Quantifying dynamic Range – #5 by priort – Processing

I use a grayscale step image I created from a series of ISO 100 Expodisc exposures on my A7III. The lightest patch is where the green (and red/blue after white balance scaling) channel is just barely clipped and each patch below that has 1 stop less exposure. I combined center crops from white balanced 16 bit linear conversions and numbered the patches with reference to the camera’s full dynamic range potential according to the photon transfer curve from photonstophotos.net.

When you use the waveform scope it’s incredibly simple to see exactly what is happening in terms of dynamic range; e.g., here’s what the it looks like with no exposure changes or sigmoid (scope is showing it in sRGB gamma):

Here it is with sigmoid defaults:

and here you can see Sigmoid (with ACES 100 nit like preset) making use of 100% of the camera’s full dynamic range when exposure is scaled so that the camera’s “film-like” zone 5 is corrected to 50% luminance. The darkest patch is RGB 1 and the brightest is RGB 254. Perfect full tonal scale exposure according to Ansel Adams : )