Quote Originally Posted by pluto View Post

just bought, but I'm not able to use it.
Is there someone that could kindly explain me how?

Thanks for ever,
One way here.

To get a baseline start with a negative that you have already printed well.

Set up the timer and enlarger exactly as you would to reprint that negative; height, f stop, everything.

Measure and note the setting for a specific tone, like black. You can use other tones like skin too.

Now you have 2 of the 3 major variables defined, a baseline for print time and paper sensitivity. The aperture is the wild card.

When you switch negatives or change enlarger height you measure the same tone, say black point, with the EM10 set at the number you measured above and then adjust aperture until you get green. That new aperture at the "old" time and "old" EM10 setting should put your new print close.

It is paper specific so if you change paper you need to set a new baseline. Contrast also plays a role.