Originally posted by Gimbal In principle it shouldn’t matter if you up size or down size (or which size you aim for) since the comparison is relative. If it matters then there is something wrong with whole idea.
The original statement:
"Some sensors have more megapixels then other sensors of the same size"
"So what is the right ammount of megapixels to compare noise? Is it better to upscale or to downscale images to make them comparable?"
I believe it matters or it can in as much as apparent IQ changes due to what happens on several levels including the up/down sampling algorithms and what happens between cameras in the A/DC.
As an example 2 newish FF cameras compared @ ISO 3200 (same lens s/s and f/stop). One a 21 MP camera the other 47 MP camera:
First the 21 MP upsampled to the same size as the 47 MP. Noise is mushy as is apparent loss of resolution. Sharpening needed to bring closer and that sharpening will accentuate the noise
Second the 47 MP downsampled to match the 21 MP. Closer this time but still more resolution before added sharpening.
Bear in mind what you are looking at here is pixel peeping at 100% and the acid test would be to produce prints at the printers native resolution and judge from whatever viewing distance you imagine a print of yours would be seen at - it may or may not be noticeable and if it is then it may or may not be important to you
Last edited by TonyW; 01-16-2018 at 07:21 AM.