AcrCalibrator Google Group

Re: [acrcal] Using AcrCalibrator with complete scene

st...@sprengels.com (Steve Sprengel) — Sat, 09 Aug 2008 18:18:56 UT

You can, but the concern is that it would be too small for the measurements of the color patches to be very accurate. There is some slight variation from one pixel to the next in an image and the script samples a reasonably small area of each CC path to make its judgments so you might get a different calibration depending on the exact placement of the corner-patch pen on a particular run. You can test your theory by doing a calibration from such a shot, then doing two or three more while moving the corner-patch pen-marks in a different area of the corner patches. The sample area is about 1/5th of the width of each square so don't get too close to the edge with the pen, but you can move it probably move it around in the middle third of each square.

Re: [acrcal] Re: ACR Calibrator Problems

st...@sprengels.com (Steve Sprengel) — Sat, 09 Aug 2008 17:45:47 UT

If you are talking about the recently obsolete Fors' script: The numbers are the calibration and would be different for each model of camera, and can be entirely different for different camera models, quite a bit different for each white-balance situation, a little different from different cameras of the same model, and even slightly different from one run of the script to the next due to pen-placement differences.

Using AcrCalibrator with complete scene

daniele.c...@gmail.com (Daniele Cogo) — Sat, 09 Aug 2008 11:38:29 UT

Hello, I'm Daniele Cogo, an italian graphic design.

This is my question: can I use the AcrCalibrator with a photo having
both the object and the ColorChecker?
Something like this:
[link]

Daniele

Re: ACR Calibrator Problems

j.auchinl...@hotmail.co.uk (kermit) — Wed, 06 Aug 2008 09:57:42 UT

Many thanks for the link - have got it all working.

One observation though... The lecturer gave out a list of numbers -
and the numbers generated are not even close to those on the sheet.
Is this a problem witht he camera or what?

Kermit

Re: [acrcal] Re: ACR Calibrator Problems

st...@sprengels.com (Steve Sprengel) — Mon, 04 Aug 2008 06:30:45 UT

There is a video, somewhere, that tells the user to select the corners in an X shape, but it should be a U shape: top-left, bottom-left, bottom-right, top-right. Perhaps you're doing that, or maybe you are selecting the very edges of the squares instead of the centers.

HOWEVER, if you have CS3, with the release of ACR 4.5 and LR2.0 last week, you can use the new Adobe Labs DNG Profile Editor to create a custom Camera Profile that you select in place of the ACR 4.4 that you see in ACR and LR, now.

Re: ACR Calibrator Problems

j.auchinl...@hotmail.co.uk (kermit) — Mon, 04 Aug 2008 06:14:51 UT

Hi I'm new to the forum. Instead of clogging things up with another
thread I thought I'd add to this one as it is similar to the op - I
hope people do not mind.

I'm attempting to calibrate my D80 using the script. I have followed
the instructions on this site and watched the video on Martin Evenings

Re: DNG Profile Editor

mvo...@gmail.com (MacUser) — Thu, 31 Jul 2008 11:16:51 UT

Hello Thomas,

Thanks for the info and the workflow.

The DNG Profile Editor worked fine and very fast although it is picky
on te input.
I had to shoot several new test images because my old ones where "over
exposed".
The new ones where also over exposed and when I I got that right they
had a "color cast".

Re: Camera RAW settings (brightness, contrast, tone-curve)

markus.bro...@gmail.com (Markus) — Thu, 31 Jul 2008 09:58:35 UT

Dear Steve

Thanks for this information - so nothing wrong in the way I test the
results ;)
I would have expected the default ACR settings are a bit more
"normalised", but apparently arn't.

Re: [acrcal] Re: Camera RAW settings (brightness, contrast, tone-curve)

st...@sprengels.com (Steve Sprengel) — Wed, 30 Jul 2008 16:08:05 UT

The differences in color-accuracy you are seeing are what is to be expected.

A photometrically accurate photo is not the most pleasing photo, and the default ACR settings--which are intended to give a pleasing photo, have increased contrast and a non-linear toning curve which has the side-effect of increased saturation, so the color-error should be more for a "pleasing" version.

Re: [acrcal] Re: DNG Profile Editor

st...@sprengels.com (Steve Sprengel) — Wed, 30 Jul 2008 15:54:18 UT

To check the accuracy of your raw conversions you can use a script from Rags-Gardner against any one of a number of color targets:
[link]

Presumably you are using the color-checker for the calibration so Read_Colors_CC24.jsx would be the script to use; however, if you have any of the other color-targets listed, you can validate against shots of those as well.

Re: Camera RAW settings (brightness, contrast, tone-curve)

markus.bro...@gmail.com (Markus) — Wed, 30 Jul 2008 09:44:28 UT

PS: I am aware that ProfileEditor only cares about color, not
luminance. Therefore I also report the DEColor values here, which are
more informative than the DE2000 in that respect.

DEColor (default settings): ~3
DEColor (brightness=0,Contrast=-10, Tone-Curve=linear, saturationto=
+10): ~1.5

Camera RAW settings (brightness, contrast, tone-curve)

markus.bro...@gmail.com (Markus) — Wed, 30 Jul 2008 09:34:42 UT

I played a bit with the Profile Editor but have some issues validating
the obtained profile.

After I did the calibration which was finished in about a second
(impressive), I exported the profile and applied it to the DNG in
Camera RAW (16bit, ProPhotoRGB). Now, using a Photoshop script such as

Re: DNG Profile Editor

ws....@lam.ws (Hermit) — Wed, 30 Jul 2008 08:49:13 UT

I have been trying out the DNG Profile Editor for a while. The editor
is indeed a real time save as it takes NO time to calibrate the
colorchecker. What is even cooler is that it allows you to embed dual
lighting (6500k and 2850k) into one profile.

However, it is not without issues. For example, I ran into a problem

Re: [acrcal] Re: DNG Profile Editor

st...@sprengels.com (Steve Sprengel) — Wed, 30 Jul 2008 02:17:38 UT

IT8's can be cheaper than the color-checker. They have a glossy finish and are used for scanner calibration so aren't ideal for camera calibration but I'm sure they can work if you are careful to keep environmental reflections to a minimum and relatively neutral colored.

My IT8 came along with a $70 printer/camera/scanner ICC-profile creation program called ProfilePrism from [link] which also included the specific reference file, so I can use it with other programs, such as Imatest, which I use to measure the color-accuracy of my camera profiles. [link]

Re: [acrcal] Re: DNG Profile Editor

shaocahol...@gmail.com (Shao Zhang) — Wed, 30 Jul 2008 01:04:33 UT

How much more expensive are good IT8 targets compared to the chart
AcrCalibrator uses?