March 28, 2007
Camera Calibration panel tips
The Camera Calibration panel in Lightroom can be used (with a little help from Photoshop) to calibrate your digital captures to get the most accurate color. But that’s not all. If you play around with the sliders you will find that you can also use the Camera Calibration panel to do the very opposite of what it is meant for and create some unusual coloring effects.
The camera raw conversions in Lightroom are the result of many years painstaking work, in which Thomas Knoll (who with his brother John created the original Photoshop program) evaluated the color response of lots of different cameras. Basically, for each camera raw format that is supported, Thomas made two profiles which measure the camera sensor’s color response under controlled daylight and tungsten lighting conditions. Using this data, it has been possible to extrapolate what the color response will be for all white balance lighting conditions that fall between these two setups and beyond.
Now, there are around 150 different cameras supported by Adobe Camera Raw and Lightroom, and in some instances several camera samples were tested to obtain a representative average set of measurements. And other times only one camera model was actually used. But in all cases it is clear that the measurements made by Thomas can only ever be as good as the camera or cameras from which the measurements were made (and how representative these were of other cameras of the same make). Because you know, the sensors in some cameras can vary a lot in color response from camera to camera. This variance means that although a raw file from the camera you are shooting with may be supported by Lightroom, there is no absolute guarantee it will be exactly similar in color response to the raw files from the cameras Thomas evaluated. This is where the Camera Calibration panel comes in, because the Camera Calibration panel sliders can be used to make fine-tuned adjustments to the camera’s color response.
Figure 1. The Calibration panel controls.
Creating a custom calibration via Photoshop
If you have Photoshop CS or later, there is a way to automatically create a custom calibration for your camera that involves the use of Thomas Fors ACR Calibrator script. This script will work for Mac or PC and can be downloaded from: http://fors.net/chromoholics/. Install the script in the Photoshop application/Presets/Scripts folder, then restart Photoshop and follow the instructions on the page opposite. The script will open a new ACR Calibrator Status Window (see Figure 4) and run through a series of steps, in which the raw image containing the color checker chart will be opened many times using different settings and measure the results. This process can take a very long time to complete, which is why it is important to keep the bit depth at 8-bits per channel and the image size small. It will also help if you hide all the palettes first before you run the script. Note that apart from setting the bit-depth to 8-bit and the pixel dimensions to the smallest output size, there are no other settings you need concern yourself with. It does not matter if the auto settings are on in Photoshop or not and it does not matter which RGB output color space is selected.
Figure 2. To use the ACR Calibrator script, you will need to photograph a Gretag Macbeth ColorChecker chart and open the raw file via the Adobe Camera Raw dialog in Photoshop. Use the white balance tool to measure the circled patch (next to the white patch). Next, crop the image tightly around the ColorChecker chart, set the crop size to the smallest resolution possible and set the bit depth to 8-bits per channel. Now click Open to open the image in Photoshop.
Figure 3. With the image open in Photoshop, select the pen tool with the Paths mode option selected in the Tool Options bar. Click with the pen tool on the brown patch followed by the white patch, the black patch and lastly the blue-green patch. Now go to the File ➯ Scripts menu and select the ACR Calibrator script. The script will automatically open the raw file many times over and gradually build a Calibrator status report in a new Photoshop document.
Figure 4. Here is the ACR Calibrator Status Window after the script has run its full course. I have highlighted the calibration settings in yellow. You need to note these figures down, enter these in the Calibration panel in Lightroom and save these as a custom calibration setting for your camera. You may also want to make a note of the Color temperature white balance and Tint settings and save these too as part of your custom calibration setting. That’s it, you are all done and the calibration setting you have created should be good for a variety of color temperature settings.
Camera Calibration panel color effects
But as well as using the Camera Calibration panel to get accurate color, you can also use the Camera Calibration panel to produce different color effects.
Figure 5. This shows a standard version of an image with zeroed Camera Calibration panel settings.
