View Full Version : Speed trails.

03 March 2005, 05:24 PM
I am doing the effects for a commercial that is about to be shot on Thursday and i want to hear your suggestions on how to shot and achieve the effects.

The first shot is a man running in a street with people like speedy gonzales with speed-trails coming of him but the other people are at normal speed.

The second shot, time stops and i leaf gently drifts down while everything (people, cars and so on) is stop.

Fairly basic stuff i guess, but theirs many ways to skin a cat and i wanna make sure that i choose the most efficent way to skin it.

03 March 2005, 11:30 AM
Glad you think it is fairly basic stuff! sound like lots of compositing -

shot one
Lock the camera down!

Plates I would shoot
The speedy guy on open street
Crowded street
perhaps some forground people
Composite with a lot of masks and speed the guy up.

You could use this method to do a couple of angles.

Shot two
slow down the background and forground plates leaving the guy at normal speed ( 3d leaf? )

Where you filming this? Uk?

03 March 2005, 02:02 PM
Thanks for the reply, when i say "basic", i mean "basic" as in difficult :thumbsup:. We are shooting in Reykjavik iceland.

My idea for the first shot to shot a clean plate, then the speedy guy running straight between marks on the ground and with no other mobile elements (people, cars and such) only backdrop.
Next i would shot the all the mobile elements and instruct them to avoid the imaginary corridor that the speedy guy is running through using the ground marks as reference again.

For the matte generation i am thinking of using some sort of pixel analyzer with a difference algorithm, like MoKey and i think furnace has something like that too?? I would use the clean plate and the speedy plate to extract the speedy guy based on the difference between the 2 plates.

All of this is done with the camera lockdown, but if anybody has a idea of how to do this with a moving camera that is not motion control, i would love to hear about it.

03 March 2005, 02:44 PM
the shot was delayed because of weather there's still time for suggestions.:buttrock:

03 March 2005, 11:30 PM
I'm fairly inexperienced so please don't take my word for it, but in the past I've never had much success with difference keys, so if you can maybe do so tests beforehand to see if a difference matte produces a clean enough result.

03 March 2005, 01:15 PM
a old fashion difference keyer wont do a good job, but the new pixel analyzers like for example MoKey track every pixel and u can use that information to stabelize the footage, extract the camera movement, remove scratchs and dirt and of course coupled with a different algorithm and using a clean plate and a identical plate with the forground subject can extract a matte for the forground subject. This is alot more sophisticated then an old fashion difference keyer.

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