"Sensitometric behaviour" of image sensors.
This is a fairly technical question but I hope someone will be able to throw some light <G> on it!
Film has a sensitometric curve (the D logE curve) that is non-linear: it has a gentle toe, with the slope of the curve (i.e. the contrast) increasing at the mid-point of the exposure range and then decreasing again at high exposures (the "shoulder"). This is what made film fairly "forgiving" and these curves were exploited superbly by Ansel Adams in his Zone System. Indeed he developed his films individually to make the film curve fit his subject brightness range!
I'm making the assumption that a digital image sensor characteristic is basically a straight line between full black and a highlight at which it starts to clip. (Is that correct?). No gentle toe or shoulder, just "hard clipping" at the extremities.
I also presume that HDR techniques aim to emulate the gentle toe and shoulder.
My last question (as it applies specifically to the Nikon) is:
If I choose the lowest contrast possible in my Picture Control, does that enable the sensor to cover a greater dynamic range? Or does it keep that fixed but just reduces the contrast?
Mold, Wales, UK
D300, D200, OM1, OM2n, Bronica ETRSi, Lumix LX5
#2. "RE: "Sensitometric behaviour" of image sensors." | In response to Reply # 0dm1dave Nikonian since 12th Sep 2006Mon 31-Aug-09 04:29 PM
With digital we recreate that tone curve when we adjust Levels and Curves or load a custom curve (or set picture controls) in the camera.
HDR is still linear but you are just expanding the dynamic range beyond what the camera can record in a single exposure. You still need o adjust tone curve after combining exposures to create pleasing tones.
>> If I choose the lowest contrast possible in my Picture Control, does that enable the sensor to cover a greater dynamic range? Or does it keep that fixed but just reduces the contrast? <<
First your camera settings only matter if you shoot JEPG, TIFF or if you use Capture NX to convert your NEF files. If you shoot NEF and use any other program to develop the NEF the camera settings, including contrast, are ignored.
So setting the contrast will not increase the dynamic range of the sensor but it could help you evaluate to exposure, particularly the highlights, especially if you try to “expose to the right.”