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Today's Topics:
1. Re: Art Duplication (Spinnaker Photo Imaging Center)
2. Re: Colorsync-users Digest, Vol 12, Issue 114
(Millers' Photography L.L.C.)
3. Re: Art Duplication (Ben Goren)
4. Re: Art Duplication (Spinnaker Photo Imaging Center)
5. Re: Art Duplication (Ben Goren)
6. Re: Art Duplication (Robin Myers)
7. Re: Art Duplication (Ben Goren)
8. Re: Art Duplication (Spinnaker Photo Imaging Center)
9. Re: Art Duplication (Ben Goren)
----------------------------------------------------------------------
Message: 1
Date: Fri, 18 Sep 2015 12:25:06 -0700
From: Spinnaker Photo Imaging Center
<email@hidden>
To: Louis Dina <email@hidden>, email@hidden, email@hidden,
John Castronovo <email@hidden>, Andrew Rodney
<email@hidden>
Cc: colorsync-users <email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset=utf-8
I thank everyone for their information and education.
I use the Paul C. Buff, White-lightning Ultra1800, each flash tube is UV
coated. Reflectors are 7 inches. Polarizing filter sheets are over each
reflector.
A Schneider B+W UV-IR-CUT filter is mounted first on EF 100 mm f/2.8 Micro
L lens, and finally the circular polarizing filter.
I might just see where some of my issues come in. Could it be the
cardboard x-rite CC? (I refuse to use the passport CC).
Workflow is camera white balanced with what is supposed to be a white
target on one side, and black, gray, and white on the other side. These
three shades are for me to determine, exposure. Then, I use the white
only side to determine white balance in camera.
Next I image the x-rite cardboard CC. Though, sometimes I have the
cardboard CC included in the area along with the original art.
I have two different ways I work with the RAW file. Open in RPP 64 and
create the lighting-lens-camera profile with RPP 64. I set RPP 64 for
Kodachrome 64. Save the digital file as an RGB TIFF16-bit (BetaRGB). I
had been saving the file as Lab TIFF 16-bit.
LR 6 is next, and sizing is done in PS CS5.
I do my best not to change what is digitally captured, in order to
preserve the likeness of the original art.
The other way I have my workflow, use LR 6. LR 6 will blend multiple RAW’s
in RAW. Skip RPP 64 altogether.
Comments are made that the x-rite CC is not the same as the pigments in
the original art work. Therefore I wonder if this may be an issue?
Those using Einsteins’, what size reflector is used?
Many years back, someone in the museum industry, on this forum, told me to
use the Schneider B+W UV-IR-CUT filter. Anyone remember who that was?
Anyone also using the Schneider B+W UV-IR-CUT filter? Might have been in
regards to cobalt blue.
An NEC PA271w, and an NEC PA2721w are profiled with i1Pro and i1 Profiler.
Two separate work stations. The Epson Pro 9900 is profiled for each
different substrate, with i1 Profiler and read with the i1Pro.
EOS 6D’s are my cameras.
Questions?
Kind Regards,
David
David B. Miller, Pharm. D.
3809 Alabama Street
Bellingham, Washington, 98226-4585
360 739 2826,
------------------------------
Message: 2
Date: Fri, 18 Sep 2015 12:31:10 -0700
From: "Millers' Photography L.L.C." <email@hidden>
To: colorsync-users <email@hidden>,
email@hidden
Subject: Re: Colorsync-users Digest, Vol 12, Issue 114
Message-ID: <email@hidden>
Content-Type: text/plain; charset=utf-8
Jon, please describe in detail your method written below…….(1/5 exposure)
and cross polarized (4/5)
On Sep 18, 2015, at 12:00 PM, email@hidden
wrote:
In addition to the previously stated, my 4x5 fine art repro days included
a blend of specular directional (1/5 exposure) and cross polarized (4/5).
This captured better brush stroke textures.
Jon
David B. Miller, Pharm. D.
3809 Alabama Street
Bellingham, Washington, 98226-4585
360 739 2826
------------------------------
Message: 3
Date: Fri, 18 Sep 2015 12:50:33 -0700
From: Ben Goren <email@hidden>
To: colorsync-users <email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset="utf-8"
On Sep 18, 2015, at 12:25 PM, Spinnaker Photo Imaging Center
<email@hidden> wrote:
Workflow is camera white balanced with what is supposed to be a white
target on one side, and black, gray, and white on the other side.
