Chagall Reference   Densitometer           12.5.93
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   With the aid of the densitometer you have 
   the possibility of individually measuring 
   colour values in various regions of the picture.

   For this Chagall will show a dialog that will 
   display the colour values in the measuring 
   region on the basis of the selected colour-model.
   In the 'Min', 'Mid' and 'Max' columns you can
   read off the minimum, average and maximum saturation
   of the basic colours in the just-measured region.
   In addition the last line shows the intensity
   (brightness) independent of colour.
   
   To carry out a measurement select 'Activate'. With
   the mouse cursor, which will appear in the form
   of hollow cross-wires, you can now measure a given
   picture area by clicking on it with the mouse. 
   Chagall will then evaluate a square around the 
   measuring point whose size in pixels has been set 
   in 'Measur.range'.

   To quit the function click the right mouse button.

   The densitometer is suitable for establishing 
   colour values at individual picture points as 
   precisely as possible. The information obtained
   by this is useful, on one hand, if one later
   needs a comparable colour. On the other hand
   the values established with the densitometer 
   are suitable for estimating the printed appearance
   of a colour present in the picture with the aid of
   a colour-table (e.g. Euroscale, Munsell chart etc).
   It should also be mentioned here that the densitometer
   can of course be used also with monochrome pictures,
   where naturally only a measuring region encompassing
   more than one pixel has any meaning, since one is
   then measuring a density made up of dithered full black
   and full white pixels.
