of negative density; for this particular printing material on the Kel-O-Wat printer, 
for instance, 1076 CT at D,,, — 0.3 D means that the “effective gradation” for the 
low frequency range is 10% of the printing material’s gradation. 
For the photographie practice, the integral representation of this last point (4) in a 
modified H & D diagram shows two more important aspects: 
5. The point where dodging starts (figure 4); at a certain setting of the dodging print- 
er, the ordinate of this point - for D  ~ 0.2 D - determines for each particular 
positive material the proper exposure time, independent of the negative properties, its 
absciss - only dependent on the positive material’s transmittance - giving the upper 
limit of the reproduced negative density range. 
The ratio between the megative's original density range and the apparent density 
range; (figure 3) it allows the proper choice of the printing material’s gradation. 
This ratio is highly dependent on the mean negative density, on the positive material’s 
transmittance and on over- or under-exposure (figure 4). 
The above description of “dodging” in terms of “Contrast Transfer plus Density” is 
the most adequate one for this particular phenomenon, because it is an explanation 
based on the combination “Contrast Transfer plus Energy”. 
The dodging procedure is a typical example of an element in the image-forming 
system which cannot be described in terms of Resolution; only when using the Contrast 
Transfer theory it becomes possible to evaluate the performance of dodging printers. 
SUMMARY. 
A description of dodging printers’ performance is given on a combined “Contrast 
Transfer plus Energy” base. Results of measurements are shown. 
, , 
RESUME. 
On donne une description du principe ,,dodging" basée sur des notions de ,trans- 
mission du contraste et de l'énergie". Vous y trouvez les résultats des mesures. 
ZUSAMMENFASSUNG. 
Eine Beschreibung von Kontraststeuerung in Kopiermaschinen wird gegeben auf 
Grund von , Kontrastübertragung und Energie"-Erwáügungen. Experimentelle Ergeb- 
nisse werden gezeigt.