leica and the iso 100

[aral70]

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good morning I never write but I always read you!
I have a question for you:
I had a discussion with a friend regarding the iso of the leica M10 do you think the 100 iso are virtual or are they real?
let me explain better are they made through software or are they real?
Thank you

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[a.noctilux]

Welcome here Aral70.

Comparing sensor ISO to film which has ISO Standard (Wiki talk ) to sensor ISO (a reading) can be a benefit but in real life may not be useful.

 

More practical as user.

I use since 2017 M10, never use ISO 100 in real (only to try out once or twice), as I do understand that the 'real ISO' (from some discussions, really ?) of it's sensor is between 160-180

So 200 is fine for me.

 

have a read here for M10-R

 

more in this post

 

Edited August 21, 2021 by a.noctilux

[aral70]

thank you so much

[Casey Jefferson]

Probably to emulate the M9 dynamic range since people were complaining big time about M240 losing the Leica magic...

[farnz]

6 hours ago, Casey Jefferson said:

Probably to emulate the M9 dynamic range since people were complaining big time about M240 losing the Leica magic...

That was the M240's CMOS sensor versus the M9's CCD sensor rather than ISO grooming wasn't it? 

Pete.

[adan]

10 hours ago, aral70 said:

I had a discussion with a friend regarding the iso of the leica M10 do you think the 100 iso are virtual or are they real?

Image sensors all only have one "real" ISO, called the base ISO.

Which creates the optimal and most efficient sensor output - one photon in knocks loose one electron to be captured and counted, with no overflow. For the M10 24Mpixel color sensor, this is about "ISO 135-ish" according to Leica.

An analogy would be - put a needle on a rotating vinyl/wax sound recording, and the needle will vibrate and put out a given amount of sound all by itself. That is its "base volume." The original "phonographs" amplified the sound with a megaphone or trumpet - eventually electrical devices were used to amplify the vibrations (or "signal") instead.

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All the other ISOs a digital camera may offer come from processing the base ISO image with additional processing chips. Amplifying or "pushing" it to a higher ISO get a usable image using less light, or to a lesser extent subduing it with de-amplification ("pulling") to get a lower apparent ISO, a stronger signal and thus slightly less noise (better signal/noise ratio).

I guess those could be called "virtual ISOs." But I've never head that term used.

The ability to "pull" a digital image is very limited, since the base ISO is already using the full capacity of the sensor's "pixel wells" that store the electrons, and adding more light very quickly overflows the capacity of the wells to distinguish bright things, leading to "blown" highlights without detail.

On the basic M10, ISO 100 is a slight "pull" of the base ISO, and ISO 200 or higher are "pushes" of the base ISO (weaker and weaker native signals (sensor exposed to less light than optimal), amplified more and more, and thus acquiring more and more noise.) And for whatever reason (probably to maintain even steps: 100, 200, 400, etc., on the mechanical ISO knob), Leica does not allow accessing and using the actual base ISO.

...................

As to digital ISO compared to film ISO, the ISO (International Organization for Standards) standards for measuring each are completely different. Film ISOs are determined by measuring shadow density (although Ilford, for example, doesn't use the ISO method, for their own films). Digital ISOs are measured differently based on signal, noise, midtones - and only for .jpgs, since each photographer will do their own processing with raw of .DNG files).

Nevertheless, in practical use, they are generally close, so that an external independent light meter, which has no idea what camera one is using, should produce equally-bright pictures from the same light, subject, and manual camera settings.

The only way to really test that is a direct comparison with a color slide film of ISO 100 (no printing corrections allowed) and a digital .jpg taken at the same aperture and shutter speed at ISO 100 (no photographer post-processing - "straight from the camera").

The ISO organization doesn't come close to doing such a test, and I suspect most camera makers don't bother, either. DxO claims their testing system comes close, but it's still based on a "virtual" mathematical model, not shooting Velvia 100 alongside an M10 or the other cameras they test.

Scroll down halfway for digital ISO explanations and measuring techniques: https://en.wikipedia.org/wiki/Film_speed

Edited August 21, 2021 by adan

[jaapv]

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1 minute ago, adan said:

Nevertheless, in practical use, they are generally close

I have seen variations of +/- 1 EV. between different cameras.

[adan]

Of course. There is a reason I included the word "generally."

Edited August 21, 2021 by adan

[Casey Jefferson]

10 hours ago, farnz said:

That was the M240's CMOS sensor versus the M9's CCD sensor rather than ISO grooming wasn't it? 

