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What make 20 a magic number than 5 or 10 in score.
My 6d have grand total score of 69, which 20 below a900, so it is bad, and 5diii is 79, 10 point less than a900, so it is not bad, but now my 6d is only 10 point below 5diii, then my 6d must not bad as well
Basically, you were saying all current camera having same performance is this regard. I disagree, but I agree we should not take this number as sole indication but a good reference.
I believe 5 point between RX1 and RX1R is...Show more →
The magic is in "noticeable difference". I'll short that to JND from here on to abbreviate.
Your sample is a regression sample - if 90 isn't a JND from 80, and 80 isn't a JND from 70, and 70 isn't a JND from 60, and 60 isn't a JND from 50 - does that mean that 50 isn't a JND from 90 No, not really...
The thing with color is that it isn't something you can put "one number" on. That's almost impossible in theory, and definitely impossible in practice.
Two cameras can have the exact SAME score, and behave quite differently.
One may be correctable by a good profile, the other maybe not.
One may have all errors in gree-blue, the other in green-red - that'll give very different results in an image, but not in the score.
But in the metric that DxO uses, 20 is a definite "this camera will not be able to give as accurate color, even with a very good camera profile" limit.
Second that about the Sony A900. It has the most correctable [by profiling] and most pleasing [just my personal opinion] color rendition of all cameras I've tried/owned (I had the 850).
Color isn't just about hue and saturation! A color rendition is also what brightness value a color is assigned, and the balance between those three are wildly different even with almost otherwise identical sensors - as users of many similar cameras know. Even with an almost perfect camera profile, there's still some small differences left. Interactions between CFA and raw converter, interactions between noise factors before/after a profile has been applied and so on.
But a good camera profile, in good quality light (not cheap office fluorescents) will make most cameras almost unseparable by "only" doing visual inspection, for an untrained eye.