Student or Learner
http://www.rosco.com/us/technotes/designer/data_sm.cfmDoes this sentence sound strange without away?
Most heat sources should be kept about five inches (12 cm) away from the film.
No, in fact it is still perfectly understood and means the same.
However, the "away" emphasizes the message.
The "most heat sources" is very vague.
I'd prefer stronger worded instructions: Keep the film at least 12 cms away from any heat source.