While Gaspar may have used 3 exposures, it was not necessary to do so. The 3 exposures with different times were used to balance the film to the light.

And, one thing that is missed is that since the dyes are in the film from the start, the film is totally black and thus is very very slow, even with coarse grained emulsions.

Thus, from the very start, DB materials were slow, sharp but very very grainy.