LittleWolf said:Not necessary to thank me; helping the needy is only sound practice.
You could use a physical instrument like a light meter to make a measurement. You can relate this measurement to the sensitivity, which is defined by physical measurements as well (but the manufacturer should have done this for you already). You convert your findings to a combination of physical quantities such as (exposure) time and aperture.
The necessary basics of light were understood long before Nikon (a physical instrumentation company, by the way!) and Canon were even founded. And long, long before Ansel Adams cooked up his "zone system". But Ansel Adams was not rooted in science - he was a pianist - which might explain things to an extent.
Thank you indeed!
Such sound wisdom, and so clearly and succinctly expounded! We now understand fully what you are saying. I am sure all of us are indebted to your kind efforts to show us the light.
Now I have this silly spot meter. And I just pointed it at the white dress my friend is wearing, and it reads f8 speed 1/125. MY ISO is 400.
Now please enlighten me more in your so concise and succinct manner. Shall I set my shutter speed to 1/125 and f8?