Calibrating a camera is a complex operation that requires several steps:
- Reading RAW format: RAW files are generally stored in undocumented proprietary fomats, which often requires us to do “reverse engineering” work in order to extract all the useful data.
- Measuring the sensor: We particularly measure the sensor’s colorimetric response under different illuminants, and noise at all sensitivity settings. This operation generally necessitates more than a thousand shots which must then be validated and transformed into usable data for DxO Optics Pro.
- Studying the rendering of the JPEG engine: To provide you with a default rendering that comes as close as possible to the JPEG files that your camera generates, we study the way that your camera interprets RAW data, and we try to reproduce that interpretation as accurately as possible in terms of color and contrast.
Note that this last operation is very different from our goal in studying the sensor’s colorimetric response: when studying the sensor, we are looking to find the correspondence between the colors that the sensor captures and the true colors in the scene. When studying the JPEG engine, we are looking to find the correspondence between the colors that the sensor captures and the colors in the files that the camera generates.
As it turns out, camera manufacturers generally do not try to build in 100% color accuracy, but instead introduce certain color variants that lend particular “renderings” to different camera brands. This creates interminable debates among photographers who want to know if, for example, the “Canon rendering” is better than the “Nikon rendering,” and vice-versa.
Obviously there is no good answer to this type of (largely subjective) question, but our goal for our calibration work is to preserve each rendering (so dear to photographers regardless of their preferred brand) so that they will see the same rendering after RAW processing as contained in the “original” JPEG files. This calibration also gives you the ability to choose the rendering you would like to apply to your photos — whether it’s a “Canon rendering” or a “Nikon rendering” (or vice-versa!), or other camera rendering.