When film is developed to a
lower CI, for instance for use in condenser enalarger, it
must be developed less and the speed will be lower than that
give by the ISO test. For most film an adjustment to a one
paper grade lower contrast will require an increase in
exposure of about 3/4 to 1 stop. The difference in printing
contrast between a diffusion enlarger and a common partly
diffuse condenser enlarger is about one paper grade.

This puzzles me. I allways thought that condenser enlargers only
increase the contrast of the final print - nothing more, nothing less.
If we first decrease contrast (developing less, agitating less etc.)and
then increase the contrast back to normal using a condenser enlarger,
why would one have to expose at different EI? Shound't the decrease in
development negate the effect of using condenser and thus not call for
any change in EI?

Example, using diffusing enlarger, EI = (say) ISO/2 and we develop
"normally" and get:

Zone I at 0.10 above fb+f (so the used EI is "correct")
Zone X at 1.30 above fb+f

Let's assume that it prints very well. Let's also assume that condenser
enlarger increases contrast by a factor of 1.25.

So using condenser, EI = ISO/2 and we develop now a little less:

Zone I at 0.08 above fb+f (now the used EI seems to be too high)
Zone X at 1.04 above fb+f

Now using condenser the above "becomes" 0.10 and 1.30 above fb+f -
actually only the resulting densities at the print change but... So why
would I increase EI at the latter example? If I increase the EI to get
Zone I at 0.1, the result is that Zone I prints as 0.125 (1.25 x
(0.08+0.02)) and Zone X as 1.325 (1.25 x (1.04+0.02)). That would be
incorrect, right?

Regards,
Severi Salminen