Suppose I am shooting in low light with a 20 mp (compact) camera.
If I change the image size to say 5 mp, can I then use a faster shutter speed / smaller ISO setting?
In other words, is there a trade-off between the image size captured, and exposure? Here, four pixels on the sensor will gather light for each pixel on the image.
I have an old Canon A720 8 mp compact camera. When I fix the ISO and aperture settings, changing the image size does not change the (automatic) shutter speed. So it appears that there is a 1:1 correspondence between the sensor pixels and the image pixels. Is this the same with all cameras? Do they just crop the image?