Monday, 23 May 2016

Does noise in images depend upon "Megapixels" or "ISO"?


I have a question about image quality. Does noise in an image is depends upon "Megapixels" or on "ISO"?



Answer



Noise originates due to a number of factors, see:


What is noise in a digital photograph?



Increasing the number of megapixels keeping everything else constant (sensor size, technology etc.) will increase noise per pixel, but also has the effect of making the noise finer grained which is less objectionable.


ISO does not by itself increase noise, only if you combine increasing ISO with decreasing shutter time / closing aperture.


It's [probably] worth repeating this again here...


Increasing ISO whilst keeping shutter-speed/aperture constant does not increase noise:



Here is an example, as the ISO 100 shot was underexposed, raising the ISO to 1600 yielded a much less noisy result!


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