ACR Calibrator for ACR 4.1

Greetings,

I assume that version is cs3 as it refers to ACR 4.1, would that be right/

http://http://www.fors.net/chromoholics/index.php

Georg Baumann said:

I assume that version is cs3 as it refers to ACR 4.1, would that be right

Click to expand...

Correct, CS3 and earlier.

Bart

Kewl...Thank you Bart! I am getting slowly closer to the world of scripts. <smile>

I was wondering, how are you guys using these calibrations? I don't mean technically, I understand that.

It has been claimed that these ACR calibrations are really only useful in the same environment as the target was photographed in. I don't have enough theoretical knowledge to confirm or dismiss this statement. However, I have read that it is true but that if the target is photographed differently than how you are instructed, they can certainly be used in most situations. Actually, that's bending the truth a bit, because the statement did not apply to the ACR calibrator and the ColorChecker but rather "normal' camera calibrations. The statement comes from the guys at Integrated Color and they claim the following:

By eliminating as many variables as possible while shooting the target, then a profile can be built that would be useful across the board. So instead of using two stobes, they use one, for example. They shoot it in a controlled environment with very little to no color casting surfaces nearby.

Now, the interesting part is how this can be done to a large extent without all the fussing about with grey cutouts and walls and whathaveyou. Their tip is to photograph the target outside, at night, in the dark, using a single flash.

All this was discussed in the context of their own product ColorEyes Camera, but I was wondering if using the same methodology for shooting the ColorChecker for ACR would be beneficial, and if doing so would produce an ACR calibration that could be used for most in not all lighting conditions.

Hi Kris,

Interesting points, I think I will try to invite Thomas here to see what his thoughts are.

This calibration isn't resulting in a camera-calibration like one could do with C1, but rather a finetuning of the generic, aka Thomas Knoll's profile. As it's calibrating the 3 primairy colors only, it's not overprecise.

The advantage: you can do it yourself, even when shooting in nasty light conditions, as night street light, and run a calibration first, for applying it later.

Still best you shoot your target in different light situations, as flashlight, day-sun, day-clouds.

Michael Fontana said:

This calibration isn't resulting in a camera-calibration like one could do with C1, but rather a finetuning of the generic, aka Thomas Knoll's profile. As it's calibrating the 3 primairy colors only, it's not overprecise.

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Exactly, that is what I meant by "normal" camera calibration.

Michael Fontana said:

The advantage: you can do it yourself, even when shooting in nasty light conditions, as night street light, and run a calibration first, for applying it later.

Still best you shoot your target in different light situations, as flashlight, day-sun, day-clouds.

Click to expand...

Yes, but I'm too lazy for that I don't even use the WhiBal even though I know its great for the gray balance. So bringing my ColorChecker everywhere and shoot that beforehand is never going to happen. I will not even shot a fixed number of them and then apply them in LR/ACR. However, if I can have one that I can apply to all images, then I can jump through quite a few hoops to get that single calibration.


I remembered where I "read" this. It was in this video at LL:

http://luminous-landscape.com/reviews/accessories/coloreyes-commercial.shtml

P.S. When I say apply to all images, I obviously mean apply to all images from that camera.

KrisCarnmarker said:

...Yes, but I'm too lazy for that I don't even use the WhiBal even though I know its great for the gray balance. So bringing my ColorChecker everywhere and shoot that beforehand is never going to happen. I will not even shot a fixed number of them and then apply them in LR/ACR. However, if I can have one that I can apply to all images, then I can jump through quite a few hoops to get that single calibration...

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Agree entirely. I've bought a 24-color GM checker a few weeks ago. I will calibrate my 5D and see what it is worth as a generic tool (ie one generic profile for all shooting situations). Will report back when I get this done.

Cheers,

I'll be interested to hear of your results, Cem. It's something I may well do myself at some time.

Regards,
Murray

Michael Fontana said:

This calibration isn't resulting in a camera-calibration like one could do with C1, but rather a finetuning of the generic, aka Thomas Knoll's profile. As it's calibrating the 3 primairy colors only, it's not overprecise.

Click to expand...

Correct. With these ColorChecker based scripts one doesn't create a camera profile (which requires many more color patches to even get close), but one tunes the specific camera colorspace to the Thomas Knoll camera characterization in ACR.
ACR itself will still adapt its color rendering to Tungsten or Daylight types of illuminants, but with a more accurate Daylight baseline.

The advantage: you can do it yourself, even when shooting in nasty light conditions, as night street light, and run a calibration first, for applying it later.

Click to expand...

It remains to be seen if an additional Tungsten calibration with a Colorchecker will add more than a simple Whitebalancing on a suitable grey or white object will do.

