Ok so I will start with an example. Say I want a person in my shot to change an item they are holding in their hand from a cracker to a cookie or a knife into a marker. This effect would happen when the person concentrates and blinks.
I will explain how I think it can be done or how I would mentally go about doing this. I have only one day for the shoot I will be on and 2 days to create the successful effect so the footage I get will have to work. If you have a better/easier/more fluent way to do this (both during filming and in Post) please add any ideas you may have. It will be greatly appreciated.
Just to set this up the shot will be both a close up with the cracker near his head and a wide where him and another person are in frame.
I could shoot him holding the cracker then tell him to hold the pose and switch the cracker for the cookie and then just do a quick cut. While in my test shots this works it seems too noticeable of a cut.
2. I could shoot his face and then do the arm separate and mask in the arm with the cracker then replace the cookie, this way we see no cut in his expression or head movement and rather just the cracker/cookie. While this may work the hands may align perfectly. I could also direct him to do a slight hand movement so it almost looks like when a magician flips a jack into an ace extremely quick. (motion blur of movement may mask the cut)
3. I could also use a particle /puff to "hide" the transition of the cracker/cookie change.
4. The extremely long version which is motion track and insert a still image of the object into his hand then parent the picture of the object to the movement of his hand and just mask around the fingers so it looks as if he is actually holding it. This way I can freely change the items out with just the cut of a jpeg layer.
I know a lot of techniques but just feel as if I am missing That specific AhHa moment. Again any help would be appreciated and once I finish the effect (if I like the final result) I will make a tutorial and post the final shot as a reference.
You've covered the basics ways of doing this, if you are doing this on the cheap I'd do a combination of 2 and 3. Slight hand movement--separate the face and hand and a puff of smoke/lens flare...
Johnny Cuevas, Editor
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.