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Re: Leica M11 Monochrome Dynamic Range

ISO is a representation of apparent brightness, it is not a setting of the sensor.

As you can see the sixth gain setting has a DR jump on both cameras as the sensor switches to its other gain mode.

There is no such thing as increased signal due to gain setting. If a sensor records more photons at base iso (compared to another at base iso) it has a higher quantum efficiency and thus higher signal to noise ratio if the noise produced by both sensors is identical. If the noise introduced by equivalent gain is less then the snr is likewise higher. ISO 125 on the M11M is the exact same gain setting on the IMX455 as ISO 64 on the M11.

At ISO3200 (for example) both cameras will produce an image of similar brightness, but the M11M is effectively using a lower gain mode due to higher quantum efficiency from removal of the CFA.

The reason the exact same gain setting on the M11M produces less DR than on the M11 is because of minor benefits to noise introduced by Bayer interpolation.

The reason the M11 surpasses the M11M at ISO200-320 is because of the coincidental overlap of the best SNR of second gain mode on the M11 with the worst of the first gain mode on the M11M. This is pretty clear on the graph.

zhangyue wrote:
Remove RGB filter will increase light/photon pass to the sensor. in theory, this will increase DR assume M11 and M11M share the same read noise.

However, M11 ISO64 vs M11M ISO125 means M11M can't take advantage of increased signal level at low ISO. Put it in another way, without RGB, M11M have more signal pass through. However, ISO64 of M11 means it can take one stop extra light/signal to offset its RGB filter loss. Hence we see similar DR for both which make sense.

At low light condition, (high ISO). Less signal loss due to no RGB filter clearly show M11M advantage. Due to less light loss, the exposure time can be reduced for M11M, read noise will be reduced so that M11M have about 1 stop DR benefit.

Having said that, I feel M11M benefit is more to the pixel level fidelity (if you pixel PP) than DR as I feel modern cameras's DR are really good enough for a while now.

Apr 16, 2024 at 04:05 PM

  Previous versions of thrice's message #16525227 « Leica M11 Monochrome Dynamic Range »


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