[Frameworks] removing dust marks on transfer

[Dave Tetzlaff]

> I was thinking it would be an expensive process to remove digitally.

It's not necessarily _monetarily_ expensive. You can do it manually if you can afford the time. Of course, you want as clean a transfer as possible, but there are still likely to be some big nasty dust spot every X number of frames.

The trick to manual dust removal is that your spot is only on one frame while the image likely persists over several frames. 

1. So you put the film in a timeline in FCP or Premiere or whatever in two layered tracks. 

2. The top is the copy-to-be-repaired and the bottom os the "patch". 

3. Offset the bottom track/layer a couple frames in either direction.

4. Make a four-point garbage matte around the first dust spot, applying a lot of smoothing to the outline and a lot of feather to the edge.

5. Voila. The frame below should now fill in the dust spot.

6. Copy the matte, paste it into the other frames with dust spots, and move it over the spots. (This is easier than drawing a new matte). Frames with more than one spot need more than one matte.

7. Review each filled spot. Most will probably look OK as the part of the patch frame peeking through will be similar to the hole in the repaired frame. Where the camera or subject have moved enough, though, there will be no match and the patched hole will as obvious as the original spot. So we need to get a proper fill under the hole:

   A. Cut and trim the video in the patch track, so you can move this particular patch frame around without messing up any others.
   B. An appropriate fill area is likely to be available either in some other part of the patch frame, or a on a frame offset in the other direction - i.e. if your patch track is +2 frames offset from the main track, a frame at -1 offset might work. 
   C. To save time you'll prefer to do one or the other: 1) offset the XY center of the existing patch frame,  2) try a different patch frame a few frames away, but not both unless it's absolutely necessary.

8. of course, you only want to perform this operation on frames that are for sure going to be in the finished film, so it comes after you have a tight edit (but before you do any slo motion effects in software...)

...

Yes, I've done this for a half-hour film. Yes, it was incredibly tedious. Yes, it took a very long time. Yes, it took several passes because I kept finding spots I'd missed on the previous pass. Yes, the results were worth it. In this case anyway.

As Jeff noted I think only half-jokingly, a certain amount of imperfections can be part of a filmic aesthetic. It all depends on material and purpose. Sometimes you'll want a little dust, sometimes it won't matter, sometimes you need the frame to be really clean to preserve the fragile poetics of a shot. So when I say my labor was worth it, that's contextualized by how much clean-frame-vs.-dusty-frame mattered in terms of the aesthetics of the particular work at hand. YMMV.