i want to video racing and wheel spin in slow motion

[falkor]

 60d w/an 8gb, a 16gb San Disk Ultra class 10, and a transcend 64gb class 10 too

i want to video wheel spin, and tires smoking, but also be able to make them go to slow motion on video, and don't know the best, cleanest way to accomplish this.


i know the transcend card has errors when i try to video in 60fps, but really, am new, and don't understand the slow motion settings (or what to change, or set).

 any help please ?


 ps. yes, i youtubed it, but no-one goes into settings, (esp in ML).
thanks in advance.
~falkor

[dmilligan]

You get nice fluid slow motion by recording at a high fps and then playing the footage back at a slower one. Typically, record at 60fps (the max of your camera) and then playback at 24fps (typical minimum playback speed before things start to look jerky, movies use this speed, TV is usually a little faster at 30fps).

You can also use AE frame blending or a plugin like twixtor to further reduce the speed and interpolate the missing frames. If done right this can look pretty convicing, and is much cheaper than a 300fps RED Epic. A good tip for using a plugin like this is to get as short a shutter speed is as possible when shooting (which means you'll need a lot of light). With expo override in ML you can go all the way to 1/8000.

If you're card is not fast enough to keep up with 60fps you can try lowering the video bitrate with ML. But class 10 should actually be above the 60D's sd card reader's 21MB/s limit, so maybe you should try another card. I have had no issues shooting 720p@60fps on my 60D with the default bitrate on a class 10 card.

[falkor]

 thanks.
 can we use extreme shutter speeds ? 
or, can you explain shutter speeds, afaik with 60fps, i would setup the shutter at 120, and thats it.

so, i need more help with the understanding of shutter speed and fps, like a graph...as the only math equation was to double the ss..

also, any videos explaining this ?

[dmilligan]

fps is the time between exposures, shutter speed is how long the shutter is open, typically they are not the same, of course the shutter speed must be < 1/fps. Rather than refering to a particular shutter speed when talking about video most people talk about shutter angle, which is basically a percentage of time the shutter is open during one frame period (1/fps). There is a common rule of thumb known as 180 degrees, this just means you should have the shutter open 50% of the total period of the frame (they talk in degrees instead of percent which I think is silly, but you get the idea). So in your example 60fps and 1/120 shutter, this would be a 180 degree shutter. This rule is pretty good most of the time, but there are a couple of good reasons to violate it. One of those reasons is if you are shooting something intended to be slow motion. When you know you are going to shoot slow motion you want as little motion blur as possible (normal a little motion blur is desireable, hence the 180 rule). But when slowing footage down, it looks bad. Also, the software plugins that can interpolate frames and slow down your footage even more, work better when there is less motion blur, so to help them out make the shutter as fast as you can.

Here's an example of 180 degree shutter. F means start of a new frame, O means the shutter is open, C means it is closed (BTW, in video the shutter is electronic not mechanical, so it's not like the entire sensor is turned on in one instant, it actuall has to go line by line, this creates the undesirable rolling shutter effect):

FOOOOCCCCFOOOOCCCCFOOOOCCCCFOOOOCCCC