While some white balance targets are more spectrally flat than others,
nothing, not even Spectralon, is perfectly flat. Click-to-white-balance
relies on a nonexistent physical property.
If you know the camera's spectral response and the spectrum of the
illuminant, you can predict the correct per-channel scaling factors for
white balance without even taking a picture. If you photograph a sample
with a known spectrum, you can compare the predicted and actual RGB values
to automatically fine-tune the white balance. And if you have a number
such samples -- such as with an entire ColorChecker -- you can average
them for even greater precision. Of course, this same process will
normalize exposure as well.
Comments are made that the x-rite CC is not the same as the pigments in
the original art work. Therefore I wonder if this may be an issue?
They're not exactly the same, but, then again, there's variation across
manufacturing batches, changes with time and exposure to the elements, and
so on. For typical photographic purposes, the differences can typically be
ignored. For critical work, you'll want to use your own measurements of
your own chart.
The original 8x10 cardboard ColorChecker is superb when you want a large,
physically thin and flat reference, especially for normalizing white
balance and exposure. The ColorChecker Passport is, hands down, the best
chart for field use as well as the best small chart for profiling. The
extra couple dozen patches on the new half both give you as big a gamut
with as saturated colors as you're reasonably going to get with such a
device as well as an excellent sampling of the neutral axis. The
integrated case gives it as much durability as you can reasonably expect.
I've dragged mine all over the Desert Southwest....
The two ColorCheckers serve different-but-overlapping purposes. If I could
only have one, I'd easily go with the Passport. I have both and use both.
I've made my own charts in the past. Were I continuing to use a profiling
workflow based on reflective charts, I'd still use homebrew charts; you
simply can't buy anything remotely in the same league as what you can make
with a trip to the art store. But that workflow falls quite short of
spectral modeling...and, as such, all I need charts for now are to
fine-tune exposure and white balance. I can do that with a single patch
better than you can with a click-to-white-balance, but it's just as easy
to do it with an entire ColorChecker -- which gives negligibly fractional
DE accuracy for colors near the neutral axis. Of course, the closer you
get to the spectrum locus, other factors come into play....
Cheers,
b&
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Message: 4
Date: Fri, 18 Sep 2015 13:27:11 -0700
From: Spinnaker Photo Imaging Center
<email@hidden>
To: Ben Goren <email@hidden>
Cc: colorsync-users <email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset=utf-8
Ben, for years you have written about home brew CC. I have never tried it
since I would not know what color to purchase….oil, or watercolor, or
pastels.
I would not know how this home brew chart could be read. Or what to read
it with.
Cheers.
David
David B. Miller, Pharm. D.
3809 Alabama Street
Bellingham, Washington, 98226-4585
360 739 2826
------------------------------
Message: 5
Date: Fri, 18 Sep 2015 14:17:31 -0700
From: Ben Goren <email@hidden>
To: colorsync-users List <email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset="windows-1252"
On Sep 18, 2015, at 1:27 PM, Spinnaker Photo Imaging Center
<email@hidden> wrote:
Ben, for years you have written about home brew CC. I have never tried
it since I would not know what color to purchase….oil, or watercolor, or
pastels.
I would not know how this home brew chart could be read. Or what to read
it with.
If it's an actual 24-patch ColorChecker, unless you're going to be making
it in volume, buy the real deal. If you'll be making them in volume, take
your ColorChecker to the local home paint store (be sure it's a new one
with an expanded gamut) and have them match the patches on their own color
matching system; they'll mix up spectral matches for you using their own
X-Rite branded hardware and software. If you plan on doing that for other
than personal / internal use, run it by a lawyer; I've no clue what
X-Rite's own lawyers might think if you started selling them. But, if you
want to sell charts...the patch selection of the original ColorChecker is
good but certainly can be improved upon; you'd be much better off making
something original.
If you want an high-patch-count chart with a large gamut and lots of
interesting spectra, go to the local art store and buy lots of paints and
some brushes and so on and paint a bunch of squares. Mix the paints in as
many permutations of proportions as you've patience for -- and be sure to
do multiple tints, especially of the darker colors, to bring up the
chroma. Golden Fluid Acrylics is a good choice. Or, enlist the help of a
local artist who's already got an extensive palette.
In either case, you'll need to measure the patches with a spectrometer
(such as an i1 Pro). For the homebrew chart, you'll also need to create
the necessary chart recognition files for your profiling software. With
Argyll, it's straightforward but the file format is very unforgiving; if
it doesn't work right, it's because there's something not right in the
files, and it may take some careful inspection to spot where you've gone
worng.
