Anyone here use the Fors ACR Script and Gretag color card to calibrate ACR?

As an amateur photographer without a real controlled lighting setting, what would be the best way for me to shoot the color card?

I think you need to shoot the card before you shoot your pics and in the same light.

Lighting changes all the time. You probably need a setting for morning/evening, mid-day, full sun/shade. Basically all the situations you are likely to encounter.

Then select the most appropriate.

I don't think you can shoot it once, calibrate ACR and hope it will then be accurate for all instances.

Graham

I do this when I am in the studio alot. Sometimes outdoors. But in a sense I shoot the color chart on each shoot/change.

Instead of trying to correct one photo at time, the script does it the first time, and I can apply the setting for that entire set. Save alot of time.

My understanding is different. I thought that once you shoot it under controlled lighting, you will be calibrating to the way your specific camera interprets colors and not to the specific conditions.

This was my understanding also, though I've yet to try it.

Yes, but unless you shoot in those same conditions, the calibration will not match.

For example. In the warm sun, the reds might be quite warm. In winter shade, they might be quite cool. The reds are not the same colour basically.

If you calibrate for a mid red, that is all it is accurate for. The sensor will not necessarily be consistent in it's interpretation of the colour when viewed in different lighting conditions.

This is all highly speculative and I have no way of backing it up - I don't have a colour card yet.

Maybe someone can try it and see?

Graham

I just took a look at the Chromoholics web site and it says that the script "finds calibration settings that fine-tune the behavior of Adobe Camera Raw's built-in profiles for your particular camera". There is a video stream there that shows how to use the calibration script and one step sets your white balance based on the 2nd white block. The output of the script is recommended settings for ACR that you can use as your defaults.

So, it appears that once the ACR setttings are tweaked for your camera, you adjust to changing light conditions by setting the white balance as you normally would.

P.S. - If I get some time this weekend, I'll give it a go.

I'd be interested in the results.

Cheers.

Graham

ACR uses a proprietary method of color balancing. Two color profiles are built for each camera model, one based on daylight conditions, the second on tungsten lighting. The ACR sliders for adjusting temperature and tint simply interpolate (or extrapolate) white balance between these two internal profiles.

When you calibrate with the Flores script, you are, in effect, adjusting ACR's internal profiles. The profiles are matrix-based and define RGB primaries for daylight/tungsten (in the same way that some ICC profiles define primary RGB values for a color space). You shift the primaries when you move the calibration hue/saturation sliders. Every discussion I've read about using the Flores script suggests shooting a color calibration target under daylight conditions.

You could also use the ACR calibration sliders to create custom profiles for any lighting conditioning. I have a calibration for gymnasium lighting where I frequently shoot sports. It's not perfect, since lighting in a gym cycles constantly. But it definitely helps. This type of custom profile re-defines "daylight" for the ACR color engine.

Note that the ACR profiles are not the same as custom lookup table-based profiles which permit fine tweaks of the camera's color response. ACR has no provision for using such third-party profiles, a weakness in the ACR approach that is a source of constant criticism.

For more, see https://photography-on-the.net/forum/showthre​ad.php?t=111375

Woody - Thanks for the detailed explanation!