They're linked but that doesn't mean the light loss is due to the magnification.
Increased Distance = Magnifcation & Light Loss
You can't say that Increased Magnification = Light Loss because that simply isn't true. The same thing that causes the increase in magnification ALSO causes the light loss.
I have already explained this several times, but you could apply simple algebraic techniques to your equation and make any of the three items the principal of the equation! I was never trying to give a total explanation of the working of lenses, cameras, lasers, light etc etc just that there would be a loss equal to the square of the magnification! Just that.
Apart from anything else in order to calculate the light loss you need to know the distance of extension. If you wanted to calculate it from the amount of magnification you'd still have to work out the extension in order to use the inverse square law - which, as we all know by now, is based on DISTANCE
OR it can also be based on my calculation! ie 8x mag = 8x8 times light loss
If you allow people to believe that then they'll want to know how much light loss there is based on the magnification, ie.
Q: If I use a 25mm tube on a 50mm lens which gives me 0.5x magnification how much light loss will there be?
A: Approx. 1 stop.
Q: If I used 50mm of tubes on a 100mm lens which also gives me 0.5x magnification how much light loss will there be?
A: Approx 2 stops.
Q: Why is the light loss different if the magnification is the same?
A: Because it's the simple explanation... :bonk:
If we JUST look at magnification:
you have a macro tube on a 60mm lens giving a magnification of 8 then the light loss is 63/64ths.
you have a macro tube on a 105mm lens giving a magnification of 8 then the light loss is 63/64ths
(but these would be different tubes!)
I TOTALLY APPRECIATE WHAT YOU ARE SAYING (and you are not wrong either in your descriptions but...)!
I am not WRONG we could argue over which way of describing it is best and I would accept this quite happily. My explanation is sound for the example it was used for.
I have a high degree of understanding of physics but I wont pretend to say I am necessarily explaining it the best way - just the way that seems best to me! I was just trying to explain a simple thing using laymans terms without going into lots of detail and causing confusion! (which I think we have done now!)