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Author Topic: I still wonder about ISO score  (Read 1627 times)
thalas
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« on: December 22, 2012, 03:17:48 PM »

This a comment for this page on the website
I still wonder about ISO score,
Every one know that a99 and d600 are using same sensor.
Even dpreview still proved these two got same ISO score which are better than D800E and 5D MK III.
Why A99 on DXO got ISO score only half of D600?
This gap is too big. Could you let readers know?
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a odd guy
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« Reply #1 on: December 22, 2012, 05:10:30 PM »

It's just effective ISO sensitivity magic!
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Even if you criticize me,I could never understand what you mean.
podchong
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« Reply #2 on: December 24, 2012, 06:01:39 AM »

Because of the SLT effect.
Please read about SLT technology and you will known why.
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thalas
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« Reply #3 on: December 26, 2012, 02:33:17 PM »

I knew about SLT technology.
Only thing I want to know is Dpreview gave same iso score for a99 and d600, but DXO gave it totally different.
who is better accurate ? which one i should believe? why its so different?
I didnt meant to begin some conflict, everyone knew DXO and dpreview are best of the best camera measurement. I was expecting these two website give similar iso score. That's all.
 
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thalas
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« Reply #4 on: December 26, 2012, 02:47:29 PM »

btw, as below comment u said that because a99 using phase detection AF system so it will need more light which effect ISO score. If this is correct why you use this system during measurement since other camera have no this phase AF system. So it different standard of measurement, Am i right ? 

Here what i guess, dpreview might not use phase AF system during measurement but DXO did. That why DXO got a lower score when compare to D600 since this phase AF system need more light but Dpreview got same score of A99 and D600.
If this is right, DXO may need to do measurement again without using phase AF system
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Revenant
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« Reply #5 on: December 28, 2012, 12:56:07 PM »

DXOMark's definition of the Low-light score: "Thus low-light ISO is the highest ISO setting for a camera that allows it to achieve an SNR of 30dB while keeping a good dynamic range of 9 EVs and a color depth of 18bits."

That is an arbitrary definition of the highest ISO that gives excellent image quality in an 8Mp print. DPReview don't use this criterion, so there is nothing to compare between the two sites in this regard.

Furthermore, they use two different definitions of ISO. DPReview use the standard definition in the industry, which is based on the brightness of out-of-camera JPEGs. This definition isn't applicable to unconverted raw files. It's the same definition that's used by the camera manufacturers. DXOMark, on the other hand, analyze unconverted raw files, and therefore use a definition of ISO based on sensor saturation.
This causes some confusion among people, who assume that all review sites measure the same thing. You often come across people accusing the camera makers of "cheating" with ISO, because ISO 1600 is really only ISO 800, for example. But they are comparing numbers measured in different ways, and there is really no cheating going on at all.

The point of all this is that DXOMark and DPReview coming to different conclusions about the ISO performance of a camera, is no cause for alarm, because they aren't talking about the exact same thing.
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