Luminous Landscape Forum

Raw & Post Processing, Printing => Digital Image Processing => Topic started by: Guillermo Luijk on January 09, 2015, 05:10:04 am

Title: Camera tone curve reverse engineered
Post by: Guillermo Luijk on January 09, 2015, 05:10:04 am

I felt curious time ago but until now never reverse engineered the tone curve applied by the camera to build the JPEG. The camera was a 350D and quite neutral parameters. This is how the RAW file and its histogram evolves at the different stages:

1. Pure RAW data
2. Linear neutral RAW development (camera WB, sRGB)
3. Same as 2 plus sRGB specific ~2.2 gamma curve (image appearance remains unaltered, histogram expands)
4. Camera JPEG (image bright and contrast are incrased)

(http://www.guillermoluijk.com/misc/procesoraw.jpg)

The translation from 3 to 4 corresponds to the following tone contrast curve:

(http://www.guillermoluijk.com/misc/curva.png)


Hope you find it interesting.

Regards

Title: Re: Camera tone curve reverse engineered
Post by: thierrylegros396 on January 18, 2015, 02:16:38 pm

Differences between the 3 curves correspond to sensor "calibration"?

Title: Re: Camera tone curve reverse engineered
Post by: Eric Myrvaagnes on January 18, 2015, 05:10:55 pm

Fascinating, Guillermo.