Dxomark "measured" ISO vs Manufacturer ISO

Started Jan 7, 2013 | Discussions thread
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ET2
ET2
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Dxomark "measured" ISO vs Manufacturer ISO
Jan 7, 2013

This was in a response to "Endos" in another thread, but this thing just keeps coming up years and after years.  It's basically same people who look at dxomark's "measured" ISO and think that some cheating is happening by camera companies ...  (even though they have been told that dxomark measured ISO is not a standard definition).

Now watch this ...

Here is Dxomark graph for EPL1

Manufacturer ISO: 200 -- Dxomark measured ISO 124

Manufacturer ISO: 100 -- Dxomark measured ISO 124 STILL THE SAME!

How on earth is that is possible? If anyone has EPL1 (I used one a while ago) and if you change the ISO from 200 to 100 on the camera, you will see that the shutter speed slowed down by a stop, but yet dxomark "measured" ISO remained the same. The shutter speed changed (check it on your camera if you have Oly camera) by dxomark measured ISO remained the same!

That's a proof positive tha dxomark "measured" ISO says nothing about exposure, shutter speed or anything else. Dxomark "measured" ISO is based on highlight clipping. That is, two cameras clip highlights at that ISO when exposed identically. This is not a standard definition of ISO.

All that means is that that if the difference between Dxomark's "measured" ISO vs the cameras stated ISO is larger (when measured ISO < stated ISO), that would mean that that camera has *more highlight DR*.

Check the DPreview (instead of dxomark) for A99's "measured" ISO ...

"The actual sensitivity of each indicated ISO is measured using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using a calibrated Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV (the margin of error given in the ISO specifications). We found that measured ISO from the Sony SLT-A99 is within +/- 1/6 EV of indicated ISO across its entire ISO range."

Now that's correctly "measured" ISO ...

Olympus PEN E-PL1 Sony SLT-A99
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