D3 sensor efficiency

Started Nov 18, 2007 | Discussions thread
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ejmartin Veteran Member • Posts: 6,274
D3 sensor efficiency

As a companion to the dynamic range measurement reported here:
http://forums.dpreview.com/forums/read.asp?forum=1021&message=25627719

I have now also measured the (full well) capacity of the pixels of the Nikon D3. I found that at the base ISO of 200, the full well capacity is 53,400 electrons, a new high among DSLR's. The previous record holder was the Canon 1Dmk3, whose well capacity at ISO 200 is about 39,500.

To put this in perspective, if we scale up the 7.2 micron photosites of the 1Dmk3 to the size 8.46 microns of the D3 photosites, the scaled up photosites would have 54,600 electrons full well -- the same within experimental error. It seems then that the D3 and the 1D mark 3 have about the same level of sensor technology, just different choices for sensor size and pixel pitch. The read noises are comparable too: I found 4.9 14-bit raw levels of read noise at ISO 200, 14.3 at ISO 1600, and 23.3 at ISO 3200 for the D3; and for the 1Dmk3, 4.9 @ISO200, 12.1@ISO1600, and 23.8@ISO3200.

So it looks as though the D3 will indeed be the high ISO champion, by about .2 stop per pixel in midtones and highlights (and marginally even better as a percentage of image area due to having 20% more pixels, pushing the noise to finer spatial scales where it is less noticeable); the above figures tell us the relative photon noise levels when viewed at 100% (at the pixel level) are essentially the same as the ratio of pixel pitches. In shadows, the read noise dominates and the performances of the two cameras are roughly the same.

Note that my analysis was carried out on the raw files themselves, prior to raw conversion that adds additional uncontrolled effects to the image. The pixel capacity is a property of the sensor itself. A lot of high ISO samples from the D3 are jpegs exhibiting strong noise reduction (especially chroma noise); the direct analysis of the raw files renders that issue moot.
--
emil
--

http://theory.uchicago.edu/~ejm/pix/20d/

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