Film File Sizes - why is one bigger than the other?

Pupose: Sometimes customers ask why one file size is bigger than the other with regards to film transfer file sizes and different fps.  Here's an answer/explanation that may help.


As for the file size, that all has to do with the fps and the corresponding pull-down that is applied to the file based on the fps selected.  Basically, standard video is at 30fps (29.97) and this is the file that we are seeing.  Now depending on the fps selected, the video will have multiples of the film frame in the final file.  For example, if the file is processed at 10fps there will be 3 copies of each frame, if at 15fps there will be 2 copies of each frame, and at 30fps there will only be one copy of each frame.  16fps, 18fps, and 24fps do not evenly go into 30fps so they will be further complicated by adding pull-down frames to pad them to 30fps.  Therefore, in summary, a 16fps speed file will be larger than a 24P file just due to the number of frames.

I hope that I’ve explained it clearly enough….I know it took me a while to understand it at first.


Further info can be found in a document:  User Data\TMM\Research\16mm transfer units\Film Transfer process.docx