I did an interesting commercial last week Every shot was at 48 fps. A couple of weeks before that, I did reshoots on a movie that had a push in at 3 fps. Normally, I can judge, from what the shot is, what kind of speed I need to go. An actor has a revelation, generally leave on a look and depending on what the revelation is, you'll know what speed to go. High speed (overcranked shots) especially screw with your timing. You generally have to figure out what you would normally do and go twice as fast to get the same effect at 24 fps. Go too slow, and the move will barely register. Normally this is a one shot thing, meaning it's a special shot that you'll do once and then it's back to normal. When you do it all day, for two days, things get a little surreal, because you're screwing with your natural sense of timing. After two days of doubling speed on everything, I could no longer tell what I was supposed to do and had to just rely on the director (who was great) to tell me faster or slower after playing it back at normal speed. The 3 fps shot was another set of problems. High speed shots tend to be very forgiving in terms of surges or stalls or even bumps. Undercranked, especially extreme undercranked shots require you to creep, probably the most difficult dolly shot there is, and do it very consistently. Any surge or variation in speed will jump out when the shot is played back at normal speed. As I mentioned in an earlier post, I cheat a little on undercranked shots. I lay the track on a slight slope and then let the dolly's momentum carry it at a consistent pace while I just offer resistance (you can't always do this depending on how the shot is set up, on say a tight lens on a particular object, unoperated.) It all depends on what the shot is but generally you can get away with it. Anyway, usually, when the director says, "same thing at 36 fps," or 48, or whatever you will automatically increase your speed to match ( but not always. Always ask the director first. Sometimes he (or she) will want the move to be slow motion also). As a dolly grip, you get used to thinking in percentages of speed (as in take 15 percent off) and this helps. I hope this isn't too confusing. Please add any insights you may have to the comments.
Kevin sent me to his website which has some beautiful high speed work. Check it out at http://studiobattlerattle.com. He does really high speed work (1000fps). I've never done a shot at that speed before (generally speeds like that are for effects work) and I suspect it would be motion control at that point but I'm willing to give it a shot. Check out the site. There are some really gorgeous water shots.