[argyllcms] Re: Backlit (transmission) profiling with i1
- From: <graxx@xxxxxxxxxxxx>
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Wed, 30 Oct 2019 14:18:42 -0400
Kamil,
This is not so bad?
Was this made using “strip reading” with the i1pro?
/ Roger
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx> On Behalf
Of Kamil Tresnak
Sent: Wednesday, October 30, 2019 2:15 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Backlit (transmission) profiling with i1
Czech friend from Prague 😂
*my led strips" was no good, profiles have problems in some parts of spectra
i1pro, fake transparent (as described in argyll manual, spot mode (we discussed
this some time ago), so time consuming, but strip reading never worked for me)
Here is an example - just a mobile photo of a quick view against an undefined
ceiling light ...
https://drive.google.com/file/d/1dDLBLD1cVR6kjtwcsYJik7PdfZotZtSN/view?usp=sharing
K.
On Wed, Oct 30, 2019 at 7:05 PM <graxx@xxxxxxxxxxxx <mailto:graxx@xxxxxxxxxxxx>
wrote:
Hello Kamil – russian friend! (Dobroi ultra, Kagh dielo?)
So “LED stripes” light was not good?
How were you taking measurements?
I1pro? In “Ambient” mode?
/ Roger
From: argyllcms-bounce@xxxxxxxxxxxxx <
mailto:argyllcms-bounce@xxxxxxxxxxxxx>
<argyllcms-bounce@xxxxxxxxxxxxx <
mailto:argyllcms-bounce@xxxxxxxxxxxxx> > On
Behalf Of Kamil Tresnak
Sent: Wednesday, October 30, 2019 2:01 PM
To: argyllcms@xxxxxxxxxxxxx <
mailto:argyllcms@xxxxxxxxxxxxx>
Subject: [argyllcms] Re: Backlit (transmission) profiling with i1
Hello Roger,
not talked a while, friend :)
Roger, go for incandescent, exactly as Ben recommended (even with fan 🙂 ), and
you will be a hero.
This is my real-world experience. I tried a few sources, even LED stripes, and
with bad results.
Of course, i don't know every LED source in the world, but i don't want waste
my time searching for a suitable one.
Best!
Kamil
On Fri, Oct 4, 2019 at 8:22 PM <graxx@xxxxxxxxxxxx <
mailto:graxx@xxxxxxxxxxxx>
wrote:
Ben,
I was asked recently whether I could create backlit profiles for transparency
media. As I don't have an instrument that can measure in transparency, I
thought I could use a non-contact colorimeter, I was thinking of mounting the
instrument on a tripod to always aim at the same angle, normal, relative to the
patches and all I would have to do was to move the target so that all patches
would be measured on the same "source of light". I don't see why that would not
work? But I was not sure about the light source itself? My thinking was to use
the same kind of fluorescent tubes used in these point of sale "backlights".
That way, by using the same type of lighting, I was guaranteed some success.
Now, why do you say that LED spectrum would be spiky? Fluorescent tubes
spectrum are, by nature, spiky. But LED? Seems to me they're rather smooth.
/ Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx <
mailto:argyllcms-bounce@xxxxxxxxxxxxx>
<argyllcms-bounce@xxxxxxxxxxxxx <
mailto:argyllcms-bounce@xxxxxxxxxxxxx> > On
Behalf Of Ben Goren
Sent: Friday, October 4, 2019 2:10 PM
To: argyllcms@xxxxxxxxxxxxx <
mailto:argyllcms@xxxxxxxxxxxxx>
Subject: [argyllcms] Re: Backlit (transmission) profiling with i1
On Oct 4, 2019, at 9:11 AM, Alexey Gribunin <Gribunin@xxxxxxx
<
mailto: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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