Re: Art Duplication
Re: Art Duplication
- Subject: Re: Art Duplication
- From: email@hidden
- Date: Thu, 17 Sep 2015 15:41:43 +0000 (UTC)
- Thread-topic: Art Duplication
The fact that the Color Checker reproduction appears OK argues against this problem being due to color appearance effects, but I would note that the deficiencies you see are of the type caused by color appearance changes due to viewing conditions. That is, a strict colorimetric reproduction of a scene as a print or monitor image usually appears to have less contrast and lower saturation than the source appeared to have. Viewing an image on a bright display with a dim surround in particular causes the lowlights to appear washed out, something that has been known since the early days of television.
Again, your description of the correct-looking CC reproduction argues against this interpretation, but I just wanted to mention it for consideration.
Wayne Bretl
----- Original Message -----
From: "John Castronovo" <email@hidden>
To: "Louis Dina" <email@hidden>, "Colorsync Users List" <email@hidden>
Sent: Thursday, September 17, 2015 9:49:10 AM
Subject: Re: Art Duplication
It isn't clear from your post that you made your custom camera profile using
the identical cross-polarized setup that was used to capture the art, but
assuming that was done, I'll just add that original art is different from a
color checker in so many ways that it's a no brainer to me that one has to
make final adjustments to the scan in order to best match the original. Some
paintings require more tweaking than others, but they all need something and
profiles alone can only get us very close to the optimal result. You also
don't need to visit LR. Just assign your custom profile in Photoshop and
then convert to a wide gamut working profile and go from there. Then I add a
levels adjustment layer to set my black and white points and that gets me
very close. You won't find a one size fits all for fine art reproduction
though. It's always an interpretation.
That said, your results are the opposite of what I'd expect. A cross
polarized setup yields too much contrast rather than too little, so you
might have too much flare or else you're not fully polarized. Maybe there's
a lot of un-polarized spill light coming from flash units, so check that
out. Also, you may discover that getting farther away from the original with
a longer lens helps with reflections and minimizes the need for polarizers
and get the lights closer to the wall than 45 degrees, but be sure to use
gobos to prevent flare causing light from reaching the camera.
john castronovo
techphoto, llc
-----Original Message-----
From: Louis Dina
Sent: Thursday, September 17, 2015 10:14 AM
To: Colorsync Users List
Subject: Art Duplication
I want to duplicate some oil paintings on canvas. The surface is
reflective, glossy, textured paints, and in places, the dimples of the
canvas are visible. The oil paintings are coated with a gloss varnish of
some sort. My tools are limited, but they'll have to do. I just want to get
as close as I can using the tools I have. First, some background.
I'm using a Canon 5Dmk2, 85mm prime lens with circular polarizer, two Alien
Bee studio strobes on either side with polarizer gels (cross polarized to
eliminate reflections and glare) aimed at 45°angles. I'm photographing the
artwork with a small Color Checker and a Spyder Cube (for the light trap)
to help me assess tone and color.
I built a custom camera profile using XRite Color Checker Passport and I'm
processing the images in LightRoom. I know, not perfect.
In the past, I had a tough time getting even a lone color checker to
reproduce fairly accurately until I forced the 6 neutral patches to match
the L* values of my CC target (which I read with my Eye One with UV Cut
filter). Once I got the L* values of the 6 neutral patches right, the 18
color patches measured fairly close to my spectro readings. Close enough
for me. My conclusion is that the default LR settings are so contrasty,
even with a "linear" Tone Curve, that it pumps everything way up and whacks
the colors.
In LR, I apply my custom camera profile, Click-WB on the 50% gray patch
(which is the closest to dead neutral on my CC target), then manually
adjust the Tone Curve to match the neutral L* values of my CC to match my
spectro readings. My first photos of the artwork had some
flare/glare/reflection due to the high gloss shine, so when I got the CC
Target looking right, the paintings looked washed out and flat. I assumed
this was the reason the CC looked right, but the painting did not. That's
when I decided to try polarized light sources and a polarizer on the camera
lens. It definitely helped and I am pleased with the improvement.
However, even with the polarized images, if I force the L* values of the 6
neutral CC patches to match my spectro readings, the images still look a
bit flat and washed out. The CC itself looks great and all the patches
measure pretty close.
I can adjust the image so it DOES look pretty accurate by eyeball, but then
the contrast of the color checker ends up being high. Mainly, I have to
darken the darken the black and Dark Gray patches so the painting looks
right. I'm hoping to come up with a method that doesn't rely so much on
memory and feel.
I'm baffled as to why this would be? (unless I still have some flare). Any
thoughts or suggestions? (additional equipment or software is not a
consideration at this time).
Thanks,
Lou Dina
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