question about scaling and specular reflection

[Vay]

i read about scaling a plane for drawing in ANdrew Loomis' book but i want to know if there is anything else in the book that is incorrect by today's standards.
Because a while ago i read somewhere that the shading in relation to where the light is is wrong in the sketches in loomis's book.

And i want to verify if method of scaling is correct in Loomis' book (though i am convinced it should be correct)

also is there a method for finding out where the brightest part of something is?
for example: an aluminum can being shine upon by in door light bulb. I can see all shorts of distorted bright spots and a specular reflection of the tab of the aluminum can (can containing consumable liquid with tab on top). And the letters on top are partly lighted such as HI ME 5c or CACRV of which are imprinted on the top.

also, when scaling does the scale have to be smaller as it get higher in elevation?

also can any1 recommend books on scaling?

[Flake]

This is one of those situations where you want to just get a can and look at the light on it...