Why is the "white to brown & white to blue" gradient generally considered a shiny metal?
What is the reasoning/theory behind this? Why those colours? (If someone says chrome, you might first think of shiny silver & gray — not brown & blue!)
Where was it first used to depict metal?
(Bonus: could it be succesfully used without the metal/chrome association?)
Image shows how Photoshop thinks the "chrome" gradient is oriented by default.
That image can go either way, but I would say it is upside down to understand the context of the name.
Essentially, "chrome" in its classic context really doesn't have a color—it's a mirrored finish on metal parts—and it can only reflect the environment it is in. Think desert horizon on an antique car fender, like a '57 Chevy, and there's your "metallic chrome".
The one thing that I always found fault with that gradient is the fact that the white part of the two sub-gradients is they both go in the same direction when they should go towards each other. The white is a representation of haze in the air, which increases towards the horizon. In the default, the haze is increasing towards the background in the sky but in the foreground in the ground.
Chrome has no color, just as a mirror has no color; it's all specular reflection. The colors in that gradient, then, are completely arbitrary.
What gives the illusion of a specular reflection as opposed to diffused (such as from brushed chrome or any non-glossy surface) is the hard edge on color transitions or highlights/shadows. If the highlight edges on the image below were blurred, the illusion would change from a polished surface to a matte.
Photoshop's chrome gradient attempts the hard edge, not terribly successfully imo, but without any other detail it really can't sell the illusion of a shiny metal. That kind of hard edge lends itself to vectors more than rasters, which is why Illustrator is actually a better tool (other than actual 3D rendering tools) for building "glossy" textures.
It is the basic reflection from the sky and earth reflected in metal. It was mostly used for car chrome illustrations from the 50's-80's.I believe it is upside down however.
