dupe negative

Also, the final dupe negative was a "third generation" copy, and film loses quality each time it is copied.

The strange coloring and negative-image effects in these shots were achieved by the use of different color filters in the process of making dupe negatives.

Most of the effects shots in his earliest films were created via Harryhausen's careful frame-by-frame control of the lighting of both the set and the projector dramatically reduced much of degradation common in the use of back-projection or the creation of dupe negatives via the use of an optical printer.