I used to have a red filter that fit the kit lens of my Minolta film camera but I haven't seen those filters in years ... no idea where they are. I don't have a physical screw-on red filter for my Canon because good filters are just too expensive these days, as is everything else. I used the digital modality in PS. There are a number of options including: pre-set red filter (kind of noisy), manual adjustment of all colours to create a red filter equivalent ( a little less noisy) and finally an adjustment called 'Calibration' under RAW filter package. Final tweaks can be achieved with the levels adjustment. Also, noise-reduction helps to eliminate the background gristle that pops up when a red filter is dialed in.
I liked the image in colour too because the sky came out soft and pellucid while the Mute swans almost glowed, which made me think of ghosts. I often contemplate images in B&W so on this occasion I felt the subject and lighting could be leveraged to really make it pop, like swans flying at night yet also being mysteriously illuminated. I mostly did it for you because I imagined that you would be sympathetic with that vision. I could be wrong ... I'm very good at being wrong ... years of experience.
