No...no...no. That's not what f-stop means.
It's the ratio between the focal length of the lens and the cross-sectional area of the opening in the lens. For a given lens opening, if you double the focal length, you double the f-stop number. For a given focal length if you double the diameter of the opening, you quarter the f-stop number (because you quadruple the cross-sectional area).
So a very, very short f1.8 like the iPhone lets in much, much less light than a 50mm f1.8 prime lens would.
Then again, the light a 50mm f1.8 gathers focused down to the size of the iPhone sensor would burn the sensor like ants under a magnifying glass. And to gather the same amount of light would require the same diameter of the lens furthest from the sensor (basic physics). So what you said utterly fails the common sense test.
First I think you meant that the f-stop is the FOCAL LENGTH / APERTURE DIAMETER
2nd. I'm just responding to someone who was comparing the f1.8 iPhone sensor to a nifty fifty.
All I wanted to say was that the only thing in common was the light intensity hitting the sensor. The same number of photons per unit area. That's all I was saying. Just like a micro 4/3 f1.4 has the same light intensity hitting its sensor compared to a Full frame f1.4.
I'm not saying the TOTAL light gathered by a 50mm f1.8 is the same on the iphones f1.8. Yes, that amount of light would probably kill the sensor.
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