Density of negatives

Densitomètre à transmission
Densitomètre à transmission

Densitometric balance of films :

Ideally, the densitometric balance of negatives for collotype is situated in an interval of densities included between 1,00 and 1,20. It is nevertheless necessary to know that the concentration of the photosensibilisant, power of the UV source can make vary these indications. For example if we augment the quantity of making sensitive and what we use a powerful U.V. source, will be needed less contrasted negatives, otherwise to the edition it will be difficult to print an image balanced well – it shall be too much contrasted.
The best, to control the density of films, is to use a densitometer on transmission. To make this calculation, we subtract the value of the transparency measured in the clearest part in the value measured in the darkest part. The table below gives some examples of measures.

 
Darkest zone
Clearest zone
Density
Value
1,82
0,46
1,36
Too much contrasted
1,44
0,52
0,92
Lacking contrast
1,38
0,26
1,12
correct