Do you have a Gretag Macbeth Color Checker or even a 8 x 10" gray card? If you do and if you can find the time, maybe shoot a full frame (covering the whole card) of both and share the MEFs if you can. Exposure need to be as accurate as you can get it. Then you can start to stop down by 1, 2, 3, 4 stops etc and then over-exposed by 1, 2, 3, 4 stops etc. on the gray card. If the ZD is having any issues with the sensor reacting to over or under exposures, I think it will show very clearly in one of those shots. Game to give it a try?
Color checker and gray card would be useful to have! When reading your post last nigh I meant to drive in morning to nearest place to buy them about an hour away, but rain this morning made me lazy! Instead I took the gray side of my Domke wrap, a slightly off white board and a large flat neoprene pouch and posted on a wall. That is a simulation of what you suggest .
Conditions were following:
Diffused light on subjects from large windows behind my back and cloudy sky just before noon time.
80mm f1.9 at f22 and about 70cm away from subject.
Processing in SilkyPix
Film color V2 to give more saturation, in order to MAGNIFY any problem.
Shooting photos with exposure compensation -3, -2, -1.5, -1.0,-0.5,0,+0.5,+1.0,+1.5,+2.0,+3.0 Then doing reverse by compensation in SilkyPix.
Off white showed nothing.
Gray showed nothing.
However, at black neoprene I got results as attached, 100% crops.
Of course, PLEASE NOTE: I very rarely use Film color V2 because it makes too overly saturated photos, AND SilkyPix in their manual recomments to individually desaturate specific colors when using such overly saturated color setting.
THIS IS SIMPLY ONLY A TEST OF THE SENSOR.
Is what we see normal? Is this normal noise?
To magnify the issue further in order to make it more visual, in addition to color setting V2 I also slid the saturation adjustment to max +3. PLEASE NOTE: doing same on a normal photo with colors would result in very overly highly radiant saturated colors. Again this is only a test for the sensor!
With above in mind, is my sensor acting normal???
I should say that having spent so much more on a camera than my D200, I did not expect this condition. Yet, the test is EXTREME conditions, so with that in mind is this normal to expect from a medium format sensor?