I am using the latest version of Hitfilm Express 2017 (5.0.6718.7202) on Windows 10 and have a problem with using high fps footage. When I create a normal 1080p 25fps Project, import a 50fps Video (recognized as 50fps in Hitfilm too) and put it on the timeline, it plays back at 100% speed (so it shows every second footage-frame for one project-frame) as expected. But when I set the speed to 50%, I would normally expect it to be fluent 50% slow motion. Instead the player shows only every 2nd of the (originally) 50 frames per second (every second footage-frame for two project-frames), so I have, instead of the expected 25 frames per second (or 50 frames per 2 seconds) only 25 frames in 2 seconds.
However, if i use an 50 fps interlaced Video (correctly recognized as 25fps), add the deinterlacing effect and set it to alternate, it gets "converted" to 50 fps and works fine, so when i stretch it, it shows all frames and gives a fluent slow mo.
These effects are kept on export too, and I know my Video is true 50fps because VLC shows all the frames. -> It seems like a bug in Hitfilm.
Thanks for your help/fix/efficient workaround!