There is quite a bit of documentation on an issue where converting your Lightroom 3 library to Lightroom 4 compatability loses any custom tone curves you have applied to images, so I have refrained from moving into Lightroom 4 quite yet, as tempting as the new features may be. I’m still advising adventurous users to backup their libraries first, and run LR4 on a test-drive basis, instead of assuming that the end of the beta period means its time to integrate LR4 into their daily workflow.
But today’s issue has more to do with the interaction of Lightroom 4 and Photoshop CS5. Lightroom 4 comes with Camera RAW 7.0, which is compatible with all the new functions the app has to offer. However, Photoshop 5 still includes ACR 6.6. There is an ACR 6.7 RC (release candidate, meaning not yet final) version on the Adobe Labs site; which is not the usual location for downloading software updates, its more like the photography equivalent of a chemistry set, with various interesting items, some of which will never see official release, others of which just need a bit more testing first.
But the problem is that the Process 2012 (we can assume this is shorthand for the processes added into RAW conversion options in the year 2012) is not actually supported by this 6.7RC. There have been various messages flying back and forth on the Adobe Forums about the issue, the fix, the lack of a fix in the fix, etc.
So a chicken and the egg situation ensues: an image edited in LR4/ACR7.0, opened into PSCS5/ACR6.7 will then use Process 2010 (I don’t think we need to deconstruct this one), which loses you the adjustments you’ve made with your bright, shiny new controls in Lightroom 4. At least it offers a warning that this is going to happen.
This means that perhaps we are now waiting, not just for the first bug fix update to Lightroom 4, but for the next build of ACR for Photoshop CS5 as well (I refuse to bring Photoshop CS6 into the picture). Given the complexity of the situation, I may well have made one or more technical errors in what I’ve written above, or there could perhaps be a perfectly viable workaround… though if so, its a fair distance around to find it.