RE: One more thing about light boxes.

["Creager, Robert S" <CreagRS@LOUISVILLE.STORTEK.COM>]

Hey Paul,

Hmm...  I'll expose my ignorance.  What about ND filters?  And/or what if
you used Chris's idea of a ball, with the flash off-axis 90 degrees from the
camera, so no direct energy enters the ccd, just reflected?

And, just to prolong this conversation...  If a good system for flats was
achieved, wouldn't you just run this all day taking flats (~300 of them for
a 12 hour run), then all night taking sky pictures?  Seems like the more
flat data, the better.  To achieve 120 flat exposures (per 'The Paper'),
you'd need 100 second exposure (same time as the observation exposure,
right?), and 30 second read-out (give or take), giving 4 1/2 hours a day of
bulb burn.  How long can you expect to get 'quality light' from a light
bulb?  Would those 'natural sunlight' bulbs work better, worse?

Just wondering,
rob

> -----Original Message-----
> From: Paul Repacholi [mailto:prep@prep.synonet.com]
> Sent: Friday, November 09, 2001 1:11 PM
> To: Creager, Robert S
> Cc: tass@listserv.wwa.com
> Subject: Re: One more thing about light boxes.
> 
> 
> 
> > A remarkable lack of comments for this idea (or are we waiting for
> > Arne to come back and weigh in).  This seems like a reasonable idea
> > (from a physical sense, not necessarily a logical sense), and I'm
> > betting we can trigger the flash(s) from a parallel port.  Just to
> > spark some noise, what about using disposable flash bulbs (those
> > cubes or strips)?  Or do they make those anymore?
> 
> You NEVER let anyone with a flash gun into a dark room, or near photo-
> receptors. If they use flash bulbs, remove there money first, then
> throw them out...
> 
> The peak light output from even a small flash tube can induce latch-
> up in CMOS chips and destroy them. And it could take weeks for the
> CCDs to recover from it. Plus the possible effects of the current
> pulse when you fire it.
> 
> For flash bulbs, how would you calibrate each one? Plus the cost!
> There was a good reason photographers took to electronic flash as fast
> as they could!
> 
> An under-run tungsten bulb will do fine for this. I have seen 
> dome flats
> done from a 15W globe on the floor shining up into the dome. 
> You do not
> need a lot of light at all.
> 
> -- 
> Paul Repacholi                               1 Crescent Rd.,
> +61 (08) 9257-1001                           Kalamunda.
>                                              West Australia 6076
> Raw, Cooked or Well-done, it's all half baked.
> EPIC, The Architecture of the future, always has been, always will be.
>