How do you choose the right edge feathering technique for rotoscope?

Don’t do any edge feathering in roto. Certainly don’t export that matte out either. Let us unpremult the edge and control the masked transparency in comp. Giving me a feathered edge usually means what is behind the thing being roto’d gets brought into the mask. I’d rather have a hard edge that’s even - umpremult/blur/premult in comp with a control erode

I agree with Michael Callahan. Think of what will be considered in comp: Depth of Field and Motion Blur (camera and objects/actors). That should give you a better idea of why no edge blurs. You simply do not have the context to create them.

From recent experience, an article on creating proper basic roto would be a needed first step before the addition of fethering edges.

When QCing roto, I see artists use feathering to hide imperfections in the intitial roto in attempts to short cut supplying proper roto. Feathering is also used all too often in attempts to match motion blur when splines are being created every 1-3 frames, turning off shapes before properly positioning them in following key frames compared to properly using major motion keyframes and/or tracking.

To control the feathering of an edge, we need a matte. If the image we are compositing doesn't have a matte then we will need to create one. The two options are: A) keying B) roto If the image has enough contrast via luminance or color, then you can use keying to get a matte. This key may capture the fall off of the motion blur or defocus. If the key does not capture the edge, then we need to roto the edge. Every roto spline in VFX software can give you an 2nd spline for feathering. However I don't recommend this due to slower performance and the result will be a fixed option for motion blur. The recommended method for roto'ing motion blur is to roto a set of shapes and animate it consistently. For defocus, this can be applied after.

After an edge matte is created, a compositor would need to customize the motion blurred or defocused edge to the specific background content. And the factors mentioned above are the dimensions a Compositor would need to match the plate's characteristics.

When QCing, I see more effort in unsuccessful and rushed efforts to add feathering to edges that is then being rendered out as mattes, compared to more effort being applied to initial spline & script creation. Due to this methodology, roto becomes harder and more time consuming to fix later in the process by artists not creating the intial roto with less time to attempt last minute fixes. In comparison, AI roto being generated falls short in the same way as it is highly uneditable as a final product.

When it comes to edges mattes, I break the process into two steps: 1- Creation of a consistent hard roto done by a roto artist 2- Edge treatment and integration done by a compositor. The roto artist's goal is to create the most detailed and consistent roto possible. The compositor's goal should be to create a convincing comp, which includes creating convincing edges.

Are artists still using After Effects to create roto? A reference to Silhouette would be more aligned with roto software being predominantly used world wide today.