it is said that full frame aperture equivalent of 2.8 to aps-c is 4.2. does it mean that shutter speed of aps-c is one stop slower that full frame on the same aperture? given the same focal length equivalent e.g. aps-c 23mm and ff 35mm.
it is said that full frame aperture equivalent of 2.8 to aps-c is 4.2. does it mean that shutter speed of aps-c is one stop slower that full frame on the same aperture? given the same focal length equivalent e.g. aps-c 23mm and ff 35mm.
But what is this “speed” or “fastness”? The f-number is not just some abstract unit, but it’s tied to physical reality.
To answer to that one needs to understand that this “fastness” refers to an exposure time (or shutter speed) one can use to achieve desired image quality. Thus f/2.8 on one format does not equal f/2.8 on another.
In principle f/4.2 on FF, f/2.8 on APS-C do an identical job - they give the same image quality (noisewise) with the same exposure time, the depth of field is the same and the blur from diffraction will be the same.