Quote Originally Posted by Photo Engineer View Post

How do the exposures compare for time and lens opening?

Here is a test and a method that I have been using, not sure it will answer your question.

I have a Sekonic L-358 light meter that I remove the dome from, Sekonic calls it a Lumisphere. It will detect much lower light levels this way. I keep it set at iso 100 and use it as a standard to gauge changes in light intensity.

I made a contact print with a bare bulb, just like I have been doing. The exposure is 5.6 sec. I measured the light falling on the printing frame at Ev 9.5. I then set up an enlarger to make a 4x5 print and at f11 obtained a reading of Ev 7.5. That;s a two stop difference, so 11 sec. @ f/11 should be an equivalent exposure. I made several test prints like this on a condenser and a color enlarger. The print from the condenser enlarger had more contrast than the color enlarger print.

Two scans: top, a contact print and bottom, from the condenser enlarger. I actually used 13 sec. @ f/11 for the enlarger produced print, but that's only a third of a stop.