From DXOMark: More pixels offsets noise3

Started May 30, 2009 | Discussions thread
ejmartin Veteran Member • Posts: 6,274
Re: Terms - not too confusing

natureman wrote:

Bogdan_M wrote:

These two things are the same. Image level for him was normalisation
(by downsampling with preblur) and then comparing the normalized
images at 100% (because once normalized they have the same

How can you consider that the same magnification? If one image is
downsampled (or upsampled), and the other is not, to match the sizes
of the images, the magnifications are not the same.

Two FF images, one 12MP and the other 24MP, start off their life both the same size -- 24mm x 36mm. When viewed at 100% on a monitor, the 24MP image is magnified by a factor sqrt[2] 1.4 times more than the 12MP image. By downsampling the 24MP image to 12MP, one restores equal magnification to both images (for the purpose of viewing at 100% on a monitor).

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