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?