difference, that's all. I've become accustomed to how the Leica AutoISO notions work now, and usually switch my camera to a fixed ISO when it's going to be working in a condition were the boundaries are stressed frequently. It slows things down a little because there are times when I really want the ISO to automatically jump up a stop or two, but eh? I make do.

 

[danielfrimley]

15 hours ago, M10 for me said:

What do you call MINIMUM SHUTTER SPEED OF 1/60th. Do you mean maximum? Or longest which allows besides the 1/60th as well 1/125, 1/500th etc.

What sense would it make to define 1/60th as shortest and allow 1/30, 1/15th etc.?

I might misunderstand something here.

Of course you're right. I mean 1/60s set as the longest exposure time that the camera will allow in a changing light scenario. Minimum as slowest, not minimum as interval.

[lct]

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A minimum speed is a minimum speed. What is confusing is the use of "maximum exposure time" by Leica. Both mean exactly the same so better use the easiest to understand IMHO. BTW Leica uses "minimum shutter speed" for its PanaLeica and T cameras IINW but i have no experience with them. 

[dau]

5 minutes ago, lct said:

A minimum speed is a minimum speed. What is confusing is the use of "maximum exposure time" by Leica. Both mean exactly the same so better use the easiest to understand IMHO.

Exposure time is exactly what it says: the duration of the exposure. It usually is measured in fractions of a second. It's the magnitude which is engraved on practically all cameras on the speed dial. Hence, 1/20 means one twentieth of a second, and 1 means one second. The larger number stands for the longer exposure.

Speed, on the other hand, is defined as a distance divided by an amount of time, such as 3 miles/1 second or 25 km/h. Longer times mean slower speeds. Actually, the term "speed" is a misnomer when applied to the exposure dial as it does not imply any distance at all. Otherwise, the same exposure duration would be expressed by a larger speed for a larger image format.

In this vein, I think "exposure time" and "maximum exposure time" are easier to understand and consistent with the speed dial, and "speed" and "minimum speed" can lead to confusion, particularly when larger speeds are expressed by smaller numbers.

[lct]

I beg to differ. Everybody understands what shutter speed means. Leica used this term widely in its analogue manuals and still use it nowadays. For example, to explain that « shutter speeds can easily be changed » thanks to the shutter speed dial of the M5, that « opening up the diaphragm by two stops corrects the exposure value for purely white details. i.e. multiplying the shutter speed by 4 » (Leica M6), or that the M8 can takes a second black picture « with slower shutter speeds » than 1/30s. Or that « for shutter speeds slower than 2s, the message Noise reduction in progress » appears in the M9 monitor. Or that auto iso « varies ISO sensitivity for correct exposure when shutter speed and aperture are set manually » (M240). Or to explain that « higher sensitivities allow faster shutter speeds and/or smaller apertures for "freezing" rapid movements » (digital CL). Or that « the S2 is equipped with a metal focal-plane shutter with the fastest shutter speed of 1/4000 of a second » (Leica S2),  et cetera, and so on, und so weiter.
Why doing simple when you can do complicated .

[jaapv]

The point is that exposure time is not the same as shutter speed. The speed of the shutter is invariable, but the exposure time varies with the width between the blades.

[ramarren]

3 minutes ago, jaapv said:

The point is that exposure time is not the same as shutter speed. The speed of the shutter is invariable, but the exposure time varies with the width between the blades.

I'm glad someone understands. Presuming a focal plane shutter, of course... 

[papimuzo]

And a pure mechanical shutter😋

[Guest]

On 4/3/2019 at 3:53 AM, ramarren said:

The terms "minimum shutter speed" and 'maximum shutter speed" are often used interchangeably and ambiguously. The more precise way of stating what is meant is "minimum exposure time" and "maximum exposure time". I participate occasionally in this ambiguity, my apologies. 

Rewriting what I wrote above: 

"Unlike some other cameras which have an "automatic extended" range on the time factor when the high ISO limit is reached, Leica's implementation of AutoISO simply allows the image to be underexposed when the high ISO and maximum exposure time limits are reached, and overexposed when the low ISO and minimum exposure time (as short a time as the shutter selector or electronic shutter will allow) limits are reached. It indicates the limits have been reached when you check exposure with a half-press of the shutter release."

The notion of an "automatic extended" mode is simple: there are many occasions, mostly at the low light end of the spectrum, where the right exposure for whatever reason ends up being a short fraction of a second longer than the set limit. If your shooting situation is happening on this boundary frequently in a given session, AutoISO on the Leica CL and SL becomes somewhat unusable and it doesn't have to be: That small extension to shutter speed is often well within the capability of a good photographer to handle occasionally. What enabling this mode on cameras equipped with it usually does is present a warning (usually flashing or changing the color of the exposure time readout) that you've moved into an over-ride situation so that you don't keep blasting away without being aware of it but automatically do the extension so that you don't lose a "one time only" potential shot. 

It took me a while to understand that Leica did not provide the kind of automatic override and warning that other cameras I used had. It still seems something of an omission to me. There are times when the rigor of having a hard limit beyond which the camera will not go is a good thing ... they should complete it and just enable locking the shutter release in those situations so that you're well and truly prevented from making a bad exposure. But most of the time I just would like a warning that I've hit the set limit and the exposure time will run a bit longer if I proceed. 

It's a philosophical difference, that's all. I've become accustomed to how the Leica AutoISO notions work now, and usually switch my camera to a fixed ISO when it's going to be working in a condition were the boundaries are stressed frequently. It slows things down a little because there are times when I really want the ISO to automatically jump up a stop or two, but eh? I make do.

 

 

Its not “Leica’s interpretation”.....it’s the way it’s implemented on the CL/SL. 

On my M10 in auto-ISO,  the exposure time will increase beyond the auto-ISO setting

Edited April 3, 2019 by Guest

[ramarren]

1 hour ago, hemlock said:

Its not “Leica’s interpretation”.....it’s the way it’s implemented on the CL/SL. 

On my M10 in auto-ISO,  the exposure time will increase beyond the auto-ISO setting

The implementation in firmware is Leica's interpretation. LOL!

Besides: We're talking about the CL here, not the M line cameras. The firmware in Leica's CL is more closely related to the firmware in the X, Q, and SL series cameras than the M. The M cameras do many things somewhat differently ... obviously, a different development team did the work on them. 

[lenspeeper]

After reading the previous posts, I wondered if my own interpretation is incorrect. So, just for clarification, when the Leica CL menu says Minimum Shutter Speed , It is referring to the slowest  shutter speed you want to set when defining the range of Auto ISO range. Are we on the same page or did I frail to understand?

[wda]

1 hour ago, lenspeeper said:

After reading the previous posts, I wondered if my own interpretation is incorrect. So, just for clarification, when the Leica CL menu says Minimum Shutter Speed , It is referring to the slowest  shutter speed you want to set when defining the range of Auto ISO range. Are we on the same page or did I frail to understand?

That is my interpretation too. It becomes clear when you delve into the choices given to the photographer in the sub-menu. 

[lenspeeper]

9 hours ago, wda said:

That is my interpretation too. It becomes clear when you delve into the choices given to the photographer in the sub-menu. 

Thanks.