I'm looking at the Shure 840 professional monitoring headphones and was wondering if they will be the proper type of headphone for:
- location sound recording for video including dialogue and folly sound
- listening to music/creating soundtrack music
I've not used them myself, but just going by the specs on Shure's site, I don't see why not. Shure is generally a good name in audio production, although I know them more for microphones than for headphones.
The 840s are circumaural ("goes around your ears") and so will probaby not leak audio very much, so they shouldn't interfere with your location recording, and they collapse which might be convenient for transport. The cable appears to be coiled though, which is nice but more of a "sitting next to some hardware" kind of convenience. Make sure your field work won't be impeded by this.
For listening and composing music, they should be fine (they appear to be designed for studio monitoring, and the website says as much), although for really critical listening like mixing it's generally agreed that a proper set of monitor speakers in a treated room is best.