Just tested the studio tool with the D4s and the NEX-5T (a fairly modern APS-C/DX camera), and found that their ISO capacity did vary that much:
I selected incandescent light, and the patch of greenery in the upper right corner. Set the ISO to 102400, which the 5T can’t follow, so stopped at 25600, and as far as I can see (I use a calibrated iMac) there was little difference in noise, at that setting. Menas a camera that costs maybe a tenth of the D4s can deliver almost the same image quality, just two ISO steps behind!
Tried the D610 as well, but that doesn’t go any further either, but seems to be just one ISO step behind, at less than half the cost! Lowering the D4s to 51200 gives a very similar result, if not the same color balance!
An amazing camera in many ways, this new D4s, but had I the money to buy one, I’d buy a RX1R, and throw a party!
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.