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> 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 <argyllcms-bounce@xxxxxxxxxxxxx> *On
Behalf Of *Kamil Tresnak
*Sent:* Wednesday, October 30, 2019 2:01 PM
*To:* 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> 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 <argyllcms-bounce@xxxxxxxxxxxxx> On
Behalf Of Ben Goren
Sent: Friday, October 4, 2019 2:10 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Backlit (transmission) profiling with i1
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&
