Monday, October 19, 2009

Automating camera colour calibration in Lightroom/ACR

If you want to calibrate your (or any) camera sensor and are using Lightroom (LR) or ACR here are the steps:

  1. Acquire a Macbeth (or x-rite) colorchecker chart (extremely useful to have for a range of tasks including this caliibration process - though not cheap)
  2. Shoot the colour chart RAW at each ISO setting and in the lighting environment you will do the most shooting; check the web for information on best lighting. Ideally shoot the sequence in the two lighting environment you use most (e.g. daylight and tungsten if that is your mix)
  3. Import these RAW images into lightroom – converting them to DNG on import.
  4. Download and install the x-rite colorchecker passport software from x-rite. Importantly, do install the Lightroom plugin
  5. Use the LR colorchecker plugin to create and save a camera calibration file for the image(s) taken at each ISO, ensuring you create a name specific to the ISO. If you are using images shot in two light settings, the plugin will recognise this and create a dual illuminant profile automatically.
  6. Restart Lightroom so that it recognises the new camera profiles
  7. Make sure you have set the LR preset preference to make defaults specific to both camera and ISO setting.
  8. Go to each of one of the calibration shot series. In the develop module, for each of the images in turn:

  • select the newly generated calibration profile for the same ISO as the image you are editing
  • set sharpening and noise reduction to your preference, then
  • click alt (or for Macs I think cmd) reset to make the profile, noise and sharpening settings the default for that ISO setting and camera.
From here on simply import images normally - LR will attach the correct colour profile and initial sharpening/noise reduction settings automagically...
Alternatively you can download the Adobe DNG Profile Editor (DNGPE) from the Adobe labs site. You can then use the profile creator functionality within DNGPE to create the color profile for each ISO, saving it to the appropriate location (In Windows XP it is C:\Documents and Settings\ [user] \Application Data\Adobe\CameraRaw\CameraProfiles. In Vista it is the same area under 'program data'. No idea on a Mac - sorry! Then pick up the above steps from #6
The question you should ask of course is 1) why do this and 2) what are you getting as a result that is different from downloadable profiles?
  1. You would do this if you need or want to match colours as precisely as possible all the way through your workflow from capture to output. To make this worthwhile every part of the workflow also needs careful calibration.
  2. The advantage of this approach is that it ensures the colour response is as uniform as possible across the ISO range. There is a significant and perceptable shift as ISO goes up. Downloaded profiles do not take this into account. If you follow the method outlined above you will end up with a "neutral-as-possible" colour profile at all camera settings. Downloaded profiles offer both neutral "tweaked" response curves for the various subject matter - but not adjusted to ISO as you will see if you apply them to your calibration shots!
You could use the DNGPE to create tweaked profiles as well - but from my perspective this does not seem sensible. I personally want a neutral calibrated response in images imported into LR from which I can then use LR make any adjustment I wish to change the look of an image. LR offers great power in its presets to manage and standardise this process separately and I think it much cleaner both logically and in terms of workflow to keep this separation. Chacun à son goût of course.
I am amazed and delighted by the power Adobe has provided us to do all this; the results I feel are simply outstanding and something never before possible. Automatic colour calibration for every camera body with absolutely nothing for the user to think about or do once the calibration has been done. You can just focus on the creative process, knowing colour issues have been dealt with as well as is possible in this day and age. What a great age to live in as an image maker!

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