Hi there,
Figure aperture to light like you might a dam full of water- (the light source), and a hole in the bottom of a weir (the aperture), thus, the bigger the hole, the larger the flow of water out of it. I know that doesn't answer your query sorry.
Or perhaps, electricity supply and an appliances draw on it, if you'd rather.
Also apertures effect can be diluted by a FL, but the effect is far from linear or standard, or practical sometimes for loads of reasons.
Rough analogies, but things are rarely absolute or black and white, especially when dealing with the EM spectrum, where nothing is ever wasted or used, just converted into another form of energy. The laws of optics are only clear and simple if you like to order your mind with absolutes, for your own convenience. Truth is the many variables behind optical performance would be near endless is you stopped to consider all the interactions.
Years ago I had to do some of this with math for imaging optimising in post-grad Uni astro studies for our optical trains, it was a real eye-opener, and a pain.
If optical physics prompts you to ask more questions than it does answer them, than you are on a track to truth, which is a pandora's box to say the least.
As for us hobby imagers, if it does the job and we get satisfaction from our efforts, then it is good enough and worthwhile imVho
Cheers and all the best.
