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Re: [OM] High-ISO performance Rant - Saying it with pictures

Subject: Re: [OM] High-ISO performance Rant - Saying it with pictures
From: Moose <olymoose@xxxxxxxxx>
Date: Sat, 27 Dec 2008 22:26:59 -0800
Chuck Norcutt wrote:
> Well, you are correct at a certain level.  According to Canon's white paper 
> on the design points of the 5D is says: "Also significant are the large 
> microlens array that gathers light for the photodiodes with great efficiency 
> and the second-generation, on-chip, noise reduction circuit that effectively 
> minimizes random noise and eliminates fixed-pattern noise."   ...  I believe 
> that the on-chip noise reduction is something much different than the large 
> pattern noise reduction done by the likes of Noise Ninja, etc.  The large 
> scale software pattern analysis ultimately ends up mistaking some image 
> detail for noise and ends up softening the image.  I don't think that's 
> what's going on on-chip and that's why you don't see something that looks 
> "processed". 

Ctein put it succinctly on TOP a few days ago "A problem with sensor 
arrays is electron leakage between the pixels. All sensors suffer from 
this. It reduces low-light sensitivity, decreases sharpness, and 
degrades color rendition. A new design adds a secondary well layer 
beneath the pixels that insulates them."

My recollection of Canon's on-chip NR is that it is of this general 
variety, somehow capturing and consigning to a bit bucket straying 
quanta of charge that would otherwise likely find their way to another 
site. The details may be different, but the idea is the same, reducing 
inter photosite leakage.

Hard to blame them for doing it on RAW too, as it can only be done 
on-chip in a way that will improve any image, RAW or JPEG processed, and 
can't be turned off.

Like Chuck, I don't think it is NR in the sense you are talking about.


> Although that certainly happens in JPEGs.
> Chuck Norcutt
> Ken Norton wrote:
>> I beg to differ.  All DSLRs apply some form of noise reduction to the images 
>> prior to the RAW file being written.  Canon, in fact, is very clear about 
>> this as they apply substantial noise-reduction right within the CMOS and 
>> initial data processing.  The sensor, in Canon's case, is "profiled" as to 
>> the specific noise characteristics and this is taken into account during the 
>> initial bit-bending that goes on. Raw is not Raw.  

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