Ted Cousins
Member
Hi, Ted,
Ah, but to get that recommendation, we would have to feed the exposure meter an exposure index, normally expected as the ISO speed of the imaging system, however we have it "set". So how would we do that?
Got me there, Doug. All those orphaned L-398s (you have or had one, I think). I like mine, it says "ASA" on it.
No. It is that the so-called "well" is charged when the sensor is initialized, leading to an initial voltage on the well "electrode" (typically positive). Then each effectively captured photon annihilates one electron, leading to a progressive discharge of the "well", and a decrease of its (absolute) voltage.
Major oops on my part. I've seen the 3T circuit many times and never realized the significance of where the reset FET is !! Ah cain't hardly believe it.
So the photo-diode capacitance is charged on reset and discharged by electron/hole flow in the depletion region, if I understand correctly. That makes the term "well full" and those pretty pictures of buckets filling up with photons or elctrons quite misleading, IMHO. Never liked them any way . .
Well, that sensitivity in uv/e is presumably the absolute value of that parameter. The actual number is negative.
Understood, thanks.
You may find this paper interesting:
Best regards,
Doug
Excellent paper, thanks again.
best,
Ted