This is a strange little issue that has been brought to my attention by colleagues after they had some shots rejected in tech check (when they gamma slammed the heck out of the footage and saw these artifacts, ...when you know they are there, you can see them without any crunching of levels).
Basically when doing a scale up or down on a layer (more visible on the smaller scales) you get this grid-like interference pattern happening.
I have tried it on numerous packages. After Effects, Combustion, and Photoshop all had the same grid patterning when scaling up this 1080p footage by 104%. Nuke had it at its default cubic filtering, but could be eliminated by using Parzen or Notch). Shake was the only application that seemed to do the transforms without creating the grid interference (am guessing it uses a different transform filter by default).
Here is a link to the image (click on the lined thumbnail to see full image, I have marked little yellow squiggles at the start of the grid lines to help see them, plus the shot has been graded to make the grids obvious).
here goes
From what I can see it is something to do with After Effects (and the other apps) use of bicubic sampling. My questions are, has anyone else come across this, and if so, do you have a fix? My only suggestion to the others was an adjustment layer with a 1 pixel fast blur followed by an unsharp mask filter (at default settings), over the top of the worst clips. Not ideal as the image becomes slightly softer, but at least the grid is dealt to enough to be passable.
Its a real head scratcher as I have never encountered this before in AE, ...and it seems to depend on the footage, as other clips seem to scale with no artifacts.
Cheers,
andrew