If you're going the homebrew route...don't think you have to make a single
oversized chart with lots of teeny tiny patches to get a good patch count.
A much better approach is multiple charts with large patches; combining
the readings from multiple charts into a single input file for color
profiling is trivial -- at least, it is with Argyll. Were I to do it
again...I'd probably do 8" x 10" charts with ~1" patches = 80 patches /
chart, and then make however many charts (each with a different selection
of paints) as I felt inclined to make.
If you're feeling extra inspired, you can make an overlay cutout like on
the ColorChecker charts, either by hand with a razor or with a
computerized paper cutter such as is popular amongst the scrapbooking
crowd. Or you could start by putting down some masking tape to outline the
patches, and discard the masking tape when done. Either method will make
it much easier to get good clean straight edges to help the edge detection
algorithms identify the chart's location and orientation. But, even if
not, you can digitally overlay a similar mask in Photoshop or Affinity
Photo or the like before feeding the picture to the profiling engine.
But...again, chart-based profiling is suboptimal in many ways, and not at
all what I do today....
Cheers,
b&
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Message: 6
Date: Fri, 18 Sep 2015 14:26:17 -0700
From: Robin Myers <email@hidden>
To: "'colorsync-users?lists.apple.com' List"
<email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset=windows-1252
Dr. Miller:
<snipped>
I might just see where some of my issues come in. Could it be the
cardboard x-rite CC? (I refuse to use the passport CC).
The ColorChecker Passport uses the same patches on its ColorChecker
Classic page as the cardboard ColorChecker Classic so there is no reason
not to use the ColorChecker Passport. There are added benefits on the
facing Photo Enhancement page with finer spaced dark grays and light grays
and the higher saturated spectrum colors. These extra patches can be used
to evaluate your images and profiles. More information on the ColorChecker
Passport may be found at
http://rmimaging.com/information/ColorChecker_Passport_Technical_Report.pdf.
Workflow is camera white balanced with what is supposed to be a white
target on one side, and black, gray, and white on the other side. These
three shades are for me to determine, exposure. Then, I use the white
only side to determine white balance in camera.
This is one source of your color error. If you examine the spectra of the
white patch on this chart you will find that it is not white but very pale
yellow. The color is specified as Munsell N9.5 and an average of 12
ColorCheckers of various ages produces L*a*b* values of L* 96.4, a* -1.0,
b* 3.1. We perceive the color as white because it is the whitest object in
our field of view and the human vision system adapts to make it appear
white. Because the white patch is not white, the white patch should be
used for setting the exposure only.
Instead, you should set the neutral balance, white balance is a misnomer,
with the gray patch on this chart. The gray patch is specified as Munsell
N5 which I have measured and averaged from 12 ColorCheckers as L*
50.9, -0.4, 0.1. This is definitely more neutral than the white patch and
a better choice for neutral balancing. It is also light enough to produce
a good signal-to-noise ratio in the camera’s sensor.
The black patch is specified as Munsell N2 and should be used to check for
veiling glare. Veiling glare can be controlled by using a lens hood and
surrounding the subject with a black background.
<snipped>
Mr. Goren:
<snipped>
Workflow is camera white balanced with what is supposed to be a white
target on one side, and black, gray, and white on the other side.
While some white balance targets are more spectrally flat than others,
nothing, not even Spectralon, is perfectly flat. Click-to-white-balance
relies on a nonexistent physical property.
While PTFE references such as Spectralon® and Fluorilon® do not exhibit
perfectly flat spectral reflectances, they are the best materials
presently available for white reflectance standards and are used as such
for calibrating spectrometers by many companies and NIST. PTFE is the only
white material I recommend for neutral balancing cameras. The majority of
white objects, including the white patch on ColorChecker charts, use a
titanium white pigment which is actually a pale yellow, as noted above. If
these white objects are used for neutral balancing a camera the resulting
images will have a slight blue color cast.
Robin Myers
------------------------------
Message: 7
Date: Fri, 18 Sep 2015 15:11:14 -0700
From: Ben Goren <email@hidden>
To: "'colorsync-users?lists.apple.com' List"
<email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset="iso-8859-1"
On Sep 18, 2015, at 2:26 PM, Robin Myers <email@hidden> wrote:
While PTFE references such as Spectralon® and Fluorilon® do not exhibit
perfectly flat spectral reflectances, they are the best materials
presently available for white reflectance standards and are used as such
for calibrating spectrometers by many companies and NIST.
