Camera Calibration in ACR

[Dinarius]

First off, I'm not sure if my question should be posted here or in Color Management. But, here goes.........

I've made profiles for my 1Ds Mklll using the Bruce Fraser method outlined here>

http://www.creativepro.com/article/out-gam...p-cs?page=0%2C1

I've incorporated a few tweaks which I found here>

http://people.csail.mit.edu/ericchan/dp/acr/

......the most useful one being to set the Point graph in the Tone Curve tab from its default (Medium Contrats) to Linear. This greatly assists the first stage of the process, namely, setting the grey patch values to match the test values.

I've also added one of my own which is to include a basICColor grey card (which is totally neutral) in the shot rather than make a colour balance by clicking on one of the Gretag patches.

I have no problems matching the grey patches to my desired levels - Adobe 1998 equivalents in my case.

Once this is done, the red, green and blue patches are already in the ballpark.

However, one thing that bothers me is Fraser's suggestion that before proceeding to the correction of the colour patches themselves (now using the HSL tab - which allows me to get the patches bang on - and not the Camera Calibration Tab) he says that the green value of the green patch should be made to equal the aim value using the Saturation Slider.

In Adobe 1998 16 bit, the desired value of the green patch is 101, 148, 78. After adjusting the grey patches (but before any adjustments in the HSL tab) the green patch values are 101, 145, 85 - pretty close to what I'm aiming for.

Increasing the green value from 145 to 148 requires moving the saturation slider a full +16 points. This has a great effect on the entire Gretag chart, including patches I can't adjust.

Obviously, the proof of the pudding is in the eating. I'm just wondering if others use this step too?

Thanks.

D.

One last thing.........there are eight sliders in the HSL tab. I like to use all of them. Red, Green, Blue, Yellow, Orange (R2, P1), Purple (R2, P4), Magenta (R3, P5) are obvious (I think!   ) But, which patch should I use for Aquas? R1, P6? R3, P6?

[Schewe]

I've made profiles for my 1Ds Mklll using the Bruce Fraser method outlined here>

Really, you should prolly forget doing this the old fashioned way and download the Adobe DNG Profile Editor. You will get far more accurate results and have the ability to fine-tune colors to a degree you can't in the Calibration panel of Camera Raw.

[Dinarius]

Jeff,

Thanks for the reply.

So, I download the DNG Converter (I'm Vista x64) and convert the shot of the Gretag CC to .dng.

In ACR, the RGB reading of the red patch (before any adjustments) is 196, 54, 59.

In the Profile Editor, the RGB of the same file and same red patch is 55, 20, 11.  

Also, if I make an adjustment (e.g. if I reduce the luminance of the red patch) the patch darkens, but the RGB reading remains the same!

What is going on here?

This looks like a fantastic tool since I will be able to adjust all 18 colour patches, but all the RGB readings are very, very weird!

Any idea?

Thanks.

D.

ps. I've read a few tutorials about generating a profile using this tool. None of them mentions first adjusting the grey patches (which can't be done in the Profile Editor, so I presume this would have to be done in ACR first and then you would have to choose Apply Camera RAW Adjustments in the Profile Editor's Options menu) which one surely must do in order to keep the over luminance of the patches in the ballpark before adjusting them? A kind of Fraser method, but using a more sophisticated HSL adjustment?

Anyway, can do nothing until I sort out those readings.

[Peter_DL]

In ACR, the RGB reading of the red patch (before any adjustments) is 196, 54, 59.
In the Profile Editor, the RGB of the same file and same red patch is 55, 20, 11.  

What do the DNG Profile Editor's RGB/HSL/Lab readouts mean colorimetrically?
The RGB/HSL/Lab numeric readouts reported in PE are computed based on scene-referred ProPhoto RGB linear coordinates.

... first adjusting the grey patches (which can't be done in the Profile Editor, so I presume this would have to be done in ACR first ...

It's not necessary (at least not for building a 2D Hue/Sat.-profile).

Just run the Chart Wizard !

Peter

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