Our Dynamic Range measurement system involves shooting a calibrated Stouffer Step Wedge (13 stops total range) which is backlit using a daylight balanced lamp (98 CRI). A single shot of this produces a gray scale wedge from the camera's clipped white point down to black (example below). Each step of the scale is equivalent to 1/3 EV (a third of a stop), we select one step as 'middle gray' (defined as 50% luminance) and measure outwards to define the dynamic range. Hence there are 'two sides' to our results, the amount of shadow range (below middle gray) and the amount of highlight range (above middle gray).
Yep - JPGs. Actually, for their JPGs, I'm not sure if they use an in-camera conversion or use ACR to convert RAW files. In some reviews they do present an additional analysis of 'RAW headroom' where they push and pull the exposure a bit in ACR (which, I'd argue, is not the best software to use for the 'analysis' since ACR does some 'black box' adjustments).
The other issue is with the statement, "...from the camera's clipped white point
." They don't say, but I'd assume they determine the clipped white point in the easiest way, by using the histogram and/or highlight warning on the LCD review. Many people claim that they can safely ignore settings like white balance, Picture Style, ALO, etc., because they shoot in RAW, and none of those settings affect the RAW image data, only the metadata. That's technically true, but there's a caveat. When you make an exposure decision based on the histogram on the rear LCD, the luminance data plotted in the histogram aren't derived from the RAW file, they are derived from the JPG preview image generated within the RAW file container (and that image is shown on the rear LCD as well). All those settings that 'dont apply to RAW files' do
apply to the JPG preview image, and thus to the histogram you are using to assist with your exposure decisions. Thus, since in effect they're using ETTR (for the most transmissive section of the Stouffer wedge), the right side of that histogram might not be far enough to the right.
Actually thatÂ´s (imho) closer to reality then the 12-13 Stops from DXO Mark.
8.x EV (9.x with Raw Headroom) seem to be what i can achieve with my 1D MK4.
But i sure come nowhere near the 12 Stops from DXO Mark.
but you canÂ´t pull 3-4 stops out of a RAW and that is the difference between the two tests.
Despite their flaws, the DPR results are, indeed, closer to real world results. DxOMark's data are accurate, and based on careful empirical testing of the RAW file data, not whatever the camera or ACR do to that data. But the machine-detectable threshold that separates signal from noise is not the same as the human visual system's threshold. I think the DxOMark data are like the EPA estimates of fuel economy on new car stickers and the download speed estimates provided by wireless carriers - useful for relative comparisons of models tested in the same way, but you'll never get those values when you're driving your car or downloading a video.