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10-09-2010, 04:38 AM   #31
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QuoteOriginally posted by Eruditass Quote
I meant equivalent to RAW. If RAW has that level of NR, that's ridiculous.
No one knows how much noise reduction is actually applied to RAW on any given camera. The K20 supposedly had some noise reduction applied even to RAW files starting at iso 1600, while the K7 allowed you to turn it off all the way up to iso 3200, but is off really off? People like Gordon B Good attempt to figure that out and feel like most companies apply some NR even to RAW files at high iso. This can be used to a certain extent to manipulate Dxo scores.

10-09-2010, 07:32 AM   #32
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There is NR and NR.

What is shown in the Sony chart mostly describes normal engineering. The analog noise reduction is interesting. But may be nothing but a higher gain in the charge-voltage conversion (with higher ISO) combined with some clipping. And the RAW NR done on chip may be hot pixel treatment and fixed pattern noise reduction which must always be applied to sensors. It may also involve binning of dark pixels which is where Sony seems to trick a bit. Or a weighted averaging of pixels beyond some ISO threshold like Pentax does.

Nevertheless, that's all playing kindergarden games. Real NR is a sophisticated algorithm based on information theory where the most likely signal prior to noise is reconstructed (it is clear that the original image is not the most likely signal because is has too many high spatial frequency terms). I've written one such algorithm myself. It's doable in the camera firmware but most in-camera implementations are poor, i.e., they reduce both, noise AND signal (IMHO, Nikon has the only fair in-camera implementation today). This is where RAW converters and NR software come into play. The JPG settings for NR almost only apply to this last stage of NR and "off" means a setting where the reduction of the signal isn't so obvious.
10-09-2010, 07:41 AM   #33

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This extra diagram may help clarify some of the NR processing in an Exmor sensor.

10-09-2010, 08:42 AM   #34
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QuoteOriginally posted by rawr Quote
This extra diagram may help clarify some of the NR processing in an Exmor sensor.
Thanks. The magic and new word in this diagram is CDS. It is used in conjunction with "noise cancelling" and "sampling system". Therefore, it is clear what they mean: Correlated Double Sampling.

This is common engineering practice indeed. It isn't noise reduction in photography terms. It's removal of an unwanted extra signal caused by non-linearities. It is more like a dark frame subtraction than conventional NR. To do this on-chip is perfect and won't take away from the signal.

10-11-2010, 04:29 PM   #35
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QuoteOriginally posted by Fl_Gulfer Quote
If you were all quiter when takeing pictures you wouldn't need all that noise reduction....
"Needing" NR doesn't equate "Discussing" NR !


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