Discussion in 'X-Pro2 and X-Pro1' started by (c)ow, May 18, 2017.
Thanks for the details!
some interesting points here, ysarex! Curious if you've discussed them with Rico at any point and where your information comes from. The point about camera manufacturers ISO ratings being specifically linked to the JPEG output is not something I was aware of if indeed correct. I make no claims myself to be technical and have no bone to pick either way.
The ISO standard was updated in 2006. At that time the committee basically accepted the CIPA (Camera & Imaging Products Association) standard for digital cameras as an addendum. The CIPA standard is detailed here: Please login to view links -- download standards doc DC-004. The ISO standard then in fact allows for variable methods to determine an ISO value but the new 2006 "Standard Output Sensitivity" measure has been universally adopted by the people who wrote the standard (see CIPA members list: Please login to view links). The wiki article on film speed (Please login to view links) has a good explanation of SOS: "The Standard Output Sensitivity (SOS) technique, also new in the 2006 version of the standard, effectively specifies that the average level in the sRGB image must be 18% gray plus or minus 1/3 stop when the exposure is controlled by an automatic exposure control system calibrated per ISO 2721 and set to the EI with no exposure compensation. Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically JPEG—and not to output files in raw image format." Make note of the qualifying clause that begins the 2nd sentence.
So does this matter to us? Basically SOS effectively uncouples ISO from any hard measurement (the sensor). SOS hands the camera manufacturers free reign to adjust ISO to any desirable extent via the processing software in the camera. They do so to varying degrees liberally or not which then begs the question; what's the ISO of the sensor in the XP2 or any digital camera for that matter?
P.S. No bone to pick here either -- just trying to help with accurate info.