HVX900 variable framerates question

[Bruce Greene]

Paul,

Yes, what you’re missing is the timing of the frames. When you shoot at 60p, you shoot one frame every 1/60th of a second. To get to 30FPS you’ll be ok by just dropping every other frame and you’ll get 30 evenly spaced frames for every second. To get 50 FPS from the 60P footage you’ll have to keep most of the frames, dropping one every once in a while if you will. Thus the motion will be uneven. It will be just like when you shoot 30FPS and try to convert it to 25FPS or 24FPS. The dropped frames are obvious by their timing.

The Varicam on the other hand will shoot 50 evenly timed frames per second when set to 50FPS (or 48FPS or any other setting) Duplicate frames are slugged into the tape that are flagged for disposal later (to fill the 60P requirement of dvcproHD), but the real frames will be shot every 1/50th second not every 1/60th sec like on the 900.

I hope this makes sense as written.

-bruce

[Paul Mogg]

Thank yoiu, I see what you mean, you’re saying that if for instance you want a 5fps slomo, the Varicam only records those actual 5 frames every 1/5 sec and pads out the 60p stream that goes to tape with dupes.

But still, it seems that if you’re happy with variable framerates on the HVX900 that are wholly divisible into 60, such as 6,12,15 etc., if you have software that can create a stream from every other 6th, 12th or whatever frame within the 60p stream, the timing at which the frames were recorded will have been correct, and therefore the slomo should be correct. Assuming of course that you set your shutter speed to produce the desired motion blur for the target framerate. Anything wrong with this?

Paul

[Michael Brennan]

The main difference is the exposure time per frame, an ideal example is timelapse of a freeway at night where moving lights become more blurred wioth slow shutter speed. Most of the time you need a 1 second exposure to get the car lights formed into a continuous line, depends on their speed and how close cars are travelling!

Ramping effect has been done for years in post using 50i and 60i originated material you must have seen the subtle difference?

Slow shutter speed and memory cache would seem to be widespread (optional) features these days, so the ramp feature is probably detuned in the 900 to create a difference in the marketplace between it and Varicam?

Mike Brennan