PHOTOS, ETC.

The Ratio Method


 
    The ratio method is based onthe mathematical verity that the original width is to the reproductionwidth as the original depth is to the reproduction depth. If the reproductiondepth is the unknown (as is most often the case), the formula is: 
 
(Reproduction Width ÷ Original Width)xOriginal Depth=Reproduction Depth
or 
(RW ÷ OW) x OD = RD 


Example A: ReducingThe Photo

    The original is a photograph 39 picas (61/2inches) wide by 48 picas (8 inches) deep. You want the reproduction widthto be 25.5 picas (that's 251/2 picas or 25p6). Youneed to calculate what the reproduction depth will be. The following assumesyou will proceed with a calculator. 

Step 1: Dividethe reproduction width by the original width.

25.5 ÷39 = 0.6538461 

Step 2: Leave0.6538461 on the calculator screen and multiply by the original depth tofind the reproduction depth. 

0.6538461 x 48 = 31.384615

    Thus, you  would indicate a depth of 31.4 picas(or apporoximately 51/4 inches) on the layout. 

Example B: EnlargingThe Photo

    The original is a photograph 27 picas wide by 16picas deep. You want the reproduction width to be 39 picas. 

Step 1: Dividethe reproduction width by the original width. Rememberthe formula is (RW ÷ OW) x OD = RD

39 ÷ 27 = 1.4444444 

Step 2: Leave1.4444444 on the calculator screen and multiply by the original depth tofind the reproduction depth. 

1.4444444 x 16 = 23.1111111

    Thus, you  would indicate a depth of 23.1 picas. 

    Warning:The potential danger is this method of calculation is forgetting to convertpica measurements to decimals. Remember, for instance, that the expression25p6 means 25 picas and 6 points. The 6 points, of course, are equal toone-half of a pica. So 25p6 should be entered in a calculator as 25.5 picas.Remember that 3 points equal .25 picas, 6 points equal .5 pica, 9 pointsequal .75 pica, etc. 


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