I have a friend who has a Canon XH-A1 these are the settings he used to shoot a sporting event
Manual mode, f 3.4, 1/600 speed, 30-frames, gain L, AGC on, White balance auto pre, signal HD, Instant auto focus mode, Image StabL on.
He says he recently shot a track meet and when he played it back it was trailing or choppy when the runners were going around the back side of the track. He says he had it in manual mode 30.
Just guessing, but, even though the manual says set fast speeds for sport, I would not, if you set at 1/50 sec you will get normal motion blur but, it should be smooth. Even the HV20 would do better than the XH-A1 it seems , it may have more to do with the computer and Premiere Pro than the camera. I bet the look on the LCD is Ok?
The problem was his shutter speed. The 1/600th speed is way WAY fast. That's great for stills of fast motion, but when used for video it eliminates all of the motion blur in the individual frames which our brains use to interpret as smooth motion.
Since he was shooting 30fps, a "normal" shutter speed would be 1/60th. As you get faster and faster than that, the crisper each frame will be and the more stuttery or stroby the motion will look. Obviously, his 1/600th shutter speed is ten times what a "normal" 1/60th shutter would be (or rather, it's one tenth, whichever way you want to look at it).
The donominator of a "normal" shutter speed is generally half the frame rate. That is, for 24p footage, it would be 1/48th. For 30p footage, it would be 1/60th. For 60i footage it would also be 1/60th (because it's still 30fps, just 60 fields per second).
There are a few reasons to crank the shutter speed up higher than normal. One would be if you like the "Gladiator" or "Saving Private Ryan" narrow-shutter look as a special effect. The other would be if you intend to slow-mo the film later (although you wouldn't crank it up nearly as high as your friend did). Otherwise, unless it's the look you are going for, the results will be stuttery indeed.
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