There’s some confusion over a dialog box which has reared its head again in Lightroom 2.2. It appears when you try to edit a raw file in CS3 rather than CS4, and warns that you need ACR 5.2 for complete compatibility.
Are Adobe saying that you have to upgrade to CS4 in order to use Lightroom? No! So what are they saying?
Render using Lightroom will create a Tiff or PSD file and open that file into Photoshop.
Open Anyway tries to pass the raw data to Photoshop, and ACR opens the file directly into Photoshop without an interim Tiff or PSD file.
CS3, ACR 4.6, and a camera that is supported in ACR 4.6 – you can press either. At this point in time, the rendering appears to be the same.
CS4, ACR 5.2, and a camera that is supported in ACR 5.2 – you can press either. They are fully compatible.
CS3, ACR 4.6, and a camera that is NEW since 4.6 – you have to press Render using Lightroom as ACR wouldn’t know what to do with the data.
Once you’ve made your decision, you can check the ‘Don’t Show Again’ checkbox to bypass the dialog in future.
With future versions, the gap between Lightroom’s processing and older ACR versions will widen, and Open Anyway may not be able to process new Develop adjustments that you’ve made in Lightroom, however pressing Render using Lightroom will always create a Tiff or PSD version WITH all of your Develop adjustments rendered correctly, so even then, Adobe aren’t holding you over a barrel.