Using a negative image instead of a positive image can be advantageous when
you want to focus viewer attention on the screen. Negative transparencies
are known as reversals. They have a clear image on a dark or colored
background. Reversals are easier on the eyes than positive images. To
prevent eyestrain, do not mix reversals with positive image viewgraphs.
Start with a negative image master or make your own negative by using a
commercially available reversing film in the diazo machine.
Figure 2-24 shows an example reversal.
Figure 2-24. A reversal.
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