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Author Topic: Accurate Colors  (Read 34480 times)
ormike
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« on: July 08, 2009, 07:50:38 PM »
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Hi Folks,
I am a printer and not a photographer by trade and I use a Canon 5D to photograph paintings under consistent studio lighting for the purpose of reproduction on a Epson 9600 or 9900.
I am searching for the best workflow to achieve ACCURATE colors as opposed to pleasing colors.
I currently use a 24 patch Macbeth color checker to build camera profiles and have used the furnished Lab target values as well as reading the Lab values of the Color Checker myself and have built numerous camera profiles using Monaco with fair but not great results.
I find I need to spend way too much time color correcting the prints  in Photoshop to get the colors where they need to be which is the color of the painting.
I have used ACR with its imbedded profiles and RAW Developer with all the profiles stripped out.
I am considering going to a Hutch Color reflective target because each individual patch has been measured on each target or to the Color Checker SG target.
Actually I'm willing to try just about anything to get accurate repeatable colors.
Your comments will be very much appreciated.
« Last Edit: July 09, 2009, 04:53:37 AM by ormike » Logged
Jack Flesher
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« Reply #1 on: July 08, 2009, 10:52:40 PM »
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First you will need a proper color-managed workflow from capture through output.  So in addition to quality monitor and output profiles that you're probably already familiar with, you'll want a dedicated capture profile built specifically for your camera and the lights you'll be shooting under, and ideally built using the lens you'll be shooting with most of the time...  This is a real icc profile you can apply to the image, not just the simple set of camera corrections you create in ACR or LR and apply during conversion.  And be forewarned that unlike paper or monitor profiles, camera profiles can be a *bitch* to get just right and usually require significant time spent editing the profile for optimal results...

Cheers,
« Last Edit: July 08, 2009, 11:00:44 PM by Jack Flesher » Logged

PeterAit
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« Reply #2 on: July 09, 2009, 07:27:20 AM »
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Quote from: Jack Flesher
First you will need a proper color-managed workflow from capture through output.  So in addition to quality monitor and output profiles that you're probably already familiar with, you'll want a dedicated capture profile built specifically for your camera and the lights you'll be shooting under, and ideally built using the lens you'll be shooting with most of the time...  This is a real icc profile you can apply to the image, not just the simple set of camera corrections you create in ACR or LR and apply during conversion.  And be forewarned that unlike paper or monitor profiles, camera profiles can be a *bitch* to get just right and usually require significant time spent editing the profile for optimal results...

Cheers,

Could you please explain how an input profile would help - or more generally, what exactly it does? I have heard people talk about input profiles (beyond the simple camera corrections) but they never made sense to me. As I understand profiles (printer and monitor), their job is to specify how the digital "colors" (numbers) in a digital image are translated to physical colors on the monitor or print. I assume that aq camera profile would come into play when the RAW image is processed, but seeing as there are no physical colors involved I don;t see what exactly it does.

THanks,

Peter
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Peter
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Jack Flesher
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« Reply #3 on: July 09, 2009, 09:20:40 AM »
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It does the exact same thing for your camera as it does for the monitor or paper.  It tells the camera how the physical colors of the *subject* get accurately translated by the camera into those digital numbers, so that what comes out of the camera to be sent downstream is already "accurate".  Now when you send that to your profiled monitor for viewing, you will be seeing what the actual subject looked like, not the camera maker's interpretation of what it should look like.  Here you get to edit it to match *your* tastes whether accurate or artsy -- and the "art" is to make the digital 2-D final look more like a 3-D original (~~ an oil painting has depth to the brush strokes, a watercolor texture to the paper).
« Last Edit: July 09, 2009, 09:26:24 AM by Jack Flesher » Logged

Colorwave
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« Reply #4 on: July 09, 2009, 12:39:05 PM »
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Have you tried Adobe's free DNG Profile Editor?  The automated process still has the limitations of the 24 patch Colorchecker, but it does a good job creating a starting point, and affords the possibility of fine tuning on top of that foundation.
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ormike
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« Reply #5 on: July 09, 2009, 01:49:39 PM »
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Quote from: Colorwave
Have you tried Adobe's free DNG Profile Editor?  The automated process still has the limitations of the 24 patch Colorchecker, but it does a good job creating a starting point, and affords the possibility of fine tuning on top of that foundation.
I must admit I have not done much with this editor.
I worked with it a little and then shied away because it did not allow numerical input after the fact for editing.
It seem that the DNG Editor is more for "Pleasing Color"  than color accuracy but I may be wrong.

