Sharing a Lightroom catalog between two computers
Adobe allows two Lightroom installations with a single key with a limitation that the software isn't used simultaneously on both computers. So here's a little tip for you Lightroom users like me who mostly use desktop computer but a laptop when on the go.
First of all copy or move your Lightroom archive to an external drive. Lightroom doesn't use a whole lot of bandwith when editing photos so pretty much the only thing affected is the import speed from hard drive since memory cards rarely exceed the transfer speed of even USB 2.0. Access times are slightly more critical and since USB interface increases the latency of the system I would recommend using a SSD-drive even if you don't really gain from increased transfer speeds. There's also an additional benefit of using a SSD-drive. SSD's rarely fail in a manner that causes a loss of data. The most common type of failure on a SSD is that it becomes unwriteable. USB 3.0, eSATA or Thunderbolt pretty much remove all the speed impact of using an external drive causes so if you have that option use it.
If your Lightroom catalog is large its probably beneficial to split it into an archival catalog (which you can store on the computer with more free storage space) and an active one. The speed gain of decreasing your catalog size is far more significant than the impact of using a USB-drive for your photos. This can be done easily with Lightroom's "Export as Catalog" feature. You can access your older photos simply by opening the other catalog file in Lighroom. If you're using a SSD-drive decreasing your archive size is beneficial because you can make do with a smaller SSD and save money.
Next step is to move the catalog file (the file with .lrcat extension) to a cloud storage service that allows automatic synchronizing to your local drive. I personally had some issues with Google Drive so I opted for Dropbox which works like a charm. It's better to not keep the catalog file on the external drive because it gets a lot of read and write operations and the USB bandwidth and latency really has a big impact on performance. Using a cloud storage service is smart because otherwise you'd have to copy and paste the .lrcat file back and forth manually and that's just a bit more of an hassle than I'm willing to accept.
The folder location is stored in the .lrcat file and there's a good chance that after the "Export as Catalog" it's location is marked as relative to the .lrcat file thus rendering the archive unaccessible from Lighroom. Right click on the folder in the Library view's folder list and select Find missing folder (or something like that) and select the folder you created on your external drive. Now the folder location is absolute and you should be able to access all your full resolution photos. If you configured your PCs correctly you shouldn't need to do anything else. On Mac this is a bit easier because the path is based on volume label not drive letter and that is specified on the external drive and not by operating system.
Export settings are unique to the computer you're using so you need to set them up separately. This includes watermarks. As for import settings I'm actually not sure. I'm pretty sure they are stored in the .lrcat file. I've been using both Mac and PC and these import destination needs to be set up each time you move from system to another.
One more thing. If you have a Catalog of reasonable size something like 2GB of storage Dropbox gives you should be plenty for your Catalog but you need to watch for the size of your previews folder. In this case Lightroom stores full resolution previews of your photos to your cloud storage so it can quite easily grow rather large. To negate this effect you should setup Lighroom to discard 1:1 previews for example after one week. This can be done by "Edit -> Catalog Settings... -> File Handling".
I've found this very handy since I have access to most of my photos where ever I may be, as long as I have my photo drive and a laptop with me and as an added bonus I don't end up clogging up my Macbook Air's drive with loads of photos.
If you don't have a Dropbox account and you wish to get one, you can get one with 500MB bonus on top of the 2GB default by clicking
HERE.
Hope you guys find this useful.