Pete.

I've read quite some discussions where people were talking about how M10 were tweaked to look closer to M9. To get the similar dynamic range of the highlight, Leica didn't label ISO100 as "push" so people will use it.

Just my wild speculation. 😂

[a.noctilux]

Discussions can be useless if not to be practiced by oneself to add or not the feature to the palette.

So I invite the OP (and us all) to practice/try out then judge.

 

This ISO100 thing can be worked out very easily with every M10 ...

 

[farnz]

On 8/21/2021 at 12:11 PM, Casey Jefferson said:

Probably to emulate the M9 dynamic range since people were complaining big time about M240 losing the Leica magic...

 

7 hours ago, Casey Jefferson said:

I've read quite some discussions where people were talking about how M10 were tweaked to look closer to M9. To get the similar dynamic range of the highlight, Leica didn't label ISO100 as "push" so people will use it.

You first referred to the M240 so I refer you to p167 of the M240 manual, which says:

"The Pull 100 has the same brightness as a sensitivity of ISO 100. However, pictures taken using this setting have a lower contrast range."

The M10's manual doesn't mention pulled ISO but Andy Piper's post #6 mentions that Leica stated that the M10's Base ISO is 135-ish so the inference must be that ISO 100 on the M10 is actually pulled.  Is this an omission by Leica or simply that Leica views the real difference between ISO 135 and ISO 100 with the M10's sensor in terms of contrast and dynamic range are negligible and therefore not worth mentioning in the manual?  Only Leica knows.

Pete.

[adan]

4 hours ago, farnz said:

The M10's manual doesn't mention pulled ISO but Andy Piper's post #6 mentions that Leica stated that the M10's Base ISO is 135-ish so the inference must be that ISO 100 on the M10 is actually pulled.  Is this an omission by Leica or simply that Leica views the real difference between ISO 135 and ISO 100 with the M10's sensor in terms of contrast and dynamic range are negligible and therefore not worth mentioning in the manual?  Only Leica knows.

I think a clue here is that in the original M10 firmware, Auto-ISO could use ISO 100. In a soon-revised firmware, Auto-ISO was reprogrammed to never go below ISO 200.

Leica decided (very probably based on user feedback) that ISO 100 was  - different - and it was not a good idea to automatically drop people into ISO 100 without knowing it.

It actually was discussed at some length (with some shirtsleeve testing) as early as Jan/Feb. 2017.

Another clue is that the range of ISOs accessible by the ISO menu in the M10, generally spaced at 1/3rd-stop intervals (200, 250, 320, 400...etc) - also jump directly from 200 to 100. No 160, no 125. Like the M9, which jumped directly from ISO 160 (base) to ISO 80 (pull) with no intervening options.

Why it isn't mentioned in the Manual is unknown. Like Boeing and MCAS, Leica may have simply decided "Too much information that the pilots don't need to know - it'll just confuse them."

 

[Adam Bonn]

@adan

Hi Andy,

In that original (and excellently informative) thread you wrote this post

Quote

The ISO 200 picture is simply a slightly darker overall exposure, perfectly consistent with the differing exposure given (1/750 at ISO 200, but 1/350 (not 1/375) at ISO 100).

 

The highlights have more tonal detail, the shadows have less tonal detail (unless pulled up to a noisy level). The net range is about identical.

Obviously some years have passed since then and your opinion of the best usage of the camera may have changed

But between your and Jono’s writings on the subject I (quite possibly erroneously) took the whole ISO 100/200 thing not to be so black and white as always use 200 more specifically that in scenes where heavy shadow recovery in post was necessary (and the important highlights wouldn’t be clipped) then ISO100 was the best setting, whereas in very contrasty scenes with a mixture of dark and light, then ISO200 was recommended, sacrificing some shadow noise for highlight recovery

Is this still the best way of working with the M10 or is ISO 200 more of a better base for the vast majority of images?

Many thanks in advance

 

[M11 for me]

Another detail that might be of interest: Wen the M10 was launched with its first firmware then in Auto-Mode the ISO were set to ISO 100 as the lowest ISO. Soon after that in a Firmware update that value was changed to ISO 200 as lowest value. At that time in the forum there were already „tests“ published to show that there was more dynamics in the photographs at ISO 200 compared to ISO 100. In my setting I already started then to use ISO 200 as my basic setting.

[aral70]

thanks everyone for the answers I've been out of the house!

[aral70]

i couldn't thank you before!