Re: What is Equivalence

I think there's some reason to suppose that they aren't. For instance, both Nikon and Canon switched from SOS to REI and there wasn't a surge of comments from experienced users that the metering had changed. DPReview tests meter calibration according to SOS, and they didn't report that REI cameras were out of calibration. One wonders why a camera company would calibrate their meter differently.

Multi-zone metering

This mode is also called matrix, evaluative, honeycomb, segment metering, or esp (electro selective pattern) metering on some cameras. This metering mode was first introduced by the Nikon FA and was termed Automatic Multi-Pattern metering.

en.wikipedia.org/wiki/Metering_mode

Essentially by the same factor. The difference between 78 and 10 is that Saturation used 100% lightness and SOS 18% as the reference point. The resultant ISO should be the same for a pure sRGB gamma curve. But whatever, so long as the ISO method is the same, the ISO is inversely proportional to exposure.

Interesting, because unless you adjust your technique and processing with some quite deep knowledge of how your individual camera works, differences in DR won't make a whole load of difference to your results. There's a good reason why years of deficiency in DR didn't hurt Canon's sales too much.

Does the frame size affect your exposure decisions, and if not, why not?

I don't think that has a lot to do with DR per se, it has to do with lower read noise, and depending on how you respond to the second question, to do with getting more light energy into the image.

What I was asking was how you make your exposure decisions when using the different cameras. I'm still not sure what you are thinking of as 'DR'. The D7000 has just shy of 14 stops of DR, the Z7 just over. I very much doubt that unless you have a really coherent and meticulous methodology for setting exposure and processing your photos you're using anything close to that - so DR really shouldn't be an issue between those two cameras. D50 is a somewhat different proposition.

I'm not sure I quite understand what you were doing there, Jim. If I understand correctly, the figures you're getting are the raw numbers? How can you relate those directly to 'sensitivity', and what are you calling 'sensitivity'?
I'd add on your caveat - "I don’t know which camera has the most accurate ISO setting. In fact, as far as I’m concerned, what with all the ways a manufacturer can rate the ISO sensitivities of sensors, I’m not sure that question has much meaning." - of course a camera manufacturer does not rate the ISO 'sensitivity' of its sensors - there is no 'ISO' of a sensor. ISO only applies to processed output, and the effect of ISO setting on the raw file is not mandated.
Interestingly, the QE appears to be in reverse order compared with this 'sensitivity'.

'Relative responsivity'? I can see it's nice to know which raw numbers result from a given exposure.

I think there's likely not a lot in the former, a smaller sensor likely makes IBIS a bit more energy efficient, rather than easier. The 'faster readout' thing assumes that wire delay is a bottleneck in readout speed, which it isn't. The reverse is likely true for global shutter. Global shutter requires more circuitry in the pixels, which is easier in a bigger pixel.