Norwood's dome on incident light exposure meters

[Doug Kerr]

For many years, almost all incident light exposure meters (or dual mode exposure meters in the incident-light mode) have had a translucent dome-like "receptor" over the light sensor proper. It is generally said that this is to make the meter respond "appropriately" to the various components of the ambient illumination that arrive from different directions. But what does that mean, and why is this advantageous in making metered exposure determinations on an incident light basis?

The story behind this is fascinating (perhaps even shocking) on several fronts. I discuss this at length in my article "Norwood’s dome: a revolution in incident-light photographic exposure metering", which is indexed on The Pumpkin here:

http://dougkerr.net/Pumpkin/index.htm#NorwoodsDome

Best regards,

Doug