is probably in the region of 1.?> and this figure has been 
taken as the basis of column 4* The use of soft materials 
has been advocated by a number of people, but they are not 
widely used. 
TABLE I 
1 
2 
3 
4 
T lores 
Representative 
Negative detail 
Density 
Ranges 
Enlargement from 
Printing G-amma 
$ Loss of Range 
between Print 
Cut Offs 
Bap er 
Range 
0.9 
Diapositives 
Range 1*7• 
0.8 
Soft grade x 1.6 = 1.3 
No loss 
Medium grade x 2.0 =1.6 
44/o 
No loss 
Contrasty grade x 3»0=2<>4 
62$ 
30% 
1.2 
Soft grade x 1.6 =1.9 
535» 
11$ 
Medium grade x 2.0 =2.4 
6.2$ 
30% 
Contrasty grade x 3*0 = 3«6 
75« 
53% 
1.6 
Soft grade x 1.6 = 2.6 
65% 
35% 
Medium grade x 2.0 = 3 «2 
72$ 
b-7% 
Contrasty grade x 3»0=4*B 
00 
-k. 
65% 
The effect of unsharp marking or electronic printing 
is to shade back the large areas of low negative density, 
and so contract the overall negative range to bring it within 
the scope of a medium, or contrasty printing material. In 
the open field areas one can by this means recover the losses 
of Table I, (though not necessarily at the full resolution of 
the negative). In view of the very large losses indicated 
in Table I it is not difficult to understand why the first 
demonstrations of unsharp masking created a major sensation. 
It must however be emphasised that the recovery of negative 
detail by these processes is literally confined to open 
field areas. This is because there is a practical limit to 
the size of detail that can be dodged. If the dodging is 
differentiated right down to the finest details, then from 
theoretical considerations one might expect the complete loss 
of fine detail in a general uniform density. In practice 
one obtains a heavy outlining of all large detail, in which 
phenomenon all fine detail disappears. The effect is thus 
the same, and to avoid it the dodging has to be confined to 
large areas. This is the reason why the mask must be 
unsharp and the flying spot of finite size.