Quote Originally Posted by SuzanneR View Post
Ok... I'll confess, I don't fully understand the technical jargon here!!
For the sake of clear discussion, I will offer a little dictionary

ADC= analogue to digital converter, takes an analogue signal and 'bins' it. In the simplest case a b&w image is 'bitmapped' into a 1-bit file... ones and zeros. ADCs take a *huge* amount of information and compress it into a much smaller series of bins, with which you can quickly do logical operations.

Bit depth= how many bits the ADC translates the analogue file into. 1-bit means the image gets rendered in terms of only 2^1=2= two tones, i.e. pure white and pure black dots.... 'line art.' 8-bit means that you have 2^8=256 different tones.

LVT= light valve technology, a method for 'printing' on traditional negative material with very high resolution. LVTs predate digital cameras by many decades. You can still have LVTs made. The cost is about the same as a drum scan.

Drum scanner= scanner that uses no image lensing to collect the information from the negative or positive. A PMT detector, with ~zero noise, records the information as it is rastered to the very limits of optical resolution. At this stage the signal is still fully analogue; however, when you store it, it gets binned and hence meets an ADC. At that stage the file is digital. Drum scanners can deliver far more resolution than can be stored in any practical way... short of piping the signal directly to an LVT and essentially recreating the negative kind of like teleportation

I do not have the security clearance to verify the following assertion, but I would say that there must be (or must have been at some stage) a Drum/LVT coupled pair that was used in aerial recon, linked by purely analogue transmission. In other words: there was a full-res LF neg created by a satellite that was then drummed onboard and recreated on the ground by LVT for enlargement. My guess is that such a setup has been superceded by a multi-sampling digital process with the added advantage of high IR sensitivity at the imaging stage.