Offering Potential Help with PEI Exercise
So, I studied The Negative, Zone VI workshop, Steve Simmons Work, and many other articles. I've having a hard time quantifying the precise relationship between aperture, shutter speed and film speed. The challenge posed itself when I wanted to take exposure in twenty-five or thirty percent increments.
Anywho, I built a model in Excel that can begin with calculating luminance based on 18% and Sekonic constant and then allows you to keep aperture or shutter speed constant and increase exposure by any increment value and then give you computed film speed.
Changing aperture was trickier becasue actual aperture size is dependent on actual lens length so, there's a variable for that too.
I'm wondering if someone is willing to check this over for me to see if it's accurate and makes sense. Once I get it checked over, I'd like to clean it up, include some notes and sources for the equations and make available to anyone who'd like to use it.
Is there anyone willing to help? I'll mail you the spreadsheet. Thanx