The digital spec is well defined. In a 10 bit it is 16-255; 8 bit it is 16-235. On a projector with dynamic iris, a 16 black chart displayed in a blackout room has no light output. OLED should do the same. At the bright end of the spectrum, color and white can produce excellent spread without clipping to 2000 nits on OLED now. LCD/LED at best is 1000 nits. Projectors can reach to about 500 nits but these are rather expensive laser engines. A projector is a problem to figure the nit light off the screen because the screen can range in size, bigger screen area - lower brightness. Therefore the way projectors are compared is light output from the lens in lumins. 1800 lumins is about top for a UHP lamp at 280 watt. On a 100" diagonal screen with a 1.0 gain matte white is only about 150 nits. The same screen area, a 100" OLED is probably the best display for overall image, but if you want large screen, today, a projector is the way to go for $ cost but then HDR, especially, will suffer. Last I saw a 100" OLED was about $100,000. Equivalent size projector for 150 nits is about $10,000. In other words, pick your compromise.
The gradients to avoid color banding is a different spec. The Sony ( what I am familiar with) using SXRD panels has a "Triluminous®" engine that produces over 33,000 colors at once and can add sharpness to the picture without the traditional white edge artifact common to LED and super OLED screens.
