My point was that he would have ask the evidence of what those laboratory measurements are saying on the real result. You can actually apply the zone system with any camera, regardless of its specs. It's a shooting and lab technique.
Indeed. One should always question the evidence if it seems unbelievable or contradicts other information. I do it myself frequently. You
can apply the zone system with any camera, but only part of it. Most film on smaller formats cannot capture the entire dynamic range of Ansel's zone system, which covers about 10-11 stops of DR. Ansel used large format B&W film for good technical reasons.
You can't compare a technical system that is used on the field for practical purpose with a clear aim with a spec data in a webpage.
Yes you can. I've done it. I mentioned before that I took some trouble comparing my 5D with the new Nikon D3 shortly after it first came out, when I was in Thailand. I spent half a day travelling to and fro, across the city of Bangkok, to check for myself these extraordinary claims of high-ISO performance for the D3. I simulated the high ISO settings that the 5D doesn't have (but the D3 does have), by underexposing the 5D by various amounts at ISO 3200.
After examining a hundred or so RAW & jpeg images taken above ISO 3200, I came to the conclusion that the high-ISO advantage of the D3 was in the order of 2/3rds of a stop, half a stop at the most.
My procedure was to match images from each camera that had equal ETTR exposures (after adjusting the histogram for the 5D to simulate an ETTR), then examine detail and noise in the shadows. Since both cameras are of the same format and have a similar pixel count, the 5D having just slightly more pixels, that procedure worked well.
If the DXOMark website had existed at that time, I could have saved myself a lot of trouble, because their laboratory tests show a similar result. They didn't test beyond ISO 3200 with the 5D, but the slope of the graph is clear.