Thanks Eleanor, I’m not really a pixel peeper and I’m only reporting what I have read elsewhere – Yes, I would agree with you that your iso50 300% image shows finer resolving detail in the mid-tones and also the shadows than your iso100 300% image but then that’s what I would have expected anyway from either the A7R or the A7RII, with the reduced noise from 1 stop lower iso....The problem as I see it lies still at what’s going on at the other end with blown highlights...If you are having to blow out the highlights deliberately in post processing in C1 (on the iso50 image) then it’s quite feasible that you probably could have exposed the highlights further still to the right at the taking stage on the cameras histogram and still got away with it....The only real way to test this as far as I can see is exactly as Jim Kasson explained here
http://blog.kasson.com/?p=11622 or how DPReview did it under a controlled lighting set-up and with a Stouffer step wedge (
http://www.dpreview.com/reviews/Sony-alpha-a7r/14 )...
Quote
“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)”
The gentle curve of the shoulder shows subtle finer highlight detail being retained at iso100 whilst the iso50 comes to an abrupt halt and blows out 1 stop faster.
Please see bottom graph iso50/iso100 comparison
http://www.dpreview.com/reviews/Sony-alpha-a7r/14
According to DXOMARK...Both the A7R and A7RII cameras have fake iso’s below iso100
DXOMARK see A7R iso50 and iso100 sensitivity are both the same...
http://www.dxomark.com/Cameras/Sony/A7R---Measurements#tabs-2
DXOMARK see A7RII iso50 and iso100 sensitivity are both the same...
http://www.dxomark.com/Cameras/Sony/A7R-II---Measurements
As said earlier I’m only reporting and linking together what others have said before me...I still have a couple of Stouffer step wedges lying around somewhere from the good old film days
I should really test this out for myself.
When I shot with my 35mm Film Leica M’s in the 80’s I was happy with Tri-X and then later with TMax3200 developed in a dilute high acutance developer to exaggerate the grain to it’s utmost point just before Mackie lines began to kick in but when I was shooting Large Format sheet film (14x11, 10x8 and 5x4) I did the very opposite, I tried everything possible to make that grain disappear...Pyrogallol and Pyrocatechol film staining developers contact printed on Silver Chloride (Kodak AZO paper from Michael A. Smith) developed in Amidol. Nowadays I don’t mind a little noise in my digital images as you may have already gathered
...Cheers Barry