[Tfug] Yet another optics question

[Bexley Hall]

> With my totally unqualified opinion, I would go with what the 
> guy in the climate change business, (ostensibly) said...
> 
> Just go with the 1460X six volt lamp as B&L designed.
> It's really common and easy to get by mail order. Its color
> characteristics are probably consistent. Kind of looks like
> an automotive lamp base with a flange...

The lamps run anywhere from $5 to $??? (some fools trying
to peddle them for $20!).  The old lamp was an "S1460" -- I
have not been able to get any clarification as to the
differences between the S1460 and 1460X... perhaps just
differences in manufacturer's part numbering schemes?

The kicker with mail order is the $8 - $10 they want to ship
the 1 ounce bulb!

And, *using* the 20W device throws off a fair bit of heat
(the lamp is sited just below/in front of your forehead)
which makes it quite uncomfortable.
 
> Having said that, the lens assembly is probably like that
> of a photo enlarger condenser. As I understand it, it takes
> a point source and gives light focused at infinity. Good as
> an illuminator.

Yes.  My question is:  how critical is the location of
that point source?

> If you wanted to play around have money to blow you could
> get a cheap high power LED emitter from a place like Deal
> Extreme. Place it at the focus where the lamp filament is.
> Give it an appropriate heat sink. The microscope power
> supply might work too.
> 
> Have fun!

I suspect I don't even have to go to the extreme of a fancy
emitter.  I tried an LED flashlight and it seemed to work OK.
Granted, more light would be nicer but I don't really see the
advantage of TONS of light (?).  The brochure explains that
it "helps cast shadows" (?)  OK, maybe that helps with depth 
cues??