How to open with technical flat calibration in 7.0

Question

In earlier versions, Camera Raw gave an option to set "Blacks" = "Brightness" = Contrast" = "0", and set a straight tone curve.  With color space set to Adobe RGB, this opens with EXACTLY a calibrated power of 2.2.  This gives a very flat looking image with no "S" curve that no one would use for beauty, but when used for SCIENTIFIC applications, I can raise the 16-bit image to the 2.2th power in Photoshop and have EXACTLY a linear correspondence between photon count and pixel count.  This lets me add photons, divide images to normalize, make exact pixel by pixel measurements, and a lot of things us scientists like to do unrelated to making pictures beautiful.
Camera Raw 7.0 changed the sliders, and after hours of scientific experimenting I can not find a combination that opens images that are technically exactly flat (gamma 2.2 of course) without deviations to the straight curve.
I do weddings occasionally, science mostly, and Photoshop is my go-to tool for both.  Thanks in advance for your help advancing the cause of science.

Answer 1

Thank you so much to both Jeff and Noel, you gave me a warm feeling of community in my struggles.
Noel, of course you are right, I didn't know about that.  That explains why, if I adjusted a DNG flat in 6, then opened it in 7, it would come up with the old sliders in place.  It opens exactly the same in 7 when I choose 2010, right down to the bit level.
Jeff, I have been learning how to use the DNG Profile Editor you recommended.  When I build a profile  with a linear tone curve and apply it under 2010, all the sliders are left as default, even the "S" tone curve, EXCEPT "Blacks" needs to be set off the default to "0".  When applied under 2012, all the sliders should be set to default EXCEPT Whites to +25 and Blacks to exactly +25.  Even then the highlights are a little different, I haven't measured yet to decide if they are more or less accurate.
To others in the scientific community:  Even opened linear like this with Adobe RGB (and even extended ProPhoto RGB) there can still be issues with colors going negative, and false colors in highlights as some channels saturate before others.  You can use Adobe DNG Converter to do the dematrixing by choosing Custom > Linear(demosaic) and Uncompressed.  Then "open as" the resulting file in "Photoshop RAW" mode, also known as "RAW RAW" (not camera raw), and choose the appropiate sizing parameters.  With a little trial and error you can get at the raw data right out of the sensors, exactly as it was recorded, except demosaiced.  (If you deselect Linear but keep Uncompressed checked in DNG Converter and open as a single channel, you can actually get under the Bayer array.)  The problem is you are on your own with the tone curve, and some cameras have really weird piecewise linear protocols that can't be described in a continuous equation.  And all metadata is lost in RAW RAW format.  It is probably an impossible dream to wish that Camera Raw could give the straight data off the sensor, calibrated only for gamma 2.2 tone curve.  Such a mode would have no setting for exposure or color temperature as it would always show the full saturation range for each sensor.  Images would look dark and greenish because for a very good reason red and blue sensors are designed to be less sensitive than green.