sensors, megapixels and such part1

Started 1 month ago | Questions thread
Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 15,329
Resolution etc.

Macro guy wrote:

So, here's my first question: Does having a camera with more megapixels provide any advantages if the final output is relatively small? For example, will a 50mp or 100mp camera show any practical improvement in image quality if the final print is 16x20? Is there an improvement in tone and color gradation? Anything that's noticeable?

Let me change your question a bit. Printers vary greatly in capabilities, and so it might be clearer if instead we compare the images on a good quality 4K monitor, one large enough so you can comfortably get close enough to see all available detail.

4K monitors are 3840x2160 pixels, making them somewhat larger than eight megabytes. But there are a number of reasons why more than eight can deliver better image quality.

These monitors have an aspect ratio of 16:9, making them more oblong than typical sensor formats, and so some pixels are necessarily going to be cropped away, and so you may need about ten megapixels. Cropability is a great reason for high megapixels anyway.

Lens corrections strongly benefit from increased megapixels, as these operations reduce resolution. Barrel or pincushion correction, perspective correction, transverse chromatic aberration, and diffraction sharpening all benefit from higher resolution.

Downsampling a high megapixel image to a lower value does not have to give you the same results as using a low megapixel camera to begin with, and some algorithms can give sharper-looking images.

Bayer filter cameras don’t deliver full resolution images. An eight megapixel camera only delivers four megapixels in the green color channel, and two megapixels each in the red and blue channels. So in order to get full color resolution at each pixel you’ll need more than four times the megapixels. 
So you’d need at least 40 megapixels to correct for the Bayer filter and cropping for the 4K aspect ratio.

But if you use lousy optics, terrible technique, heavy-handed post processing, etc., more megapixels won’t help.

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