Yesterday I was in the Sloss furnaces just before a storm hit so was getting some nice light on the exterior. However I found an interior shot where the only light source was a window behind me and the subject was gray metal gears and rusted parts. The only thing I could measure with a spot meter was a bit of yellow sand on the floor and it was EV3 which is the lowest my spot meter can read apparently. From that I extrapolated the best lit metal would be 1.5-2 stops less, and did a best guess for exposure hoping that I have enough detail at Zone 3 with some expansion. I did not account for any bellows factor which is likely going to lead to under exposure. Final exposure f16 at 4 minutes.

I just now learned that my spot meter when switched to incident will measure down to -1EV. Would it have been more effective to use the incident (assuming it would have read a bit higher than -1)?

Also how do you focus in the dark? with f5.6 I barely could make out the item closest to the camera.

Has me thinking future purchases need to be f4-ish lenses for my commonly used lenses and a newer spot meter model with more sensitivity. I rarely shoot below average EV7 so not in a rush, but more of a nice to have.