I would like to boil down my original post into the question;

Which Color Targets and Profiling Software combinations have proved to be effective in achieving Accurate Color reproduction with Digital Cameras?

Thanks,

Mike
« Last Edit: July 09, 2009, 01:52:12 PM by ormike » Logged
tho_mas
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« Reply #6 on: July 09, 2009, 02:48:44 PM »
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Quote from: ormike
Which Color Targets and Profiling Software combinations have proved to be effective in achieving Accurate Color reproduction with Digital Cameras?
http://www.basiccolor.de/english/Datenblae...t_E/input_E.htm
(homepage: http://www.basiccolor.de/english/index_E.htm )
« Last Edit: July 09, 2009, 02:49:18 PM by tho_mas » Logged
jackbingham
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« Reply #7 on: July 10, 2009, 05:15:52 AM »
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You know, I happen to be a big fan of camera profiles, but something you said ever so casually caught my attention. " under consistent studio lighting" Can you tell me what this means? Are you using Strobes? Are the tubes all brand new. Are you using softboxes? Are these the same age?
Lighting is probably the most critical part of this equation. There is no solution better than using tungsten lights and dimmers. Strobes, no matter how good will never be a critical color match to one another. The only way to really nail this is with dimmers and a color meter. Once you match the lights you are much further down the road.
As for camera profiling, I obviously am partial to Coloreyes but two things are true no matter what you choose. A 24 patch color checker is way to small a data set and secondly unless it is a glossy target you won't have near the tonal range you need.
All that being said you will never find a solution that solves all the problems here. There will be paint colors you just can't hit and for that matter can't print. Camera profiling and critical lighting will get you dramatic time savings regardless.
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Jack Bingham
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ormike
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« Reply #8 on: July 10, 2009, 06:28:07 AM »
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Quote from: jackbingham
You know, I happen to be a big fan of camera profiles, but something you said ever so casually caught my attention. " under consistent studio lighting" Can you tell me what this means? Are you using Strobes? Are the tubes all brand new. Are you using softboxes? Are these the same age?
Lighting is probably the most critical part of this equation. There is no solution better than using tungsten lights and dimmers. Strobes, no matter how good will never be a critical color match to one another. The only way to really nail this is with dimmers and a color meter. Once you match the lights you are much further down the road.
As for camera profiling, I obviously am partial to Coloreyes but two things are true no matter what you choose. A 24 patch color checker is way to small a data set and secondly unless it is a glossy target you won't have near the tonal range you need.
All that being said you will never find a solution that solves all the problems here. There will be paint colors you just can't hit and for that matter can't print. Camera profiling and critical lighting will get you dramatic time savings regardless.
Thanks Jack,
Like I said in the original post I am not a photographer by trade so the subject of lighting is as much of a challenge as learning about f-stops, ISO settings and Aperture Priority. When film transparencies became difficult to come by I chose to buy the 5D and the journey began.
When I said "under consistent studio lighting" I meant that I was shooting in the same environment. I have used tungsten with polarized filters (work-lights from Home Depot), banks of fluorescent tubes and now I am working with four Eiko EBW 500 watt daylight incandescent bulbs because I like the idea of the illuminate being as close to 5000K as possible.
Because everything you say about paint colors/pigments is true I have been shooting the Color Checker with each piece of Art and building a new profile for that shot at that time on that day.
To judge the accuracy of the profile I print the Color Checker and read the Lab numbers of the print vs. the Lab numbers of the original Color Checker and when I get some of the patches at delta E of > 20 I know something is not working right.
I agree that the 24 patches on the Color Checker is just not enough and this is why I am looking for a better target and it may well be Coloreyes. Awhile back I spoke with Derrick at Integrated Color and he stressed the importance of the lighting being even over the original art so after struggling with that for awhile I found EquaLight 2 which seems to work exceptionally well.
Again, thank you for your comments and I'll be in touch.
« Last Edit: July 10, 2009, 06:31:07 AM by ormike » Logged
digitaldog
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« Reply #9 on: July 10, 2009, 07:42:38 AM »
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Quote from: ormike
Because everything you say about paint colors/pigments is true I have been shooting the Color Checker with each piece of Art and building a new profile for that shot at that time on that day.
To judge the accuracy of the profile I print the Color Checker and read the Lab numbers of the print vs. the Lab numbers of the original Color Checker and when I get some of the patches at delta E of > 20 I know something is not working right.

