[argyllcms] Re: Profiling backlit film with Monitor
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 26 Nov 2017 14:44:21 -0700
On Nov 23, 2017, at 5:17 AM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote:
A good quality light box may be a better bet
In that vein, it wouldn't be all that difficult to create an high-quality light
box using your favorite rapid prototyping construction method. (For me, that's
foamcore, an Xacto, and gaffer's tape.) You'd want a double diffusion geometry
and tungsten bulbs. Your diffusers should ideally be spectrally flat...a couple
of the thinnest sheets of HDPE your local industrial plastic supply store is
willing to sell you (or let you have from the scrap pile) should work. PTFE
would be good, too, but a thin enough sheet is probably too fragile.
A simpler and quicker alternative, but more expensive out of pocket, would be
to get a photographic softbox, again with double diffusion.
An important note: tungsten bulbs, especially ones bright enough to use for
such a purpose, get hot. Make sure there's plenty of airflow past the bulb.
Consider a fan; if no fan, don't let it run long enough to heat up the inside
of the box. No matter what, don't leave it on unattended -- and that would
apply to commercial lightboxes, too!
Why tungsten? The cheap, unfiltered ones bulbs as close to perfect examples of
Illuminant A / blackbody light sources as makes no difference. The math to map
to any other illuminant, regardless of spectrum / color temperature / whatever,
is trivial. And there's no danger of weird metamerism effects due to holey or
spikey source spectra. Aside from stabilized xenon photographic flashes, all
other readily-available light sources suffer serious problems, from spectral
discontinuities (all consumer sources that aren't unfiltered incandescent) to
inconsistency (all natural sources and many consumer sources) to cost (anything
else you can buy that doesn't have those problems).
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