Figure 6. This is a vivid color setting that was created using the following Camera Calibration settings:
Shadows: 0
Red Primary Hue: 0
Red Primary Saturation: +85
Green Primary Hue: +85
Green Primary Saturation: +85
Blue Primary Hue: 0
Blue Primary Saturation: +50
Figure 7. To create this magenta sky effect, I used the following Camera Calibration settings:
Shadows: 0
Red Primary Hue: -40
Red Primary Saturation: -40
Green Primary Hue: +30
Green Primary Saturation: +30
Blue Primary Hue: +80
Blue Primary Saturation: -100
But in addition, I adjusted theHSL panel luminance, lightening the yellows and greens to +35 and darkening blue to -35 and darkening purple to -14.
Figure 8. To create this color infrared effect, I used the Camera Calibration settings shown here.
Shadows: 0
Red Primary Hue: +70
Red Primary Saturation: -30
Green Primary Hue: -45
Green Primary Saturation: +20
Blue Primary Hue: -100
Blue Primary Saturation: -40
In addition to this I set the Shadows in the Split toning panel to Hue 180 and Saturation 25. Bear in mind that with all the settings figures shown here, these are just guidelines. You will find that individual images may suit slightly different variations.
Figure 9. You can of course save the Camera calibration settings for settings such as the infrared color effect and apply them to other images. But it doesn’t always work so great on portraits.
This article is an excerpt from The Adobe Photoshop Lightroom Book by Martin Evening, which is shipping now. In special arrangement with Martin and his publisher, PhotoshopNews has a free PDF download of Chapter 1. (click HERE to download-4.6MB PDF)
The Adobe Photoshop Lightroom Book describes Lightroom’s features in detail and with photographers in mind. Photographers who routinely work with raw (and even jpg & tiff) images will find Lightroom–and The Adobe Photoshop Lightroom Book–an indispensable tool in their digital darkroom.
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The Adobe Photoshop Lightroom Book
by Martin Evening
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I simply don’t understand who will want accurate color? None of the films were designed to do that, nor todays digital cameras.
It seems, Maxos, not to start an argument, that you have not been on the Adobe Lightroom Fora much, U2U and the earlier Open Betas, or you would know that there are plenty of people that insist the RAW image as developed by LR ‘must’ match the JPEG as they saw it in the Camera, that being their idea of ‘accurate’ color!
Makes you wonder whatever happened to ‘art’.
:)
Don
Because digital is different to film. With the right equipment you have the potential to capture very accurate colour (with the help of camera calibration), or you can bypass such accuracy and process an image any way you like and with far more flexibility than you could with film. Basically you can have it both ways: accurate or arty. The choice is yours.
The term ‘accurate color’ is a bit of a misnomer. We really want pleasing color. Accurate color, at least by my definition is scene referred measured (spectral) color you’d find if you actually measured the color at the source. Or what is known as colorimetrically correct color. This paper might help:
http://www.color.org/ICC_white_paper_20_Digital_photography_color_management_basics.pdf
What we want is pleasing color. Color that represents the scene as we remember it or want to express it on some device like a print or display. Scene referred color is often pretty ugly. The article above found on the ICC site explains this pretty well.
All the stuff you see in LR (or ACR) is output referred.
Andrew,
Your comment to means simply that we are artists and are looking to recreate our vision of the scene. (At least it does to me!)
Oops, left put a me there! “to me means”.
>Your comment to me means simply that we are artists and are looking to recreate our vision of the scene. (At least it does to me!)
Well yes since if you colorimetrically attempt to recreate the scene (assuming you could fit the dynamic range and gamut of the scene onto the dynamic range and gamut of the display or print), it would look pretty butt ugly.
The times where producing a colorimetrically correct rendition are useful is copy work.
>Your comment to me means simply that we are artists
>and are looking to recreate our vision of the
>scene. (At least it does to me!)
