Originally posted by Ira Can I put this is dummy terms, Lowell? And tell me if I'm correctly explaining this?
Yeah, you can take the picture, even if it means hand-holding it for 10 seconds, but there's not enough light for the meter to operate and either do it for you in an auto mode or allow you to meter it manually.
In other words, your camera in a pitch-black closet can indeed take a picture of that old Nehru jacket--that requires lets say a 20-minute exposure--but the darkness is outside of the meter's sensitivity range to TELL you that you need 20 minutes.
Ira, the light meter reads a level of light coming through the lens. Let's imagine this level has a range EV0 through EV22.
EV 0 corresponds probably to something like a cloudy moonlit night.. This is the bottom limit of the metering range, and as a result, any light level below EV0 will be interpreted by the meter as < EV0.
The camera will only give you the equivelent aperture and shutter speeds possible (for the ISO you have selected) to match EV0, and the indications flash because the level is too low to accurately predict your exposure.
Depending on how you program your green button, this will change shutter, aperture or both, but will always tru to set it for EV0. If your setup restricts reaching EV0 the indication will flash. For example, let's assume you have a shutter speed set, and the green button function is to set aperture. If you (based on light conditions) need an F1.4 lens, but you have an F2 lens, the indications will flash because it is not possible to set the exposure within the range desired,
You may be able to also do this within the exposure range above EV0 if the combination of ISO, lens and shutter you have available make it impossible to set the exposure within the range the camera can control.