>>4170163This is wrong! The F number is indeed the ratio between the focal lenght and the entrance pupil diameter.
Yes, a f1.2 collect 4 time the light in respect to a 2.4. It's also true that an FF lense project light on a larger area than aps-c or m43.
BUT because you are keeping the focal lenght the same, FF lenses are just designed to project a larger circle on the focal plane! FF lenses always collect more light, but just to cover more area. The "flux density" is the same at a given focal length and aperture.
You can try it yourself comparing an aps-c and a FF lenses, same camera same parameters, etc.
>>4170174This is correct, but it applies only comparing sensors with the same resolutio.
It's also true that if you have a higher resolution FF and you scale to match a lower aps-c resolution you gain in sharpens.
Anyway, current sharpness/resolution is more than enough for most applications even in aps-c.
>>4170212This is complicated because FF lenses are higher quality and price by design because they target a different market than aps-c.
