The amount of light from change in AOV depends on the scene illumination. For example there may be point sources or only part of the scene illuminated in which case the amount of light would remain the same or close to the same from a change in AOV.If the (absolute) focal length is the same, on Micro Four Thirds (µ4/3) the angle is narrower, meaning that less light is gathered.Yes, I guess he is right, but how does a f1.8 lens on mft = f3.6 in regards to light. If the focal length is the same then an mft 1.8 lens is faster then a f3.6 lens is it not.
50mm f/3.6 on µ4/3 collects only about 25% of the light than 50mm f/3.6 on a FF sensor because the angle of view is smaller. In order to get the same angle of view, the µ4/3 lens needs to be 25mm. In order to collect the same amount of light, the absolute size of the aperture must remain the same.
Aperture is: focal length/aperture diameter.
What this means is that 25mm f/1.8 on µ4/3 is equivalent to 50mm f/3.6 on full frame.
- 50mm f/3.6 has an aperture of about 56mm.
- 25mm f/3.6 has an aperture of about 28mm.
- 25mm on µ4/3 has the same angle of view as 50mm on FF
- 25mm lens with 56mm aperture is a f/1.8 lens.
This is a bit different when you change the focal length of the lens to the same AOV, in which case those variables can largely be ignored.
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