Ok, here is the problem
I am very thank full of Mike Collete from BetterLight that has accepted me in the owners forum. I don't have a scanning back, but have to find a digital capture to photograph art work for galleries.
He answer one of my most important questions regarding the (informal) feasibility study of a scanning back.
The problem that I have is that I wish to work more on location than in studio for various reasons, so the capture system has to fit well in a taxi cabs trunk.
I don't know if carbon copy Mike Collete's response here is good or bad, but probably anyone that has ever used a scanning back knows what he said and is no proprietary secret... so here it is..
A - Tungsten hot lights will work OK, but location shoots often have
problems with not having enough different circuits to power the
required
number of tungsten lights, and/or problems with AC mains voltage
variations
that can cause tungsten lights to vary in intensity during a scan,
producing
faint dark/light banding whenever the lights change brightness.
Lowel's
Tota lights sure are compact, but these little lights aren't very
efficient,
and you'll need to use four to six of these to produce enough light to
scan
a 30 x 40 inch subject (for example). Lowel's somewhat larger "DP"
tungsten
lights are much more efficient than the Tota lights, although you'd
still
probably want to use four of these (750-watt) fixtures to cover a 30 x
40
inch area.
There are much more efficient alternatives to tungsten lights that also
tend
to produce better color rendition, although these alternative lights
aren't
usually as small as tungsten fixtures. Some relatively compact
fluorescent
fixtures are now available, as well as some of the newer HID (High
Intensity
Discharge) fixtures. "
Since 30 x 40 inch is a small area, I would have to bring MORE than the 4,500 Watts (750w x 6 in case of Totas) and expect the gallery to be able to handle that much juice etc etc.
So what I'm thinking now is that shouldn't it be better to go in the one - shot back direction?
I could wait a few months, establish my practice using film and get a 22mb back for my Mamiya 645 AFD, -- may be a P25 or even a ZD from Mamiya, if the company resuscitates, that is...
... (the expressos made me do it...)