Congratulations to Bill Veik, whose bright, bold image of a hot-air balloon rose to the top of our list of entries for last month’s project on “pressure”. See the rest of our favourites in our online gallery.

This month, we would like you send in your images on the theme of “light”, so whether it’s rainbow reflections of a puddle of oil or the glint of a waterfall we want to see it – but don’t forget to let us know how you took the shot.

You can share your photos by clicking on the blue ‘Contribute’ button on this article. You can also use the GuardianWitness smartphone app or the new Guardian app and search for ‘GuardianWitness assignments’.

Our favourite will be in the November issue of Observer Tech Monthly while the best of the rest will appear in the online gallery.

Closing date is 30 October.

• GuardianWitness is the home of user-generated content on the Guardian. Contribute your video, pictures and stories, and browse news, reviews and creations submitted by others. Posts will be reviewed prior to publication on GuardianWitness, and the best pieces will feature on the Guardian site.