A diagonal line drawn from corner to opposite corner will be the diagonal of a larger or smaller illustration made from that copy. Use a tissue overlay paper for drawing the diagonal.

A slide rule is also a useful device to determine the reduction of a photograph or drawing.

GRAPHIC PRESENTATION

A photograph which is to be printed or reproduced should never be rolled. If it is absolutely necessary, roll the photograph with the picture outside. Then if the surface should crack the cracks may close up when the photograph is flattened out.

Instructions written on a photograph or picture will often appear in the halftone. A paper clip often cracks the photograph and appears in the finished picture. Writing should never be put directly on a photograph or drawing. Instructions should be written on a separate piece of paper and folded over the margin.

Steel Industry

Wrong Way to Make Crop Marks. See 413 for remarks.

PREPARATION OF ILLUSTRATIONS

To determine whether a cut is already a halftone, look at it through a small magnifying glass. If the shaded portions appear as many dots, it is a halftone. Halftone screens are designated as fine or coarse, depending upon the number of lines of dots to the inch.

A rotogravure illustration when looked at through a small magnifying glass appears as many small squares, less clearly than a halftone.

Right Way to Make Crop Marks.

Put crop marks in the margin of a photograph or drawing. If you MUST mark the copy, use a China marking pencil for this purpose. The reason for this is simple:-- crop marks drawn on the photograph oblige the engraver to make the plate smaller than the size indicated by them.