First of all, I hoped I'm not asking a duplicate of some question (I didn't find any).
I'm currently editing a short-movie, and the main part of it is black and white. We recorded it in colors, so I'm using the video sequence editor to go in black and white for these sequences. My problem comes here (I'm setting the saturation of each strips to 0, but I tried other ways like using a Hue correction Modifier, same result).
Then in a scene, we used a old-look iris effect (darkening borders of the video). I tried different ways but all with the same ugly result : use a transparent png image, use a mask, ...). Here is the actual mask I'm using :
I can't see how to get it more simple than that. Then here is a zoom on a corner when I render a frame to a png image :
It looks normal, isn't it ? Let's see how it looks when I render the video in a .mp4 file :
It's a bit subtle, but I assure you it's reeeeeeally ugly. It looks like now Blender has only 10 choices of gray for that gradient. Shouldn't it have thousands or millions of colors available ? Finally, here is my configuration :
I want to underline the fact that I used the VSE for almost 10 short movies now, and the encoding has always been perfect. I always used H264 in mp4 container, and it looks great (lossless, any encoding speed). But that's the first time we are doing some part of a movie in black and white, and I'm really upset about this result.
Have you any guess why it's sooo ugly when rendered in a video ? What causes the loss of quality ? I have other small quality problems about black and white, but this one is really bothering me ...
Feel free to ask any additionnal informations ! And thanks a lot to have taken the time to read me !
NB : Our camera is a Sony A6000 (hybrid camera) and works perfectly.