I'm not sure you can add keywords on import, but once pictures are in the catalog you can select all in the library mode for your imports and universally add keywords there all at once. I'm may be proven wrong, of course.
Thanks - unless I'm misunderstanding you that's a manual change, right? In other words I'd have to select all the photos based on their EXIF info and then add a keyword to the bulk-selected photos. This is what I have been doing but I was hoping there was a more automated way so that I wouldn't have to do it manually every time.
If there's some automated way to do it in the catalog though that I've missed please clarify as that would be great news!
It's been a while since I did any scripting in Lightroom but I think what you want should be possible (though it might not be at import, you might just need to run the script on the files after you've imported them). Try Googling "Lightroom Lua Script SDK" and there are some guides on how to get started. you should certainly be able to pick up the EXIF info on the lens and write something to a custom filed, nor so sure about the Keyword field, seem to recall it was a tricky one (but that may have been reading from it rather than writing to it....as I said been a long time and my scripts were pretty basic). There used to even be a Lua Scripting forum here...not sure if there still is. Good luck!