Olympus mirror-less ISO (RAW) vs DXO

Started Aug 30, 2014 | Discussions thread
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Leo Veteran Member • Posts: 6,292
Olympus mirror-less ISO (RAW) vs DXO

I am sure it was discussed, however I could not find it - sorry.

DXO in sensor testing section shows that the Olympus actual camera ISO is approximately half of the camera set ISO.  In other words, when camera set ISO is 800 the actual camera ISO is approximately 400.  I have tried to test it and it seems that my test failed or Olympus cooks RAW file.

My test: I have photograph an 18% Gray Card at several set ISO in Aperture priority mode with the exposure compensation set to 0EV and then the second set with the compensation set to +1EV. The camera was set to RAW.  Then I have opened the images in Lightroom and checked the histogram and the RGB values.

For the compensation set to 0EV the RGB readings were 50% +/-2% and for the compensation set to +1EV the RGB readings were measured as 70%+/-3%.  The results indicate that the I do not understand DXO test results or Olympus cooks RAW files.

The article "How high can your camera fly? We present our 2014 High ISO 8 x 10 print showdown - Updated 7/16/14", published by imaging-resourse.com for the test of selected cameras at ISO 3200 and above in the test for ISO 3200 set all cameras for ISO 3200 except Olympus cameras, which were set to ISO 6400!

The same happened

to Sony A58 at ISO 3200

to Fuji X-T1 at ISO 6400

to Nikon D800 at ISO 12,800

Here is the link:


Please help to understand the Olympus ISO philosophy, its effect on the image quality and the best method to select ISO and compensation for RAW shooting or post a link to a format discussion of this subject. My search did not work.


 Leo's gear list:Leo's gear list
Pentax K-S2 Pentax smc DA 16-45mm F4 ED AL HD Pentax DA 55-300mm F4.0-5.8 ED WR
Fujifilm X-T1 Nikon D800 Sony SLT-A58
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