1 person found this helpful
There's no way in Lightroom to associate a RAW with a JPG and have the edits and metadata transfer from the JPG to the RAW. (Although maybe there's a plug-in to do this, you'd have to search).
But RAWs don't use more mobile bandwidth than the corresponding JPG, unless your camera allows you to reduce the size in pixels (not megabytes) of the JPG compared to the RAW.
Looks like Aperature had a feature to import RAWs after the fact, to associate with previously imported JPGs, but Lightroom doesn't. Here's a post and some comments https://photoapps.expert/tips/2015/10/9/petitioning-adobe-add-rawjpeg-support-lightroom#.W VkQKrHF2hA
As dj points out there is a third-party plugin that allows you to do this by later associating the newly imported raws with the jpegs you already had and had edited so that part can work. However, it is not easy to just import the jpegs on your iPad. You have to manually select just the jpegs in the file import. Possible but a pain. Also note that one of the biggest annoyances of LR mobile on iOS is that you have to import twice. Once to the iPad's photo roll and second to the Lightroom mobile library. I wrote about this issue over a year ago here: Jao's photo blog: A mobile workflow with Lightroom? and it is still valid even though LR/mobile has improved by leaps and bounds since then.
The bandwidth issue is a very real one. On travel I often run into horribly bad hotel internet wifi and syncing is just not feasible in a realistic time frame. I can see why you'd want this sort of workflow. I would still recommend a very lightweight laptop (a MacBook air, Microsoft Surface or something similar) over an iPad for Lightroom on the go work for now.
Thanks for the help guys. One of the problems with using LR with a laptop while travelling is that you cannot then use Lightroom Mobile at all! This is because LRMobile only syncs with one catalogue, which is the big catalogue on your desktop computer at home, not the temporary travel catalogue you are using on the laptop. It would sure be nice if LRMobile could sync with two catalogues, or if you could move a synced collection from one catalogue to another while maintaining the URLs you've shared.
Also, if I can use LR mobile on the iPad, and if it does get around to syncing over slow Wifi, I get both an online backup of the 2048 pixel versions, and a version back on my desktop computer's (backed up) hard drive at home.
What I do is to carry my main catalog with me on a external SSD drive. This syncs to mobile wherever I load it. This works great but has the disadvantage of not having backups indeed as you mention. It's a pity that (currently) LR mobile can only sync to a single catalog. This will get solved but currently is a major limitation.