Noise Reduction ... or Something Else?

Started 2 months ago | Discussions thread
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bclaff Veteran Member • Posts: 9,420
Noise Reduction ... or Something Else?

When I analyze raw files at PhotonsToPhotos one step is to produce 2 dimensional Fourier transforms (2DFTs) from the center portion of dark frames.

I admit I don't always look at every ISO but normally just for the boundary (if any) at high ISO settings where Noise Reduction (NR) begins.

These files are always collected with NR off (or if off is not an option to the lowest menu setting).

Here's a mosaic of the 2DFTs for a camera in whole stops from ISO 50 to ISO 819200:

Best view "original size"

These are displayed in ImageJ and heavily pushed to expose patterns.

It looks clear the NR start between ISO 102400 and ISO 204800.

There's a hint of something at low ISO; perhaps mild filtering for bad pixels?

That mosaic is for Electronic Shutter (ES); here's the one for Mechanical Shutter (MS):

Best viewed "original size"

Now something is clearly going on at low ISO settings, looks like ISO 50 to ISO 800.

Looks like NR to me but I'd like to hear alternate theories.

I'd also like to hear ideas on how to distinguish NR from other nearest neighbor processes like bad pixel filtering.

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Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

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