Originally Posted by Waterman100
I was about 5 feet from the wall.
Light source was fluorescent light from the ceiling, and some natural light (bec window blinds were lowered) from the window.
Does this help?
So you were probably closer to the light as well
? Remember the inverse square law...
But the main point is that as Stephan says, you'd get the same reading with a grey mid-tone (ideally 14%, not 18, but the difference is not great).
I apologize for confusing matters earlier. Some meters have different indices for subects of different reflectivity (I'd just been writing about spot meters). With a very bright white wall under exactly the same illumination as the incident dome (same distance from the light), and using the same index, you'd expect a difference of about 2-1/2 stops (the wall reading brighter). With anything other than a very bright white wall under identical illumination, or a neutral grey card under the same illumination (where the readings should be very close), all bets are off.