I have noticed that my own eyes are miscalibrated: my right sees light warmer than my left. So if color cannot be “accurate” between one’s own eyes, what hope is there of accuracy between different media or rendering methods.
Pleasing color is a good term. I’ve also heard memory color — the color you remember (i.e. the memory of how your brain interpreted the color it sensed).
Daniel and Andrew, you are both very right. Now could someone tell me why ACR/lightroom are not memory color calibrated? I mean, take your nikon/canon colors our of the camera, and then take the colors ACR is producing, which do you like better?
If you think you can reproduce what nikon and canon are doing with lightroom, you are very wrong. ACR color system is a simple 3by3 matrix where nikon/canon color system is a big LUT, which is much more flaxable.
There are way more issues here than ‘miscalibrated’ eyes . Look at any white piece of paper and try NOT have your visual system adapt to the white in view (that’s not possible). Or look at this fun optical illusion:
http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html
Maxos, you have to first recognize that raw data has no color, that’s the job of the raw converter. And as you say, take both the Nikon and Canon with the same lens type and shoot the same scene in raw and JPEG and you will not get the same results anymore than shooting two film brands of the same scene. Again, both are producing output referred color based on how the manufacturer feels you’d like the color. Lastly, ACR is only providing a default rendering based on two profiles Thomas Knoll has built for one sample camera shooting a single target under two standard illuminants. The calibrate tab Martin discusses is there to allow you to, for lack of a better term, edit these profiles to produce a color rendering you prefer and then set as a new default.
As per LUT versus Matrix profiles, you may have a valid point. I don’t know enough about the underpinnings here but Karl Lang (a true color scientist) has on occasions told me that using LUT based processing (which I think he said IS done in Aperture and other products) would be very helpful.
I will surely make use of this stuff if I ever find the LR rendering to be out of whack, but for both my D200 and my D50 it’s just fine.
Has anyone seen Nikons or Cannons that have a noticeable color cast or other issue?
Jason
PS
It seems Mr. Schewe has a certain propensity for charging the lens…
HI, ACR cal. does not work with CS 3 .
Actually that is an important point that I neglected to point out. One can use Photoshop CS2 with ACR 3.4 in the meantime to process a shot of a Gretag Macbeth ColorChecker chart. After Photoshop CS3 officially goes on sale I anticipate that Tom Fors will have the later update out. In the meantime, stick to using CS2. I built a camera calibration only yesterday using CS2.
Tom Fors responded saying:
I do have a version available that supports CS3. At the moment it issues a warning about not being fully tested yet but allows the user to proceed anyway.
I’ve been giving it out to anyone who emails me about the availability: tom@fors.net
http://code.google.com/p/acrcal/
There’s also additional documentation available from the “Wiki” tab. I hope to release this soon as version 1.0.
>Has anyone seen Nikons or Cannons that have a >noticeable color cast or other issue?
Not specifically but many Nikon users find themselves in a quandary. The out of the box Lightroom conversion is generally perceived not to be as pleasing (Colour) as Capture NX, yet the ‘clunky’ NX workflow is horribly inefficient when working with anything more than about 5-10 images.
I’m optimistic ME’s tip may go some way to addressing that.
P.S. ME, Good book. I enjoyed the ‘rough cut’ approach and am looking forward to the printed version landing on the doormat.
Thanks Martin and Tom .I’ll try to be patient . Cheers.
Just tried Tom Fors’s new ACR Cal. It works fine with CS 3 .
When it comes to Camera Calibration, does the light source dictate how you calibrate. Do you need a Custom Calibration for each lighting source for example, Daylight, Tungsten, Strobe (Studio lights) and what about mixed sources?
I’m an Architectural Photographer and I shoot in many different light sources, sometimes mixed sources, sometimes I gel my lights with CTO gels to warm things up or to match the ambient light source.
How will Camera Calibration fair with what I do?
I tried Color Eyes a couple years ago but I was not satisfied with the results and did not think it was worth the effort at the time.
