Dpreview editor is a liar

On Wed, 22 Nov 2017 17:23:19 -0800 (PST), RichA
wrote:

This statement is B.S. Doesn't matter what noise ultimately looks like, sensors are sensors and lens speed is lens speed. He tries to qualify what he has by claiming the images are "very, very similar" but there is NO getting around the fact an if an image is shot on an APS and correctly exposed, and one shot on a FF with 1 stop under exposure, it is STILL underexposed. Arguably, you can make the images look similar by raising the illumination levels in the FF image afterward (because it has lower noise levels), but it is still not exposed correctly. This "equivalency" stuff just serves to make people even more ignorant about lens physics than they already are.

Richard Butler:

The F-number itself is unchanged. However its effect on an APS-C sensor is the same as ("equivalent to") using a 27mm lens with an F4.2 aperture on a full frame camera.

Mount an 18mm F2.8 lens on APS-C and a 27mm lens set to F4.2 on a full frame camera and the sensors both 'see' the same scene through the same sized hole. Oddly enough, expose them for the same time and you get very, very similar images.

It's not the same size hole if it is f/4.2 on both cameras. It is 1.5
times larger in the 27mm lens.

The standard exposure model obscures this relationship, in favour of making life simpler across formats. But what Barney has said is demonstrably true.
--

Regards,

Eric Stevens