Jack, 

The only reason targets are still included in the IPC-D-310, Guidelines for
Phototool Generation and Measurement Techniques, is for inspection of size
accuracy. Suppliers of phototools should have a quality assurance procedure
to verify accuracy of size. This may be an SPC program, or other acceptable
method. The receiver of the photo tools also needs a mechanism to verify size
accuracy. The targets provide a fixed feature for measuring this accuracy.
Targets are not necessary, if an alternate acceptable method is used. The
standard also recommends that temperature and humidity be marked on the plot,
so that verification of size can be acomplished under the same conditions the
film was plotted at.

Regards,

Gary Ferrari
Executive Director
IPC Designers Council

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