Bart

KrisCarnmarker said:

Yes, but I'm too lazy for that I don't even use the WhiBal even though I know its great for the gray balance.

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That's not lazy, that's massochistic conduct. It'll take more time to do after the fact, if at all possible to nail the whitebalance.

So bringing my ColorChecker everywhere and shoot that beforehand is never going to happen.

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You'd probably wear out the target before long, as it is a delicate thing. I'm sceptical (but willing to be convinced otherwise) whether it would substantially improve color accuracy in Photoshop.

However, if I can have one that I can apply to all images, then I can jump through quite a few hoops to get that single calibration.

Click to expand...

That's the idea, and it can be set as the camera default. ACR will thus adjust the baseline for each camera that had such a calibration done and saved.

Bart

Bart_van_der_Wolf said:

..................
It remains to be seen if an additional Tungsten calibration with a Colorchecker will add more than a simple Whitebalancing on a suitable grey or white object will do.

Bart

Click to expand...

Hi Bart

it's a question of the light source's spectrum not the WB and tint.
Basically this means: The more different the spectrum xy is - compared to the dailight's - the more a ACR/LRcalibration makes sense.

Here some calibrations, just beeing day 5'000 and tungstene (conventional bulb, not halogen):

Sun, temp 5'000 K:

Shadow Tint: -1
Red Hue: -19
Red Sat: 25
Green Hue: -11
Green Sat: -7
Blue Hue: 5
Blue Sat: -4

Tungesten 2710 K

Shadow Tint: 0
Red Hue: -14
Red Sat: 16
Green Hue: -35
Green Sat: 29
Blue Hue: 8
Blue Sat: -15

BTW: ACR/LR-cals are good too, if someone is using different brands of lenses, as they have different color "shifts" as well. The difference is not extrem, but noticable.

BTW2: I often add the MBeth colorchecker to delicate paintings reproductions. As the RGB-values of it are known, --> Chris Murphy, its a big help for the prepres people.

I thought I'd share my ACR daylight calibrations for the 5D, 1DMkIIN and 1DMkIII.

These were all shot under midday sun (~5000k) over a couple of days using EF 24-70f2.8 and EF 70-200f2.8 lenses. The LR template files are available for download.

I found that these two lenses have almost identical colour charateristics and so using numerous images from each lens / camera combination, tweaking the output and iteratively running Rag's scripts, I have some confidence that what I shoot with either of three cameras is realtively colour consistent.

As a side note, I found that the 5D and 1DMkIII ACR adjustments were very similar, whereas the 1DMkIIN needed more green adjustment.

BTW, Thanks to Bart for giving me some advice based on his findings!

John_Nevill said:

I thought I'd share my ACR daylight calibrations ...

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Thanks, I'm sure they will be useful starting points for others. I do want to stress that I'd consider them as starting points though.

Rags Gardener's scripts also includes a script to visually compare the resulting ColorChecker image with the goal colors used while calibrating. That script will probably show that additional visual improvements can be made by adjusting the HSL-Luminosity values, in addition to the camera calibration. In the case of the EOS-1Ds Mark II and EOS-20D that I calibrated (although using an older version of the script), especially (but not exclusively) the luminosity of the red channel needed to be lowered several notches. While that will impact the overall colorimetric delta-E metric, the visual result is much improved, also in a direct comparison with the ColorChecker itself.

As a side note, I found that the 5D and 1DMkIII ACR adjustments were very similar, whereas the 1DMkIIN needed more green adjustment.

Click to expand...

I've also read from other users of these calibration scripts, that the intra-model variation is apparently pretty small, which makes sharing this information even more useful.

Bart

Thanks! Where do the templates get stored on a PC?

--John

John Hollenberg said:

Thanks! Where do the templates get stored on a PC?

--John

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They get held in the User/AppData/Adobe/Lightroom/Develop Prests/User Presets/ folder.

Easiest way is to open up LR, go to the Dev module, under presets, right click and add a new folder. Right click the new folder (user presets) and import the .LRtemplates (one at a time).

Thanks. Will try out the 5D calibration. It's bound to improve the reds!!!

--John

Bart_van_der_Wolf said:

In the case of the EOS-1Ds Mark II and EOS-20D that I calibrated (although using an older version of the script), especially (but not exclusively) the luminosity of the red channel needed to be lowered several notches. While that will impact the overall colorimetric delta-E metric, the visual result is much improved, also in a direct comparison with the ColorChecker itself.

Click to expand...

I agree, I found (asthetically) that the red needs -4 and the blue +3 on the luminosity tab, although this throws the purples out, so I leave them as-is and use a new preset depending upon image colour content.