Ilah!
I'm sorry, I was NOT commenting on the application of the lamps for the purpose
of transparent media but for the purpose of serving as an alternative to GTI
and JUST fluorescent tubes for graphic arts, for illuminating the surface of a
viewing booth or a press console, since that's the standard (ISO-3664) that
they refer to on their site.
I'm still interested even though it's horribly expensive.
The 24" tube is selling for $119.00 + shipping....
Thank you so much for the URL.
/ Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx> On Behalf
Of Iliah Borg
Sent: Wednesday, October 30, 2019 7:52 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Backlit (transmission) profiling with i1
Hi Roger,
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".
Oops! Small problem...
Illuminance is specified at 1.1m and is only ~350 lux?
That's way too small ☹ to be useful?
My GTI garbage luminaire gives me 1300 Lux at 1.1m?
/ Roger
---
I was wrong, they *do* offer an ISO-3664:2009 compliant solution:
https://store.yujiintl.com/collections/standard-illuminant/products/st
andard-illuminant-cri-98-d50-5000k-t8-led-tube-pro-iso3664-2009
But it's in the form of a T8 tube (they don't have it in "LED strip".
I think I'd be interested in ordering a small tube, to experiment with.
Thanks Ilah!
/ Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx>
On Behalf Of graxx@xxxxxxxxxxxx
Sent: Wednesday, October 30, 2019 2:42 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Backlit (transmission) profiling with i1
Ilah,
These "Yuji VTC D50 LED" are promising.
Not cheap, though ☹
They are smart to state "ISO-3664:2000", which means they have not figured
out how to be "ISO-3664:2009" compliant yet?
Best / Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx>
On Behalf Of Iliah Borg
Sent: Wednesday, October 30, 2019 2:32 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Backlit (transmission) profiling with i1
In my experience even Yuji COBs (we use those for our projects) can't be used
without a spectrometer.
Check the spectra here:
https://store.yujiintl.com/collections/standard-illuminant
For a camera, one needs at least 400 .. 700 nm range
On Oct 30, 2019, at 2:15 PM, Kamil Tresnak wrote:
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/vie
w
?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&
--
Best regards,
Iliah Borg
LibRaw, LLC
www.libraw.org
www.rawdigger.com
www.fastrawviewer.com
