ACR 5.7 and LR 2.7… and LR3, CS4, CS5 and how they all fit together

There’s still considerable confusion about the recent Lightroom 2.7 and ACR 5.7 updates and their compatibility with Lightroom 3.  To complicate it further, although LR 2.7′s basic processing matches the ACR 5.7 release, on this occasion ACR 5.7 offers additional features for LR3 compatibility.

For a start, there’s a difference between a demosaic and a process version – they’re entirely different concepts.

In basic terms, the demosaic is the initial translation of the raw data into an image, which applies to all of the photos regardless of your settings. Lightroom 2.6 and ACR 5.6 and earlier use the old demosaic.  LR 2.7, LR 3, ACR 5.7 and ACR 6.0 all use the new demosaic.  It’s such an integral part of the program that you can’t switch between demosaic versions, so if you’re using 2.7/5.7 or later, you’re going to be using the new demosaic.  That means even existing photos show more detail than 2.6, but they may also show a little more noise.

Further down the line are the processing algorithms, such as noise reduction and sharpening, which have changed so significantly this time that they now come in 2 different versions – 2003 and 2010.

  • LR 2.7 just has the new demosaic and doesn’t understand process versions or the new LR3 features such as grain.  Those new LR3 settings will not be backwards compatible to LR2.
  • ACR 5.7 for CS4 has the new demosaic, and it also understands PV2010 and the new features (grain, etc) in PV2003, for full compatibility with LR3 beta 2.  It doesn’t, however, have a UI to change those settings.
  • ACR 6.0 for CS5 has the new demosaic, is fully compatible with LR3 beta 2, and it now has a UI to be able to adjust those settings using the ACR dialog if you wish to do so.  It is missing the new cameras which were added in 5.7, due to a difference in timing, but those will be added in 6.1.

If you want to test any of this for yourself, open a file into LR3 beta 2 and apply a heavy grain setting.  Save the metadata back to the file using Ctrl-S / Cmd-S and then open the file in LR 2.7 and ACR 5.7.  LR3 and ACR 5.7 will show the grain, but LR 2.7 won’t.

Clear as mud?

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May 1, 2010 | Victoria Bampton
This entry was posted in 2 - Develop, Export & Edit in PS, LR 2, LR 3, What's New in this Release. Bookmark the permalink.
  • http://www.robertgreenphotography.co.uk Robert Green

    Thanks for the great explanation Victoria, it does clear things up putting it in simple terms like that. Am I also correct in thinking that LR3 (when it’s released) will be the equivalent of ACR6.1?

    [Yes, most likely. I'm not absolutely sure what the backwards compatibility will be for CS4 when LR3 is finally released. I'd *hope* that 5.7 will continue to be compatible with the exception of the lens corrections, but I can't say for sure yet. I'll post that when it's released. - VB]

  • Gabriel Marigo

    Actually, you can switch from the new demosaic to the old one. You can select the demosaic method in the camera calibration tab.

    [No Gabriel, that's exactly the point. You can switch between process versions in the camera calibration tab, but the demosaic is entirely different, and can only be switched by changing program versions. - VB]

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  • Gabriel Marigo

    That’s just how Adobe calls it on their programs, but the “process version” is changes the demosaicing algorithm. The reason they named it “process version” is that no only the demosaicing algorithm was changed. There are changes in the sharpen, noise reduction, recovery, fill light algorithms, so, the whole package is called “process version” instead of just demosaicing method or algorithm.
    I belive Eric Chan is Adobe’s engineer responsible for that…

    hope it helps to clear the subject..

    [Gabriel, many thanks for your comments, however they're still not accurate. You're correct that the process version covers the new highlight recovery and fill light in addition to the new noise reduction and sharpening, however I can say with a certainty that the demosaic is NOT included in that process version, and you still have to switch back to 2.6/5.6 or earlier to use a different demosaic. And you are correct, Eric Chan is on the ACR team who have been working on these changes, but he will verify that the demosaic is not included in the process version switch. - VB]

  • http://www.discovery.uk.com Fit Findlay

    It’s as clear as anything is with Adobe these days! Lightroom Queen, eh? Movies next! :-)