Thanks
Mark
According to Thomas Fors and Lee Varis , you need a different calibration for daylight, studio and tungsten lighting .
“Basically, for each camera raw format that is supported, Thomas made two profiles which measure the camera sensor’s color response under controlled daylight and tungsten lighting conditions. Using this data, it has been possible to extrapolate what the color response will be for all white balance lighting conditions that fall between these two setups and beyond.”
How does one get calibrated for different white balances? Does the Color Checker need to be shot under each type of light/WB, or just Daylight & Tungsten?
Thomas’s profile calculation cleverly calculates the appropriate colour interpretation across a wide range of white balance shooting conditions. The camera calibration enables you to finesse the colour control with greater precision. From my expereince, the camera calibration can be most important in the studio where I am using the same strobe flash units and therefore a calbration for that one source of lighting will prove useable for almost everything I shoot in the studio. Some people have claimed that the camera calibration for a strobe light source will be reliable enough to use for other lighting conditions as well. And I would say that a camera calibration applied in this way is bound to get you more precise colour than to not use it. But on the other hand, there can be variables in certain light sources that could easily throw the calculation. For example, in my CS2 Photoshop book I describe how to camera calibrate for flourescent tube lighting. I would say that for this type of lighting situation it would be a very good idea to custom calibrate.
As I await my new Mac Pro I eagerly hope that the calibration process will be amade a lot quicker!
Martin
Hi Martin:
I just ran the script on my MAC Pro, in CS3 and it took 18:12. After 47 minutes, it’s still running on my PC! :-)
David
I am relatively new to digital capture and am trying to ease my workflow. Thomas Fors’ script enabled me to generate several Develop camera calibration settings for different lighting conditions. They are an improvement over the ’straight’ image, but the greens seem too strong and some yellows are overly acidic.
As a result of this, I tried the Rags Gardner scripts on the same DNG files and obtained very different settings which puzzled me since they operate in same manner. One setting varied by over 30 units! The results seem more in line with what I am looking for, but am not entirely happy just yet. I haven’t worked out how to post attachments to illustrate how much the settings vary.
Is there a more accurate way of generating camera profiles? Surely the big players in Colour Management are losing out since their calibrators are not being used to make ICC profiles as more photographers turn to Lightroom.
It seems right that I am having to make several settings as I am using a Leica M8 with the Leica IR cut filters and expect it to be susceptible to changes in the nature of the lighting.
Many thanks
Baxter
Baxter,
You may want to consider tweaking the results you are getting to find what works for you best. I would not say that the script created setting is the one that is absolutely correct in every case. For example, skin tones can look too red when using a calibration setting and I will sometimes tweak the exact settings.
Bear in mind that under the hood, ACR is using a profile calibration method to work out the correct calibration for each camera. It has been done by measuring profile readings under two different luminance conditions and then extrapolates from this data the correct calibration for different ACR white balance settings. The data used in ACR has been collated sometimes from a mixed sample of cameras. In some cases just one camera model has been used. The default settings should therefore provide a reasonably good calibration for your camera as well,but the default calibration can only be as good as the difference between the charcteristics of your camera compared to the one that was used to create the default calibration. Some camera models may vary a lot in colour consistency between one camera and another. This is where the camera calibration process comes in. It is designed to provide the facility to fine-tune the camera profile calibration used in ACR.
Martin
I just found this thread so I’m coming in a bit late and don’t know if it’s still considered to be active.
I found the piece to be so informative that I decided to calibrate my cameras on CS3. I emailed Tom Fors about the CS3 patch/version and haven’t heard back. Am I being impatient or is this whole thread now considered to be finished up? Thanks.
Do you have any alternate calibration suggestions now that the script is wildly out of date?
Thanks again!
-Zach
The last Tom Fors update was in 2008 before CS4 was launched. I gather that there is another script out there that can be used with CS4, but I don’t have the link to hand right now. Maybe someone else can provide a quick answer. I hear it also runs quicker.