A friend of mine and I had an argument about the brightness of the lens. I believe that lens brightness is primarily the amount of light passing through the lens and depends on the glass material. A friend of mine says there is no connection with the glass material and gives the formula from Wikipedia. I think that Wikipedia gives a simplified formula, since the degree of transparency of all glasses is approximately the same, and I am deeply convinced that the material of the glass should affect the brightness of the lens.
I ask you to speak out on this matter or send me to a more appropriate forum for this question.