[pEviLLE] SCREEN IN THE PHOTO-MECHANICAL PROCESS 61 
This method is unfortunately restricted to dry plates, otherwise it would 
be the best of the three. 
The cross-lined screen mentioned above is one in which the opaque 
and transparent lines are of equal width and has to be used with a 
double aperture diaphragm, but it must be remembered that in order 
to produce as good a result as the chess-board screen, the adjustments of 
the screen, plate, and diaphragm, would have to be three times more 
accurate and the screen itself three times more perfect. 