That's not going to work. It doesn't tell you about the process correctly. With a product like ColorThink, you could produce the detlaE's of just the output profile, that tells you nothing about the rest of the process. You can use that product to tell you the expected and produced Lab going through the profile, that's useful for gauging the BtoA and AtoB tables in a profile. The goal for "accurate" color can't begin until you define accurate. That's not a path where the Lab values of a Macbeth in a scene are produced by measuring the Lab values of the print. Not even close. Start here:
http://www.color.org/ICC_white_paper_20_Di...ment_basics.pdf

Got nothing to do with the number of patches on the Macbeth at this point (and yes, the DNG profile editor even with those few patches can help you produce pleasing color).
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Andrew Rodney
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Jack Flesher
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« Reply #10 on: July 10, 2009, 08:51:47 AM »
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Quote from: jackbingham
There is no solution better than using tungsten lights and dimmers.

If I did art repro for a living, I'd invest in a set of NorthLights:  http://www.northlightproducts.com/html/copy_lights.html

However for any given copy set -- the same heads at the same distance with the same modifiers and same power settings -- the newer digital strobe packs are *very* uniform in their output, and even if you need to adjust output by one or two two stops, remain within an acceptable margin IMO.  Strobe tubes will change with age however, and more so initially, so frankly it is better to start with a used set of heads.

Any way you slice it, it is a lot of work at the front end, and all you can do is get reasonably close, not perfect...

Cheers,
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Kumar
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« Reply #11 on: July 11, 2009, 06:27:23 AM »
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There's a lot of information here: http://www.fho-emden.de/~hoffmann/howww41a.html
This pdf explains camera calibration for reproduction: http://www.fho-emden.de/~hoffmann/camcal17122006.pdf

Cheers,
Kumar
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jackbingham
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« Reply #12 on: July 11, 2009, 09:42:10 AM »
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Sorry, not even close. If we were talking about film I would agree. But having done extensive testing in this particular arena I can say without a doubt that tungstens with dimmers is the only good choice. Digital cameras have a sensitivity way beyond film and even the newest strobes are not close enough. And nylon on softboxes, no way.

As for the process of profiling you want to nail down your lighting and then make one profile. This making a profile for every shot is worthless.
If you are looking for numerical accuracy you will be spending a lot of time beating your head against concrete. Pleasing is more likely what your customer will respond too. And from my experience having built a macbeth based product and a large target product, and done extensive testing, and customer jobs on artwork and commercial color critical products, there is no comparison. Big target always wins.
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Jack Bingham
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Jonathan Ratzlaff
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« Reply #13 on: July 11, 2009, 11:58:48 AM »
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"Tungsten with dimmers is the only good choice"
Consider the composition of the sensor, with twice as many green sensors as red or blue.  So one would think that the sensor would be optimally configured for green light.  Look at a light curve for a 5500 light source.  The peak is in the green section.  Look at the peak of a tungsten light source, red.  Why do you think most digital cameras  have trouble with subjects under tungsten light?  So for accurate colour, you need a hotter light source.  Unless you are using a colourmeter, how are you going to ensure that a tungsten light with a dimmer is operating at the proper colour temperature and how are you going to make sure it is consistent because as the voltage to the lamp changes so does the colour temperature.
You need a light source that produces a consistent colour temperature that is independent of voltage and higher than that produced by tungsten lighting for the best colour rendition.
The original poster was using tungsten halogen worklights with polarizing filters.  He would be much better off getting some strobes and using them.  He is going to get much less fluctuation than he will with the worklights and colour much more compatible with the sensor in the camera


