Quote Originally Posted by litody View Post
yes but that is purely theoretical unless backed up with accurate calibration. Now lets see if you can tell him how to accurately calibrate his enlarger Y+M settings to get even spacing between grade changes and with a fixed speed point. These are things that ilford filters do out of the box.
And a 1/4 grade change is easily obtainable by altering developer strength if you really need to.
Who peed in your cornflakes and why are you taking it out on me? You'd have to do as much testing to accurately, repeatably yield that quarter stop with altering developer strength, which would never be as consistent as changing the filtration, because as developers get used and as they age, the impact of altering dilution changes. And as far as changing filtration is concerned, if grade 3 is 50M, grade 3.5 is 75M and grade 4 is 120M, then you can derive a reasonable working approximation of grade 3 1/4 from the logarithmic scale. It ain't rocket science, it's simple math. But in the long run, what does it matter that it's precisely grade 3 1/4? If you need more contrast than grade 3, and less than 3.5, dial in 60M (using my above hypothetical example), and if you don't like that, tweak it up or down a few CCs. Unlike color printing, a tweak in filtration finer than a quarter grade isn't going to yield a discernable difference anyway. Maybe your densitometer can tell the difference, but it's highly unlikely that your eye will.