ACR Calibration values

philmar wrote in post #4925402
Hmmm, so THAT'S why I was underwhelmed by the response to my earlier THREAD. Seems everyone bought, borrowed or stole their presets, rather than calibrating it themselves. I too have borrowed the one from the huelight.com site (when it was available). It was a good starting point but still wasn't close enough. I decided I'll just do it myself. I bought a colourchecker and will be running a script soon enough...well, once I get a chance to shoot it outside in perfect conditions....though I admit just buying the presets sound better. Sadly I keep remembering that buying presets won't work because the whole idea is to calibrate it for YOUR camera, not a mean average of other sampled cameras.
I'll post my 30D presets.

FYI - Milker of huelight.com will post his 40D presets when he makes them available. He may be looking for volunteers to donate RAW files for him to use….which would speed up the process.

I hope you'll forgive my ignorance here, but wouldn't the ambient light temperature cause fluctuations in the calibration? I mean if you're taking shots of the colour card under a tungsten light, surely that would enhance some colours and desaturate others, causing an imbalance of your spectrum. The first time you try and use those settings for shots taken outdoors, you'll run into a problem.

Or am I misunderstanding something fundamental here?

On the whole the differences should be accounted for by setting a different white balance. I suspect, however, that you've touched on a key issue with these calibration values. It would be very surprising to me if the same set of calibration values were effective in all lighting conditions. For the best results, I would think that several 'calibrations' would be needed, with each done under different lighting conditions.

Yes. I've noticed that a profile I downloaded managed t completely blow out the red channel on some of my shots. I suspect that it might have been constructed under adverse lighting conditions.

The calibration that Adobe does, to come up with the default rendering, uses a 240 patch checker, so is WAY more accurate than the 24 patch calibration that any of us can do, and varying white balances are interpolated to get the ranges in between. Also, in reality, the difference between camera chips is very minor, meaning there's not actually a NEED to calibrate cameras.

On the other hand, the reds particularly are affected by the way camera chips read infrared light and that end of the spectrum so differently from the human eye. ACR's embedded profiles are shifted in the saturated red tones to shift towards more pleasing skintones, which aren't necessarily entirely accurate. That's why you see such a difference when applying certain calibration settings, and that's the reason the calibration sliders are available - for those who do wish to tweak.

No doubt in the future we will see further work done to improve the accuracy of the in built previews.

And FWIW, I'll run the calibration script later today to see how long it'll take on this machine, and work out a reasonable price for anyone who doesn't have CS2/CS3 and would like the Fors script run on their calibration image.

Ok, for anyone who does want the Fors script run on their own MacBeth CC image, but who doesn't own CS2/CS3, I can do it for £7.50 per image. No guarantees on it giving perfect images, it's just the same as running it on your own machine. If you can find someone with time to do it for free, that's great, but the offer's there for anyone who wants to try it but doesn't own PS.

(Hope it's ok to post that here - if not, Mod's, please remove it!)

Pete wrote in post #4928464
I hope you'll forgive my ignorance here, but wouldn't the ambient light temperature cause fluctuations in the calibration?

Not 100% sure myself... I know that I was told once that to be perfectly accurate, I'd have to shoot a color checker with every different lighting setup. This was in a studio, using strobes and a Sinar digital back and software. (So way back )

I'd presume that the WB setting would compensate for the color shift however.
Then again, ISTR that I've read somewhere that ACR does something "smart" to get "better" skintones in tungsten lighting, so that might (or might not) screw things up.

Victoria Bampton wrote in post #4933711
is WAY more accurate

They do a good job at hiding that

I have begun using a Colorchecker and the PS scripts to calibrate my 1DmkIII in each lighting condition. It takes about 10 minutes on a 3.5GHz overclocked quadcore, so I imagine it takes a good coffee break on a lesser machine. But clearly the adjustments differ for each lighting condition.

Would be interesting to know by how much

Since getting my camera back after a shutter replacement, the colour calibration I had is totally wacky. the reds are super hot.


I'm running the script right now to see what I get and if I'm happy with it.

Victoria Bampton wrote in post #4933711
The calibration that Adobe does, to come up with the default rendering, uses a 240 patch checker, so is WAY more accurate than the 24 patch calibration that any of us can do, and varying white balances are interpolated to get the ranges in between. Also, in reality, the difference between camera chips is very minor, meaning there's not actually a NEED to calibrate cameras.

IF Adobe were using only your camera to calibrate ACR, that would be true. But they use only a small sample size. Bruce Fraser and Jeff Schewe in Real World Camera Raw argue that ACR should be calibrated with a gretag colour card using your camera due to differences between cameras. The Adobe bulletin forums strongly recommend it too.

Thomas Knoll who wrote it would argue that one Philmar. But hey, if you get a result you're pleased with, that's great.

Victoria Bampton wrote in post #4933711
The calibration that Adobe does, to come up with the default rendering, uses a 240 patch checker, so is WAY more accurate than the 24 patch calibration that any of us can do

ummm... seeing how badly Adobe's does, I'm not too impressed by how many patches it uses...

Victoria Bampton wrote in post #4933711
No doubt in the future we will see further work done to improve the accuracy of the in built previews.

I sincerely hope so... otherwise I can see Adobe losing ground in the RAW arena.

Which brings up (an OT) question. Are other converters (Aperture, Rawtherapee, Silkypix, DXO, CaptureOne, Rawshooter, etc) having this same problem? Because if they are, I'm haven't seen or heard much about it.

Victoria Bampton wrote in post #4936603
Thomas Knoll who wrote it would argue that one Philmar. But hey, if you get a result you're pleased with, that's great.

Then Thomas Knoll apparently hasn't seen how images look from other people's cameras. I'm sure if I had sophisticated calibration equipment calibrate ACR for JUST MY CAMERA the images would look great too!

Don't mean any offense, but too many people say they see the strong color shifts in ACR that its hard to believe its all in our heads.

davidcrebelxt wrote in post #4936627
Don't mean any offense, but too many people say they see the strong color shifts in ACR that its hard to believe its all in our heads.

I'm not arguing that point by any means David. Indeed, for studio work, I too use calibration settings to get closer to the colours I personally am looking for. Colour perception is entirely subjective. Thomas has stated that there is indeed a shift in colour, particularly in the red tones and noticeably for Canon cameras, which is not technically accurate, and is done purposely for more pleasing skintones. That doesn't mean that everyone will like it. We don't hear from all the people who actually like ACR's colours, and there must be a fair few otherwise they wouldn't still be in business. And for those who don't like the colours, there are the calibration sliders or other raw converters, and that's great - choice is a good thing. Adobe will no doubt continue to work on their raw processing algorithms, along with everything else, but one thing is for sure - they will never please everyone. Hopefully with the passing of time, though, they will please more and more people straight out of the box.

Shot in daylight, opened in raw with image settings per instructions (no presets), ran script. got all zeros.

Zeros. Interesting. Script didn't error either. Maybe Canon did a colour calibrate when back in the shop.