Camera spectral sensitivity data

Hardware
,
1

Reading Spectral emissions from modern light sources (more graphs added) reminded me of rawtoaces.

The RAW to ACES Utility or rawtoaces , is a software package that converts digital camera RAW files to ACES container files containing image data encoded according to the Academy Color Encoding Specification (ACES) as specified in SMPTE 2065-1. This is accomplished through one of two methods.

  1. CameraRAW RGB data (generated by libraw) is converted to ACES by calculating an Input Device Transform (IDT) based on the camera’s sensitivity and a light source.
  2. CameraRAW RGB data (generated by libraw) is converted to ACES by calculating an RGB to XYZ matrix using information included in libraw and metadata found in the RAW file.

The output image complies with the ACES Container specification (SMPTE S2065-4).

rawtoaces uses one of three methods to convert RAW image files to ACES.

  1. Camera spectral sensitivities and illuminant spectral power distributions
  2. Camera file metadata
  3. Camera data included in the libraw software

The preferred, and most accurate, method of converting RAW image files to ACES is to use camera spectral sensitivities and illuminant spectral power distributions, if available. If spectral sensitivity data is available for the camera, rawtoaces uses the method described in Academy document P-2013-001 (.pdf download).

While preferred, camera spectral sensitivity data is not commonly known to general users. When that is the case, rawtoaces can use either the metadata embedded in the camera file or camera data included in libraw to approximate a conversion to ACES.

Examples of such data could be found here: rawtoaces/data/camera at master · AcademySoftwareFoundation/rawtoaces · GitHub.

2 Likes
2

@afre, you are The Man!! I’ve been looking for such for my camera for a couple of years, and there it is, for the Nikon D7000. Something to mess with… :smile:

1 Like
3

@afre Is there any reasonable way you know of to measure spectral sensitivity data for a sensor that’s not in the list? And alternatively, how can I find out if my sensor may be identical to one present in the list?

4

I don’t know enough to speak on that. Start here: https://acescentral.com/t/rawtoaces-calling-all-developer-types/1048.

5

not sure if reasonable… if you want to build some device yourself, this might be a good starting point:

https://www.hdm-stuttgart.de/open-film-tools/english/publications/OFT-SpectralDatabase.pdf
https://www.hdm-stuttgart.de/open-film-tools/Publikationen/ProjectSummary.pdf

i have to say i’m excited about rawtoaces… even though it seems to be in very basic shape at this point (do i read the source right that they use the great spectral input to create a matrix ??).

6

I share your excitement but these are still early days.