Hi, I've just made a video which explain how to remove the fisheye effect on an action cam (like GoPro) video with Hitfilm 3 Express
Yeah, unfortunately that doesn't actually work. I did mention it some time ago, but I guess it's not used by enough people to be worth improving, or those that do use it think it's acceptable as is.The GoPro lens isn't uniformly distorted from the centre to the edge, so if you use that Effect you end up losing quite bit of the edges of the frame because in order to get the centre portion correct, you'll overdo the edges and they flip out the other way. The only solution for that is to crop into the frame quite a bit to lose those 'frayed' edges. Also the distortion amounts vary according to whether you're shooting in Wide, Medium or Narrow. In Narrow you can keep almost all of the frame because its hardly distorted anyway, Medium you have to crop in a little more and Wide you have to crop in quite a lot. I mainly use Wide or Medium. For Medium (I just checked with some 2.7k Medium footage) a value of about -7 is as good as it gets, so nothing like the values you're using.GoPro Studio understands this and does it correctly - especially if you're using SuperWide, as extra distortion is added by software in the camera - or there is a plugin for VirtualDub that allows you to adjust the centre portion and the outer portion of the frame with two separate sliders. You get the middle section right, which 'flips out' the edges, then you dial them back in.If you want to check it out, film something that's distorted on all sides, such as a doorway, and pan across it and up and down and try to get that effect to make it look good all the time. The best test image is something like a 5 barred gate, which has not only horizontal and vertical lines, but also a diagonal or two and you need two adjustment sliders to get that to be flat all the time,
@Palacono HitFilm 4 Pro renamed this effect to Spherical Warp and update #1 introduced a different, brand new Fisheye Warp effect tailored just for GoPro footage.
@Alladdin4d Oh yes, I'd forgotten. I just overlaid a video on top of itself with one of each different Effect applied to each with 50% transparency on the top one and the Hitfilm 4 Pro version is much better with a different shaped curve. Not sure why the scaling range has been adjusted by a factor of 100. Instead of -7 it's now about -0.07 (for Medium), but the amount of change per digit is still the same. I.e. going from -7 to -6 on the old version changes about as much as going from -0.07 to -0.06 on the new one, so it's not actually finer control. Probably makes sense to someone.
@Palacono Not sure on the scaling range. I know there'a a Grow option that affects it someway and it could be logarithmic too so when you use it for un-warping the amount of change is pretty much the same but when you go up in value to warp CGI clips so they match the GoPro fisheye, then you get finer control. Just a thought
As @Aladdin4d said, it's probably to give more scaling resolution to effects being bent out of shape to match the warp.
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