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jackbingham
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« Reply #14 on: July 11, 2009, 02:50:35 PM »
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Digital cameras have no trouble with tungsten light. Gray balance is a far better tool then you suggest. And yes you need a color meter to match tungsten lights. Strobes do not and never have produced consistent color temperature to the degree required for this kind of copywork. If I had not done a lot of this I would not bother with this any further but I've done the testing with countless photography clients and my own customers. Tungsten with dimmers is better unless power fluctuates at a given location. Camera profiling is a waste of time unless you can match the light color across the painting.
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Jack Bingham
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Colorwave
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« Reply #15 on: July 11, 2009, 04:35:18 PM »
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Jack-

I noticed on your site that you say you do not recommend using ACR or Lightroom because they do not allow the use of camera profiles.  Is this still accurate for your profiling package with the current releases of those two applications, or was this for previous versions?  What about Capture One?  No issue there, I assume?  Adobe obviously now allows the use of camera profiles, but has an odd implementation that must recognize that the profile is appropriate, and only allows for a limited number of user selected options when it comes to profiles.  Do they let ColorEyes profiles (for a Phase One back, in my case) past their gatekeeper?

I use Profoto strobes with large softboxes when I can make the reflections work (shiny, highly textured canvas can be tricky, even when the boxes are flagged off) and use extremely diffused natural light otherwise.  Are you saying that you have found that strobes and two layers of fresh white diffusion on softboxes still produce color variance across a scene?  I normally use a light meter, but not a color meter, although I have borrowed a friend's color meter and did not read any color shifts with my setup.  Obviously, some strobes are better than others.  Profoto is one of the better brands, but probably not on par with Briese (or Bron?) for consistency.  I observed a slight color temperature change when I reduced the power of the strobes significantly, but that was more of an FYI experiment.  I don't really mess with strobe power for art reproduction.  My guess is that my need for individualized color correction is far more driven by the size of the ColorChecker color sample in profiling than variance in lighting, although I wouldn't swear it isn't possible to be some of the latter.

What tungsten source do you use?  HMI?
« Last Edit: July 11, 2009, 04:36:24 PM by Colorwave » Logged

digitaldog
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« Reply #16 on: July 11, 2009, 05:08:20 PM »
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Quote from: Colorwave
Jack-

I noticed on your site that you say you do not recommend using ACR or Lightroom because they do not allow the use of camera profiles.

Sure they do! Just not profiles Jack's product can build (well he could if he wanted to).

Seems an odd reason to dismiss two such products outright.

http://labs.adobe.com/wiki/index.php/DNG_Profiles
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Andrew Rodney
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tho_mas
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« Reply #17 on: July 11, 2009, 05:41:22 PM »
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Quote from: digitaldog
Sure they do!
They do NOT work with icc profiles as input profiles and you can't process the tif in those icc profiles!
That's what "colorwave" ask for and the answer is: no.

Quote from: Colorwave
Do they let ColorEyes profiles (for a Phase One back, in my case) past their gatekeeper?



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digitaldog
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« Reply #18 on: July 11, 2009, 05:55:34 PM »
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Quote from: tho_mas
They do NOT work with icc profiles as input profiles and you can't process the tif in those icc profiles!
That's what "colorwave" ask for and the answer is: no.

They allow the use of camera profiles which is what's quoted above. No, they don't allow the use if ICC camera profiles. But they of course do allow the use of custom profiles. That the product mentioned doesn't support DNG profiles in no way invalidates this approach to producing a camera profile.

Quote
I noticed on your site that you say you do not recommend using ACR or Lightroom because they do not allow the use of camera profiles

So this then begs the question, why as Colorwave asks does this web site not recommend ACR or LR? Seems pretty obvious to me.

Quote from: jackbingham
You know, I happen to be a big fan of camera profiles...

I guess just ICC camera profiles...
« Last Edit: July 11, 2009, 05:58:46 PM by digitaldog » Logged

Andrew Rodney
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tho_mas
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« Reply #19 on: July 11, 2009, 06:08:46 PM »
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Quote from: digitaldog
They allow the use of camera profiles which is what's quoted above. No, they don't allow the use if ICC camera profiles. But they of course do allow the use of custom profiles.
the "profiles" you are talking about are actually just a set of internal adjustments. Begs the question if the term "profile" makes sense here.
In any case you can't process the TIFs from ACR/LR without conversion to another profile but instead just embed the camera profile (as you can do it in Capture One).
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