Pushed ISO: Let's make it clear

Friday, February 04, 2011

Camera Article
ISO and exposure | RAW ISO values: The fundamental basis for accurate comparisons | RAW ISO measures are inferior to manufacturer ISOs: is this a problem?

RAW ISO values: The fundamental basis for accurate comparisons

A fair way to compare sensors is to assure that the shooting conditions are the same (same scene illumination, same exposure time and same aperture) and that the exposure of the output image is also the same. If these factors are the same, this will mean that the ISO sensitivity is the same at RAW level.

Thus when DxO Labs measures the performance of a sensor, we always link measurement results with exposure and then to real sensor ISO sensitivity.

Once determined, RAW ISO allows for accurate comparisons. The dots are placed at the corresponding ISO value that shows the actual manufacturer nominal value. If the curves had been based on the JPEG ISO, the gaps would be much higher… but totally artificial and biased.