ACR Defaults and Dynamic Range

Question

The tone curve in ACR has a profound effect on the dynamic range of the rendered image, and often this is not appreciated by users. To demonstrate the effects of the tone curve on DR, I photographed a Stouffer step wedge with the Nikon D3 and rendered the image into a TIFF with various tone curves and determined the resulting dynamic range with Imatest.
Here is the target rendered with the ACR defaults for this camera, which include a black point of 5 (downsampled and shown as a JPEG):
http://bjanes.smugmug.com/photos/422699368_FRdKT-O.jpg
Shown below is the resulting characteristic curve as determined by Imatest along with the DR and other data. The total dynamic range is only 7.64 stops. This low DR results from the default black point of 5, which rolls off the darker tones as shown on the graph.
http://bjanes.smugmug.com/photos/422697342_tnUFo-O.png
By setting the black to 0, the total DR is increased to 12.3 stops and the useful photographic DR according to various quality levels is shown.
http://bjanes.smugmug.com/photos/422697338_5e8pv-O.png
One can also use a linear tone curve by setting all the basic settings to 0 and the point curve to linear.
http://bjanes.smugmug.com/photos/422697332_u59B5-O.png
For convenience, the tone curves are shown together here.
http://bjanes.smugmug.com/photos/422697328_26BFV-O.gif
One might wonder why Adobe chose a default black value of 5 for the D3, since it severely limits dynamic range by rolling off the blacks. The probable answer is that the full DR can not be reproduced on screen or in print without using a tone curve that would give the image a flat and unattractive appearance. Note that the darker steps of the Stouffer wedge are not distinguishable on the screen but differences can be noted if one measures the values with the eyedropper in PS. The default setting of 5 rolls of shadows which would not be reproduced and enhances contrast in the remaining image.

Answer 1

>Why? Real World Camera Raw is platform agnosticaside from the fact that most all of the images contained in the book happen to come from cameras Bruce and I had/have and those are Canons. To the best of my knowledge, there is nothing in Camera Raw that is camera model dependent except for the DNG Profiles and the baseline demosiacing and noise reduction which vary camera by camera. Why should I care about the Nikon D3 specifically?
In 35 mm style dSLRs (which I would venture to say are used by the vast majority of ACR users) Nikon and Canon are the two major brands. One thing that is camera specific is the baseline exposure offset that ACR uses for these cameras. For the Nikon D3 (and other recent Nikon cameras), ACR uses a baseline exposure offset of +0.5 EV. If you don't know this and try to expose to the right as much as possible, the histogram will appear overexposed in ACR when in reality the channels are far from clipping.
This is demonstrated in the following screen capture using ACR defaults with an Exposure value of 0. The highlights of the target appear blown.
http://bjanes.smugmug.com/photos/423897106_wvzqw-O.png
They also appear blown using the new beta profile, which does not take the baseline exposure offset into account.
http://bjanes.smugmug.com/photos/423897066_xeHoi-O.png
Looking at the raw histogram with Rawnalize, we see that the channels are not blown:
http://bjanes.smugmug.com/photos/423898181_md3kC-O.png
And here are the actual raw values for the red, green and blue channels (highlighted) of Step 1:
http://bjanes.smugmug.com/photos/423901972_MguxL-O.png
The raw headroom in each of the color channels (as shown in the raw histogram) also has something to do with the amount of highlight recovery that is possible. I would think that these considerations would be of inerest to the readers of your Camera Raw book.