PTFE makes for a great reference standard, but, best I know, outside of
photographic click-to-balance workflows, it is not used in a manner that
assumes that it is pure white.
If you measure the calibration tile included with an i1 Pro -- the one
that you have to put the instrument on before every session -- you'll see
that it's decidedly less white than PTFE. It's got a curved spectral
reflectivity significantly less than 100%. But it's a beautifully smooth
spectrum, and presumably the material is very stable. It's plenty
reflective enough that it presents an high signal-to-noise ratio for the
electronics. PTFE is also stable and has an even higher reflectivity,
making for marginally better absolute properties. But it's less durable
than the ceramic used for the i1, and I'm sure much more expensive, which
would explain why X-Rite used the ceramic instead.
You don't need an absolute white reference for spectrometry. The
instrument (or software) knows what the combined reflected spectrum of its
lamp and reference is supposed to be; whatever it measures at the time of
calibration is used to create an offset to correct for whatever momentary
conditions from the environment or whatever are causing drift. You could
use a lump of coal or a colored ink or whatever for that, save the
readings would get noisy.
<blockquote>PTFE is the only white material I recommend for neutral
balancing cameras.</blockquote>
If you're doing the click-to-balance method, PTFE is as good as it gets.
Thread seal tape (like what plumbers use) is a good, cheap source; layer
it up to ensure opacity. BabelColor used to sell an affordable 1" circular
Spectralon (or equivalent) target, but that was years ago. Actual
Spectralon targets are available for insane prices.
But...there're two cheap alternatives that every photographer should be
aware of.
First is Tyvek. It's nearly as good as PTFE, and you can buy it cheap,
usually in the form of envelopes, at your local office supply store. It's
nearly indestructible, which is why it's used for envelopes. It's got a
bit of specularity to it, including grain in the specularity, so you have
to be careful with lighting. At the same time, if it throws no specular
highlights, neither will whatever you photograph.
Second...is styrofoam. I'm not aware of any commercially-available white
balance target other than Spectralon that's as good as a styrofoam coffee
cup. As a bonus, the conical shape lets you get directional samples in
mixed lighting. Or a styrofoam sphere from a crafts store could do the
same.
Again again, best is to predict the RGB values for the scene's combination
of the camera's spectral response plus the illuminant's spectra and the
spectral reflectivity of a number of patches. Click-to-balance is a
shortcut for an unique class of circumstances that doesn't actually exist,
though there're a number of easy-to-attain not-entirely unreasonable set
of approximations that are "good enough" for non-critical work.
Cheers,
b&
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Message: 8
Date: Fri, 18 Sep 2015 15:47:58 -0700
From: Spinnaker Photo Imaging Center
<email@hidden>
To: Ben Goren <email@hidden>
Cc: colorsync-users List <email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset=windows-1252
Thank you Ben.
Chart would be only for my personal use……..Now, if I missed it, what do
you do today?
On Sep 18, 2015, at 2:17 PM, Ben Goren <email@hidden> wrote:
what I do today....
David B. Miller, Pharm. D.
3809 Alabama Street
Bellingham, Washington, 98226-4585
360 739 2826
------------------------------
Message: 9
Date: Fri, 18 Sep 2015 16:35:40 -0700
From: Ben Goren <email@hidden>
To: colorsync-users List <email@hidden>
Subject: Re: Art Duplication
Message-ID: <email@hidden>
Content-Type: text/plain; charset="windows-1252"
On Sep 18, 2015, at 3:47 PM, Spinnaker Photo Imaging Center
<email@hidden> wrote:
Thank you Ben.
Chart would be only for my personal use……..Now, if I missed it, what do
you do today?
Short version...I take a picture of a diffuse light source viewed through
a spectroscope and extract RGB values from it. That plus an i1 Pro
measurement of the light source and separate measurements of the
transmission efficiencies of the diffraction grating and the lens gets me
the camera's per-channel spectral sensitivities. Once you've got that, you
can combine it with the spectrum of any illuminant and the efficiency of
any lens / filter combination to predict RGB values for any known
reflective spectrum. And I do so for tens of thousands of virtual samples
to create a virtual chart with that many patches and use Argyll to build a
profile from that. It's specific to the illuminant and lens, but then so
is any profile.
I'll be doing a full writeup in the hopefully-not-too-distant future....
Cheers,
b&
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