ADX tone corve specification

adx
Tags: #<Tag:0x00007f6dba062d20>
(Daniel Plappert) #1

Hello all,
I’ve been browsing some standards, however, I haven’t found one that unambiguously defines the equation to go from transmission (as seen by the scanner sensor) to the density value. Once you have the density value, ST 2065-3:2012 takes care of the rest, but getting the density value is the interesting bit here.

Of course a log10 of the transmission value would make sense, but it appears that in practice, it’s more complicated than just a straight log10. For re-linearising an ADX-encoded image, Baselight and the ACES ADX code do different things. At the end of the day, the two approaches may deliver similar results, I haven’t checked yet.
It would be fantastic to see the spec which those two very different snippets of code derive from (if they indeed derived from a spec in the first place). Does anyone know which standards document to refer to?

all the best,
Daniel

(Scott Dyer) #2

The definition of Academy Printing Density is specified in ST 2065-2:2012. Specifically, the spectral calculation equation from transmission is in Section 5.2.3.