I am planning on shooting a short film with my DSLR (Nikon D5300). I want the film to be in 2.39:1 (1920x800), but my camera is recording in 16:9 (1920x1080).
I wondered if there is any way to preview the final aspect ratio on the camera's LCD screen so that I better see what will be in the frame (since the cropping will be done in post-production and I don't want unhappy surprises like being to close to my actor and then half of their head gets chopped off). I thought about building some sort of box thing with the corresponding bars on top and bottom of the frame that I can put on the screen, but this would be rather bulky.
Are there any solutions to preview the aspect ratio on the camera's LCD screen?