[Chimera-users] how to make the background of Chimera-generated images transparent

Dear Chimera developers and users: I would like to know how to make the background of Chimera-generated images transparent. I used to be able to do this with an older version of Chimera. But with Chimera 1.8, I could not figure out how to do this. There are options in the 'Color/Background' to adjust 'Opacity', which to me means that I could make the background transparent by using 'zero'. But this did not happen. Could you please advise? Thank you. Gea-Ny Tseng, PhD Dept of Physiology & Biophysics Virginia Commonwealth University