Douglas Brown, a former classmate of mine, taught me how to batch process files in Photoshop. I honestly can't remember if he taught me this trick as well or if I came up with it on my own. Either way, thanks be unto Doug.
Open up the first frame of your sequence. In the actions window (if the window isn't there, just select it from the Winows menu bar) click the 'New Action' button (circled in red below). This activates a macro recorder.
From there use the magic wand to select the black area of the plate. I usually set the tolerance to zero, but you can adjust the tolerance if you have a particularly gaseous or otherwise mixed transparency explosion. Adjust the tolerance at your own risk though, as a zero tolerance selection is the safest bet. After you do the first selection for the black, go to the Select menu and choose select similar. Next, invert the selection (ctl+shift+I) then fill the new selection with white. After that, be sure to Save As! The name of the file isn't important because the batch process itself will use the original filename or you can choose to serialize the images. Last thing you do is back at the actions window. Click on the red block to stop the recording.
Now, for the batch process itself:
Close any files you have open in PS. Go to File->Automate->Batch and a new window will pop up.
It is pretty self explanatory. Choose whatever you named your action from the Action dropdown. Choose the source folder and a different destination folder as the batch process defaults to using the original file name. Leave the Save As Override unchecked, it turns off the save as feature. It's an Adobe thing. We wouldn't understand. Anyway, then press ok. Depending on how many files are in the plate sequence and the speed of your computer, you may have time to go get some lunch or something.
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