Slow motion footage can be a very powerful tool when editing but if not done right it can look very choppy and amateur. You really need to plan ahead and know what you want to shoot that will later be in slow motion in post. The best way I recommend capturing footage for slow motion with your DSLR is to shoot your footage at 60 fps.
The idea is to shoot your footage at a faster frame rate than you will edit it so when it does slow down it will have more fps to accommodate for the slower speed. If you try to slow down 24 fps footage in a 24 fps sequence the footage is forced to replicate footage that was never there to fill the space but if you shoot at 60 fps and edit in a sequence at 24 fps then when you slow the footage down it will be smooth.
Now, like I said before. You need to plan ahead. I shoot everything at 24 fps so if I want a great looking slow motion shot then while I’m in the field I need to capture that footage at 60 fps. If I edited all my footage in a 60 fps sequence then I would have no option for this feature.
There are many ways to do this I’m sure but there are two specifically for Adobe Premiere that I use and they are both very simple. First, I import my footage as normal into Premiere CS5.5. Here I can do two things. One, I can select what footage I would like to go to the time line and then I will right click on the clip and choose speed. Here I can change the speed to whatever I want. Well, remember that I want to keep it smooth so I figure that if I’m in a 24 fps sequence and I have a 60 fps clip that I want to run at 24 fps then I figure out what percent of 60 24 is and that will give me the appropriate speed to set my footage. In this case it will be 40%.
Ok, so that may be a little confusing and that’s why I typically do this different. While the footage is still in your bin you can right click on it and choose Modify – Interpolate footage. Here you can actually set the frame rate that you want it to portray and, again, you want 23.976 (24 fps) and your clip is good to go.
One more thing you will notice is that your slow motion footage doesn’t take up the whole screen and that’s because you shot it at 720p and your other footage is at 1080p. You can’t shoot 60 fps at 1080 on a DSLR so what you can do is while the clip is in the time line you can right click on it and choose “scale to frame size”.