Using an Enlarger Meter?

[ic-racer]

The correction factor is different for every magnification, unless the meter got thinner as you move the enlarger head down.

 

[eli griggs]

Would no the Inverse Square apply as you lower and raise the head above the easel, with other factors of F stop, filters and time being separate calculations, AFTER the physical distance of lens head to easel, is accounted for in percentage of light as intensified or reduced?

 

[albada]

Would no the Inverse Square apply as you lower and raise the head above the easel, with other factors of F stop, filters and time being separate calculations, AFTER the physical distance of lens head to easel, is accounted for in percentage of light as intensified or reduced?

Here's the formula: L = 2*log2 (H/(H-M))
L = light-loss, in stops. That is, the meter's reported light-level is L stops higher than what the paper receives.
H = height of lens above paper.
M = height of meter's sensor above paper.

The multiplication by 2 comes from the inverse square law.
Here's a typical example using a 50mm lens for 35mm film: H=14 inches, M=0.9 inches,
L = 2*log2(14/(14-0.9)) = 0.19 stops

 

[eli griggs]

Cheers, it's always good to have and know how to make these calculations.

I generally print by eye, after starting out with a meter reading, but being able to take a known good final exposure, say for a 11 x14in. print and to be able to precisely scale up or down is invaluable in the darkroom and production of prints you may want to sell, at different price points.