Sekonic L-398 is 1 stop off..
I just got a second hand Sekonic L-398 (as a back up meter, since it does not batteries).
Checking it against my other meters (a Gossen Luna Six Pro 6 and another smaller Gossen) and it seems to be 1 stop off (less sensitive) consistently (have to check taht further. This is in incident mode, reflective mode is less clear, but I am most interested in incident metering for this particular meter anyway.
Not a big deal, one can adjust by dialing in say 50 ASA instead of the needed 100 ASA
So do these big selenium cells get less light sensitive over time?