Hi everyone,
I'm delighted to find this thread because I had the same question as the original poster. I tried the method of exporting original files and opening in PS CS3 as smart objects. That seemed to work fine, except that when I double-clicked on one of the smart objects to make changes in ACR, I got this error message: "could not edit original smart object because no parser or file format could open the file".
I'll be more specific: after exporting both original LR files, and then opening each of them as a smart object in PS, I then had two files open in PS (one lighter version, and one darker). Then I dragged the lightened smart object on top of the darker one holding the shift key, and closed the window for the lightened file. I suspect that this is where the problem lies, because the lightened smart object (now sitting as a new layer in the document for the darkened one) is the one that won't open again in ACR.
Is there a better method for placing the smart objects into a document that would retain the ability to open them in ACR?
Also, the other problem with this method is that all communication with LR is lost. Once I'm finished with the composite I'll have to save to disk, and then re-import to LR.
I think I'll end up preferring the other option, which is to create virtual copies (or make snapshots) in LR with the desired adjustments and then choose "edit in PS" for each of them, then drag one over using the shift key. With this method I lose the ability to go back and change the RAW adjustments on the fly, but I gain the advantage of having the final image stacked with the original in LR.
UPDATE: I figured out what the problem was. When I exported the original file from LR the second time, I chose to overwrite the first file. Duh. Of course it would be impossible to re-open the first smart object made from that file if it was overwritten. I tried again and this time I selected "use unique names", and sure enough, it worked like a charm.
I still prefer the method of creating a digital copy in LR and making RAW adjustments there, then "editing in PS" and converting to smart objects. Seems easier than saving the new file and then re-importing to LR. But it's still nice to have the other option, especially on files where I think I may want to go back and re-adjust the RAW settings once they're open.