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Author Topic: Shooting Color Targets  (Read 8691 times)
Hening Bettermann
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« on: February 12, 2013, 02:06:34 PM »
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Hi

When shooting the ColorChecker or QPcard, I have hitherto always tried to fill the frame.
Now, preparing to use the ColorPerfect plug-in, I read
"Also, do not make the grayscale fill the frame – leave some room at the edges (technically, this avoids most of the cosine to the fourth power falloff effect)."
(http://www.c-f-systems.com/DunthornCalibration.html)

Reading this, I vaguely remember a recommendation that the target should fill about 1/3 of the frame (in one direction, I assume), I don't remember the source. This seemed rather little to me, so I have ignored it.

So how much of the frame should the target fill?

Another recommendation is (for color targets) to defocus slightly - just how much is "slightly"?

Thank you for your advice - Hening.
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Vladimirovich
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« Reply #1 on: February 12, 2013, 02:58:40 PM »
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Hi

When shooting the ColorChecker or QPcard, I have hitherto always tried to fill the frame.

don't... vignetting (from lens to sensor) will ruin your profile unless you succumb to placebo effect (even if a particular profile building software - like QPCard is alleged to - is using white background between tiles to adjust the exposure to fix it)
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bill t.
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« Reply #2 on: February 12, 2013, 07:47:15 PM »
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I believe the Passport software needs to be able to find the four small "^" corner marks around the classic, 24 patch array.  That matches my experience.  Focus is as important as size.  And of course texture from noise needs to not be overly large relative to patch size.  And BTW the deep shadows in the black Passport hinges are very useful as an RGB 0 reference, which is something the QP Card doesn't offer.
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Vladimirovich
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« Reply #3 on: February 12, 2013, 10:59:32 PM »
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And BTW the deep shadows in the black Passport hinges are very useful as an RGB 0 reference, which is something the QP Card doesn't offer.
why do you need that for dcp profile building ?
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bill t.
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« Reply #4 on: February 13, 2013, 12:37:24 AM »
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No, but if you're using the Passport on a scene by scene basis in a production situation, it's handy.
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digitaldog
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« Reply #5 on: February 13, 2013, 09:20:51 AM »
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No, but if you're using the Passport on a scene by scene basis in a production situation, it's handy.

As are the off white patches for WB (season to taste) in the raw converter. Nothing to do with building a profile but very handy to have in the target itself.
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Andrew Rodney
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Hening Bettermann
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« Reply #6 on: February 13, 2013, 12:32:22 PM »
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Thanks to all of you who replied - however, I still don't know just how much of the frame the target should fill, and just how much it should be de-focussed.
Kind regards - Hening.
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Redcrown
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« Reply #7 on: February 13, 2013, 01:03:40 PM »
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I've shot dozens of images of my full-sized colorchecker chart with a Canon 5D2. Different lenses, different frame-fill, different focus, different exposure, different light.

Processed these with Adobe DNG Profile editor. The resulting profiles show very little differences, so little to be insignificant. Just try it yourself. Shoot the target at at different frame-fills and different focus, make several profiles and see if you can tell a difference.

So, within reason, I don't think it makes much difference. Of course, if you shoot the target with a ultra wide angle lens that suffers significant vignetting and distortion, and you grossly over or under expose, and you use some wierd uneven light, then the garbage in, garbage out rule may apply.

For me, the main benefit from making custom profiles is in using different base tone curves.
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digitaldog
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« Reply #8 on: February 13, 2013, 01:06:10 PM »
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Unlike shooting targets for an ICC camera profile (ugh) the shooting of the Passport or Macbeth is very forgiving when making a DNG profile.
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Andrew Rodney
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Hening Bettermann
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« Reply #9 on: February 13, 2013, 02:37:34 PM »
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Thanks again. Sorry I forgot to specify that I make ICC profiles. They have worked well even with the CC filling the frame, but I am starting on a new round with my workflow, and any possible improvements should be implemented now.
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Vladimirovich
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« Reply #10 on: February 13, 2013, 03:45:32 PM »
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For me, the main benefit from making custom profiles is in using different base tone curves.
but you do not need to shoot targets to create different base tone curves
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Vladimirovich
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« Reply #11 on: February 13, 2013, 03:48:48 PM »
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Thanks again. Sorry I forgot to specify that I make ICC profiles. They have worked well even with the CC filling the frame, but I am starting on a new round with my workflow, and any possible improvements should be implemented now.


and if ICC then what is your raw converter ?
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Hening Bettermann
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« Reply #12 on: February 13, 2013, 04:17:45 PM »
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Iridient Developer, formerly Raw Developer.
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Rhossydd
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« Reply #13 on: February 14, 2013, 02:22:52 AM »
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I still don't know just how much of the frame the target should fill, and just how much it should be de-focussed.
I doubt that there's a single default answer.
There's obviously a need to ensure lighting is even across the chart and that any lens problems (vignetting/major CA etc) are excluded.
Beyond that why not ask the authors of the software you're using to create the profile ? Once you know that you'll be able to work out how to shoot it.
I'd guess there's a requirement for a minimum patch size to sample from the frame. If that's correct, different capture resolutions will define the minimum size the target can be within the shot, so the chart could be small in frame in a 5Dii, but much larger on a 10D.

The smallest size of patch I've successfully built a profile from had patches 60px square with Adobe DNG profiler editor, but it might work on even smaller sizes too. That was pretty small in frame, but the software worked OK.
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Hening Bettermann
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« Reply #14 on: February 14, 2013, 08:39:24 AM »
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The software I use to build ICC profiles is Argyll CMS. The instruction for this says that the frame of the target must be visible.
So all in all it does not seem to be very critical. With regard to the defocussing, I think I proceed as I am used to: put a gray card in front of the target to check evenness of illumination, focus on the frame of that card, then remove it without re-focussing.

Thanks to all of you!
« Last Edit: February 19, 2013, 12:49:05 PM by Hening Bettermann » Logged

Vladimirovich
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« Reply #15 on: February 14, 2013, 11:27:17 AM »
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So all in all it does not seem to be very critical.

if you will read Iliah Borg (who creates profiles for RPP) you will find out that that it is  Cheesy ...
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digitaldog
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« Reply #16 on: February 14, 2013, 11:32:22 AM »
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Iridient Developer, formerly Raw Developer.

I wrote to the author who said it does support DNG profiles (I have to test this out and see the full implications). Of course it also supports ICC camera profiles too.
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Andrew Rodney
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Hening Bettermann
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« Reply #17 on: February 14, 2013, 12:35:48 PM »
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> if you will read Iliah Borg (who creates profiles for RPP) you will find out that that it is   ...

So maybe that was the source where I snapped up that 1/3 figure? I'll check.
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Hening Bettermann
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« Reply #18 on: February 14, 2013, 12:40:02 PM »
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> I wrote to the author who said it does support DNG profiles

Oops! That must be of lately, I did not check that. Thanks Andrew.
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Hening Bettermann
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« Reply #19 on: February 14, 2013, 01:12:56 PM »
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> if you will read Iliah Borg (who creates profiles for RPP) you will find out that that it is   ...

I can't find anything in that way on the RPP web site. Would you have a link?
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