OK, not sure what to call the effect. I do a lot of light painting, and typically just shoot long exposure stills. I want to achieve the same effect with video, mainly so I can analyze my technique and do some tutorials. So say I draw a pattern with a light - as the pattern is drawn, I want it to stay on screen.
I've tried a bunch of effects, but can't get what I want. I tried "echo", but the image winds up with a bunch of gray bars and loss of detail, plus it flickers. Echo was the best I've found so fat.