Updated: Feb 25
From the earliest days of variable density displays, there has been a question of which colors you should use for which polarity. Given a standard blue-white-red palette, the EAGE decided that red should represent an increase in impedance (positive numbers) and blue should represent a decrease (negative numbers). The SEG, on the other hand, decided on the opposite.
Given that there doesn't seem to be an inherent polarity to color, each option appears, at first glance, to be equally valid. If we consider seismic amplitude to be structure, which we always do in Stratiscape, then there is no reason to believe that red is structurally high and blue is structurally low, or the other way around.
But if that is the case, and there is no inherent polarity to color, how do you explain the two images in the slideshow below?
The only difference between the two is that the color palette is flipped. With white as structurally high the display appears normal. But when the palette is reversed and blue is high then you get a horrible optical illusion that makes the display almost impossible to work with.
Check out this video is from my introductory series on Stratiscape Scene Navigation. It discusses a new option that auto-flips the color palette as you go from looking at the front of a scene to looking at the back.
More than that, though, it discusses the polarity issue for seismic, arriving at the conclusion, albeit briefly, that color does indeed have a polarity. And you had better get it right or take Gravol.