This is because Unreal Engine allows you to edit in linear space, but most computer monitors are set to correct to gamma space. Basically, in order for a medium grayscale value to appear on a monitor, you only need a small amount of light. Then the brighter you want the monitor, the more difficult it becomes to show brighter values. Around 0.2 is the real value for a medium gray. Most monitors use the sRGB gamma space which raises all colors to a power of approximately 2.21. This becomes especially critical when you’re designing very dark materials or linear gradients.
Textures will import with sRGB checked on so they should appear with the correct gamma. But if you generate a gradient in the engine, you need to gamma-correct it manually, either by raising it to a power of 2.21, or for a cheaper alternative, multiplying it by itself/raising to a power of 2, which uses far less instructions.
Haha, this was actually a significant problem for me! I released a shader to the marketplace that didn’t perform the right gamma correction, and the video was all wrong. Didn’t figure this out until the last second! Whoops! It’s not just a newb mistake, a lot of people don’t know this.