Originally smooth unicolor background shows "steps" in the color gradient when exporting I am using Abode Premiere Pro. 

I am working on a video which has a static background. The background is almost unicolor with a light color gradient. Please see here:



I want to export the video. The problem is that in the rendered video the background gradient is not smooth. The background shows "steps" in the color gradient. This is specially visible during fade in from a black screen/ fade out to a black screen. 

The "step effect" is stronger when I use a low quality or low bitrate output fromat. But even when I use very high quality output format the problem is still visible. And with very high quality I get a filesize of 13 gigabytes for a 15 minute video.

Here are some example settings wich gives a filesize of 1.5 GB. The "step effect" is quite visible.


1920x1080
length: 15 minutes 
25 fps 
H.264 
render at maximum depth 
bitrate encoding: VBR, 2 pass 
target bitrate: 15 Mbps 
maximum bitrate: 17 Mbps 
Use maximum render quqlity 
resulting file size: 1562 MB


How to solve this problem? How do I get a smooth output and acceptable file sizes? What is the best format, the best codec for this?
The choice of codec will largely depend on what you're doing with the material. Your problem is that there just aren't enough colours in 8-bit colour space to give you a smooth gradient over the size of the frame.

Problem is that if you want to deliver it on the internet you're pretty much locked in to h.264 (or I guess webm or ogv, but same deal). You can encode h.264 in 10 bit, but almost no-one will be able to watch it, and certainly not in a browser.

There is a workaround which can help a little, which is to add some noise to your gradient. What this does is to break up the banding so that it's not as obvious. It's called dithering, it was big when 256 colour gifs ruled the earth. See this answer for a bit more detail.