[argyllcms] Re: Backlit (transmission) profiling with i1
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 4 Oct 2019 11:09:32 -0700
On Oct 4, 2019, at 9:11 AM, Alexey Gribunin <Gribunin@xxxxxxx> wrote:
Now I'm using iPad (!) and found it much more stable (auto-brightness=off).
Curious that at an LED display should work well as a backlight for transmissive
profiling. The spectrum is going to be spiky as all get-out, no?
Light boxes are readily available, and an almost trivial DIY project. The
biggest challenge these days would be finding incandescent bulbs. You’ll want
to provide lots of ventilation in the illumination chamber, possibly even
including an exhaust fan if you’re pumping enough wattage into the box. But the
design...just get a pair of same-sized translucent plastic sheets. Using your
favorite construction method (could be anywhere from foamcore held together
with duct tape to fine woodworking dovetail joinery), build a box that holds
the one sheet at the top, the other in the middle, and the bulb(s) at the
bottom. If the construction material isn’t already white, paint the inside
white (cheap interior house paint is fine). If the box isn’t bright enough, you
need either more transparent sheets (start with the middle diffuser) or more
wattage (be careful of heat!). If you have visible bright spots, you need a
middle diffuser that’s more opaque.
That’s all there is to it.
I would again very, very highly recommend unfiltered incandescent lights for
profiling purposes. The spectrum is beautifully smooth as a fundamental
property of the physics. That it’s not necessarily the ideal color temperature,
etc., is entirely irrelevant; the math to fix that is trivial. Spectral
spikiness...can cause all kinds of problems.
I would even recommend “hot” incandescents for color critical photography over
the best flashes. Not that the best flashes are problematic; they’re just not
as spectrally smooth as incandescents. (Of course, non-color considerations
could quickly tip the scales to flashes. I wouldn’t try to photograph humans in
a studio setting with hot lights, for example.)
Cheers,
b&
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