The two shots are quite good comparable; the Canon's exposure is about 1/3 stop lower than that of the P30+. That's very good (in a test in controlled situation one would have to make several shots with both cameras 1/3 stop apart and select those, which are the closest).Note:
the histogram shows, that ISO 100 on the P30+ is "fake", it is the numerical derivative of whatever. I don't know if this fact had any influence on the result. One would have to create a serie of images to find out, which is the base ISO.
It is important to know, that in ACR
- the P30+ shots gets adjusted by -1 EV,
- the 1DsMkIII shot is adjusted by +0.35 EV.
These adjustments are not visible on the "Exposure" slider. In order to go back to the origin, the P30+ image has to be adjusted by +1 EV and the 1DsMkIII image by -0.35 EV.
After this reverse-adjustment and picking WB on the white or grey card, the RGB values on this card reflect the small true difference in the exposure; replacing the -0.35 EV by -0.15 EV equalizes the exposures.
Anyway, Rawnalyze is more suitable for analyzing them. It shows, that the level of noise in terms of standard deviation is virtually identical
in these images, measured on very dark, smooth areas. However, I find the P30+ better on such areas subjectively.
Screen captures of the histograms and of different displays are in this, 3MB large layered TIFF
Note, that Rawnalyze displays the *raw* data. There is no noise reduction, etc. except for what is unavoidable, namely black level compensation on the 1DsMkIII image. I picked WB on the white card in both images; that changes the RGB values, and it was necessary to make the standard deviations comparable. The raw values are not comparable directly, as the pixel values of the 1DsMkIII are between 0 and 14256, and of the P30+ between 0 and 65535.
I explain the captures only if someone is really interested for that.