>>4243372>They [f stop numbers] are derived from your lens' focal length divided by the diameter of your aperture. They represent a fraction of your aperture opening. For instance, an f-stop of f/4 means 1/4th or 25 percent of the lens is open. On a 100mm lens, f/4 would measure 25mm or about an inch.let's say we have a 50mm on FF and a 25mm on m43 (to achieve the same FOV).
50/2 = 25mm (a 25mm hole to let light in).
25/2 = 12.5mm (a 12.5mm hole to let light in).
you tell me that the number of photons which pass through a 12.5mm wide hole is the same as for a 25mm wide hole?
to have the same amount of light pass through both lenses the m43 lens would have to be a 50mm lens, too. but that lens would have a FOV of a 100mm lens on FF. which equals to a crop roughly half the size. so yeah, f/2 will pass the same amount of light but ONLY if the foal length is kept the same. if you play the focal length equivalence game then the amount of light needs to be adjusted too.
