Banding is a distance, not a shade count.

A step in a gradient is visible because of how many pixels wide it is, and that is one division: the extent divided by the code values the gradient occupies. A sky over 1920 px occupying 20 code values steps every 96 pixels — a band you can point at. So “8-bit banding” is not a property of 8 bit. It is a property of 8 bit and how far the gradient spreads, and only one of those two numbers is usually in the conversation.

The engine is free and needs no account. A step needs to be both wide and tall to be seen, and those two are decided in different places. The width was fixed at the moment of quantisation: a grade cannot add levels, it maps every code to a new one, so the count of distinct values — and the step width with it — is exactly what the capture decided. What a slope of three does is make each step three code values tall, taking it from 0.392% of full scale to 1.176% and over the threshold. The grade does not create the bands; it raises the ones already there. They were at their full 96-pixel spacing the whole time. The page also works out what another two bits would buy, why conforming into a deeper container buys nothing, and what dither actually trades. Every lane ships a worked example that costs nothing. Writing the report needs credits.