I've been working on a workflow that makes it easy to send some images to Lightroom to effectively use it as a plug in, and to make it easy to get them back again. Before I get into the meat of how, let me start by answering the obvious question as to why you would want to do this. I know this is herasy to some, but Lightroom has some nice and creative tools for working with Raw images that simply don't exist in Aperture. Just because you use Aperture doesn't mean that you should be in denial about other software that exists. Lightroom, in my opinion is not very good at managing lots of files but it does have some really nice features. Its automatic lens correction is excellent. Its grad tool is really handy and it has really nice noise reduction functions. It also has a much better vignette tool than Aperture, and it has a really nice grain effect. While these options might not mean much to you depending on your type of photography, there may be occasions when you want to use them. Personally, I like the creativity the Develop module in Lightroom offers, but I don't like the application enough to switch full time.
But wait, I hear you say, why would you buy both? While Lightroom is more expensive than Aperture it's not much more than some of the more expensive plugins, and it offers a great deal of power, so I don't think it's too outlandish. I'm sorry if this comes across as pre-emptively defensive, but I've seen some loyal Aperture supporters on popular blogs out there get highly offended at even the mention of Lightroom being in any way superior to Aperture, and I know this idea will be treasonous to them. Anyway, I'm not saying that this is for everyone, or that I'm even suggesting you should get both, however If you do have Lightroom then here's a workflow that you might find useful.
Note: This workflow and the supporting files are provided as is. I make no guarantee as to their operation so use at your own risk.
The workflow is pretty straight forward. It relies on Lightroom's auto import ability and will use a pair of automator workflows to make the process a bit easier. Once you've set everything up you'll select some images in Aperture and then click on an icon in your dock which will send your images to Lightroom (and even switch to Lightroom for you). Once you've made your adjustments in Lightroom you'll export with a custom preset which will send the files back to Aperture.
Before we start we need to set up a few things. You'll need to create two folders. I've created them on my desktop but you can put them anywhere, however if you do you will need to modify the Automator actions I'm going to give you in a second. The two folders are "To Lightroom" and "To Aperture"
Next download these two automator workflows. I'f you've changed the Location of the folders then you will need to modify the "Send to Lightroom" workflow. Open it in Automator and under the section labelled "Export Masters" change the destination to wherever you want your folder to be. Once you've done this, make sure you save it as an Application. Then copy the other workflow, "Send to Aperture" to the following folder on your computer:
/Users/yourusername/Library/Application Support/Adobe/Lightroom/Export Actions
Just replace yourusername with your user name! In other words it is the Library folder within your home folder that you want to look in.
Finally move the "Send to Lightroom" action somewhere safe, say your applications folder (or if you have a scripts or actions folder) and once there drag it to your dock and put it beside your Aperture icon (to make things easy to find)
Now to Lightroom. We need to turn on Auto Image Import and then set up an export preset. Open Lightroom. From the file menu choose Auto Import > Auto Import Settings.
Tick the check box that says enable auto import and set your watched folder to the "To Lightroom" folder you created earlier. In the move to section choose a destination as to where you want your images to go. If you already have a lightroom library set up this is probably the place to choose. I have a folder set up just for this purpose.
The rest of the settings can be set however you please. Once you've finished click ok. You can test that this is working by either dropping an image file in the to Lightroom folder or exporting a master from Aperture straight into this folder. It should import straight into Lightroom. If it's not working make sure you ticked the check box to enable auto import
Now you need to set up an export preset.
Select any Image in Lightroom and choose File > Export. It doesn't matter what file for the moment because we're only setting up a preset and not actually going to export.
In the export location set your destination to the "To Aperture" folder you created earlier. Leave the file renaming off. You want it to be the same name as the original. Set your file settings as you want. I suggest using tiff and either 16 bit or 8 bit. 16 bit is better if you plan on making further adjustments. I have it set to 8bit currently. Leave the other options all turned off except for "Post Processing". In the After Export pop up you should see the To Aperture workflow that you downloaded earlier.
Once you've done all this click the "Add" button to create a preset and call it "Send To Aperture"
That's it were all set up.
Test It Out
Select a couple of images in Aperture that you want to edit in Lightroom and click the "Send to Lightroom" action that you put in your dock. If everything is working ok this should export your files, switch you to Lightroom, which should automatically import the files you just exported.
If you're wndering why do this instead of just exporting a master straight from Aperture, it's because I've set the workflow to put the files in the right folder and to switch to Lightroom in one click. You can of course export manually to the "To Lightroom" folder which will have the same effect.
Once you are in Lightroom, develop away to your hearts content. Once you're done, choose File > Export With Preset > Send to Aperture. This will export your files to the temp folder you created earlier then pop open a dialog box asking you which project to import the images into (select the one you exported from). You'll also be presented with the option to delete images after import. I think this is a good idea is it will keep your temp folders clean and empty. Note, if you manually manage your files this won't work. You can however "relocate masters" once you've imported them if this is a problem.
Still To Do
This is still a work in progress. There are a few things that I would like to get to work better. For example I haven't figured out how to tell Aperture t import automatically into the currently selected project. You should be able to do this, but I don't have it working yet. I'd also like the script to be able to automatically stack the modified images with their lightrom modified pairs but I'm not sure that is possible.
Anyway, I hope this is of use to some people and please let me know how you get on. Also, if you have any suggestions on how to improve this please post it in the comments. Remember once again though, I'm providing the automator actions as a gesture. they work on my system, but I'm providing them as is, so make sure it's working for you before using this on anything mission critical.