more pixels are better!

Started Dec 14, 2008 | Discussions thread
John Sheehy Forum Pro • Posts: 25,912
Re: To be more specific...

DaSigmaGuy wrote:

Everyone knows that downsizing an image hides image noise so its
hardly supprising your technique of downsizing the larger 50D image
to the size of the 40D image makes it look less noisy!...Your
technique is therefore completely flawed and the results therefore
irrelevant.

Downsizing an image with proper resampling does not "hide" noise. Unless the noise was periodic, and the new pixel size an integer multiple of the period, the noise is still there. It exists at a smaller depth, in a bigger pixel, with the same effective noise at all common image frequencies with the original.

Take any noise from a camera with low MP, and upsize it to the number of pixels of current high-MP cameras, and the noise becomes more intense at the same resulting-pixel magnification. That's because the real issue in the visibility of noise is the displayed magnification of the image. You don't need to downsample to "hide" noise. You simply have to display the image smaller. If you have to "hide" noise from a 15MP to match an 8MP, then simply displaying them at the same size would also give equal visible noise at common image frequencies, without any loss of resolution for the 15MP. Imagine that your monitor was 100MP instead of 1 or 2 MP, and you had to upsample all images to view them full-screen, and that 100% pixel zoom viewing had no special interest, except to make higher-MP images larger than lower-MP images, but none filling the screen very much. Then, we could truly say that the lower-MP is HIDING its noise by being displayed at a smaller size.

Displaying images small hides noise. Downsampling does not hide noise; it only hides resolution.

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John

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