RE: filmscanners: LED Illumination for Film Scanners

[rafeb <rafeb@channel1.com>]

At 05:01 PM 6/20/01 -0400, Austin wrote:

>Yes, and incandescent light bulbs used in an enlarger get a condenser
>system, which is entirely different than a cold light head, which is
>basically what most scanners use for illumination.


Ah, but the "dynamics" of a conventional enlarger 
are rather different from a film scanner, no?

In an enlarger, exposures take seconds, or tens 
of seconds.  Fluctuations in the lamp intensity 
will average out, but they cannot cause "banding" 
in the print.

Spatial non-uniformities (in an enlarger) will be 
dealt with by the diffuser or condenser.  Any 
non-uniformities (at the print) can be attributed 
to a poor diffuser or condenser design.

In a film scanner, fluctuations in intensity, or 
spatial non-uniformities that vary in time (during 
the course of the scan) will cause banding.  It's 
not a hypothetical situation -- I've seen this effect 
in both of my previous film scanners, which used 
fluorescent light sources.

This is a rare and anomalous situation (at least in 
the better scanners) but it does occur.

I wonder if the Leaf benefits from that ridiculously 
huge bulb -- as opposed to the dinky little 4 inch 
F4T5 tube used in the older SprintScans and Microtek 
machines.


rafe b.