Default base ISO on Q3 vs M11

[setuporg]

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Although the sensor is the same, the M11 got the vaunted 64 while the Q3 is still the uncle’s 100.  Why?

[Elliot Harper]

I always thought M11 base ISO is somewhere around 160.

[Robert Ardinger]

I wonder if there is a difference due to the need for the sensor "system" (micro lenses, downstream processing, etc.) on the M11 to be able to handle a variety of lenses and the sensor "system" in the Q3 perhaps being able to be "adjusted" for it's one and only lens.  

The Photons to Photos (P2P) web site graphs for Dynamic Range (DR) versus ISO has the sensor of the Q3 having peak DR at ISO 100 (as does the SL3 graph) but the M11 data suggests it's best DR is at ISO 64 which correlates with the listed Base ISO of 100 for the Q3 and 64 for the M11 (Leica lists a lower "base" ISO of the SL3 as 50 but 100 seems like a more realistic value and is the base ISO the camera apparently uses when in Auto ISO ).  Other than that the DR graphs are pretty equivalent (there is a "dual gain" type bump at 200 for the M11 and 300 for the SL3 but no significant one for the Q3).  

The P2P graph for DR Shadow Improvement seems to suggest that the M11 and SL3 sensors act fairly similarly but the Q3's sensor has quite a different graph and apparently better DR shadow improvement.

The similarities in the M11 date to the SL3 data (both interchangeable lens cameras) and their differences with the Q3 (fixed lens) data are what made me wonder about the Q3 sensor being optimized for it's (only) lens and might explain why there are different specifications for the "same" sensor when placed in different cameras.

I claim no real in depth knowledge of how all this works and not at all sure (at least for me) that it makes much difference for the final results on actual images but learning about digital sensor function is (sort of) fun and at least as interesting as learning about Hurter and Driffield (H&D) sensitometry ("S") curves nearly half a lifetime ago when I was "Zone Systeming" my way through film exposure and developing.

[SrMi]

13 hours ago, setuporg said:

Although the sensor is the same, the M11 got the vaunted 64 while the Q3 is still the uncle’s 100.  Why?

The sensor toppings and the hardware and firmware around it are different.

[SrMi]

12 hours ago, Elliot Harper said:

I always thought M11 base ISO is somewhere around 160.

Base ISO for M11 is 64.

[setuporg]

On 4/30/2025 at 9:29 AM, SrMi said:

The sensor toppings and the hardware and firmware around it are different.

So this is really interesting — the low ISO of 64 was celebrated in the M forum as return to classic film, while in the Q/SL one nobody cares.  Which may or may not mean it’s also a style, not quality, issue.

[SrMi]

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3 hours ago, setuporg said:

So this is really interesting — the low ISO of 64 was celebrated in the M forum as return to classic film, while in the Q/SL one nobody cares.  Which may or may not mean it’s also a style, not quality, issue.

I am unsure why ISO 64 should be related to classic film. Instead, it helps shooting Noctilux lenses wide open in bright daylight. It also provides 2/3 more PDR at ISO 64 than SL3 at ISO 100.

Edited May 1 by SrMi

[Leslie22]

The love of ISO 64 , may relate to the film days of Kodak 64 ??

[FlashGordonPhotography]

4 hours ago, SrMi said:

I am unsure why ISO 64 should be related to classic film. Instead, it helps shooting Noctilux lenses wide open in bright daylight. It also provides 2/3 more PDR at ISO 64 than SL3 at ISO 100.

I have found zero real world differences in DR between the M11 and SL3. I defy anyone to see a usable difference between ISO64 on the M11 and 100 on the SL3. It's nothing more than a chart measurement and has nothing to do with reqal world shooting/processing.

And since the mechanical shutter of the M11 tops out at 1/4000 vs 1/8000 on the SL3 there's no benifit there either.

There are three variants of the 61MP Sony sensor. The M11 one doesn't have PDAF pixels. As well as the other things you mentioned.

Gordon

[SrMi]

1 hour ago, FlashGordonPhotography said:

I have found zero real world differences in DR between the M11 and SL3. I defy anyone to see a usable difference between ISO64 on the M11 and 100 on the SL3.

ISO 64 means that one can have one stop larger exposure. This is the noise difference between SL3 at ISO 100, lifted five stops in LrC, and M11 at ISO 64, lifted four stops, and with one stop larger exposure. Now, whether that is a realistic test is debatable, but the effect can be observed. A one-stop difference matters more at higher than at lower ISOs.

 

 

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[FlashGordonPhotography]

1 hour ago, SrMi said:

ISO 64 means that one can have one stop larger exposure. This is the noise difference between SL3 at ISO 100, lifted five stops in LrC, and M11 at ISO 64, lifted four stops, and with one stop larger exposure. Now, whether that is a realistic test is debatable, but the effect can be observed. A one-stop difference matters more at higher than at lower ISOs.

 

 

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So (assuming invariance) you're comparing an SL3 at 3200 and an M11 at ISO1250 in tha above image?

Gordon

[SrMi]

15 minutes ago, FlashGordonPhotography said:

So (assuming invariance) you're comparing an SL3 at 3200 and an M11 at ISO1250 in tha above image?

Gordon

One stop difference in exposure, so 3200 vs 1600. With ISO 64 we can have approx. one stop larger exposure than with ISO 100, one stop better shadows.

Edited May 2 by SrMi

[Miltz]

Shooting below 100 ISO on the Q3 isn’t recommended. Highlights get clipped.