• Adobe After Effects

  Car perspective

  Posted by Lou Cannizzo on April 11, 2011 at 11:42 am

  Hi dave!

  We are planning to do a 2 shot of a person driving a car. The camera is shooting the windshield so the green screen is behind the rear window.
  We went out and tested the shot and to my suprise, my horizon and perspective were off. Simply raising or lowering the background plate didnt do it. I always wanted to orbit/rotate the backplate to line up with the foreground. I felt it looked like a saturday nite live skit.

  So my questions is:
  How would you plan & film so that the 2 plates line up? Is there a mathematical approach?

  For example, If I were to shoot the car on the street, I would have actor & background already composted. Now, if I placed a green screen behind the rear window & filmed it, then moved the car away to film the back plate. I would have the exact, perfect composite because all the elements are in the exact place. So, how would I get those results without doing all that?

  Am I making any sense?

  Lou Cannizzo replied 15 years, 4 months ago 2 Members · 5 Replies
• 5 Replies

• 

  Roland R. kahlenberg

  April 11, 2011 at 2:52 pm

  Markers on the green screen should help if they’re sufficiently clean. Camera height for the second shot is crucial. Some optics distortion will also be required. And then a reflection pass. So, nope I don’t know if there’s a mathematical formula.

  HTH
  RoRK

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• 

  Lou Cannizzo

  April 11, 2011 at 5:42 pm

  Hi, ok I think you guys are onto something.
  But justto be clear, I am going to pick your brain.

  1st. Camera height:
  So let’s say the camera (5D) is set to 60″ from floor to nodal.
  When filming the background, the camera has to be 60″ from ‘Outside ground” to nodal inside the car or truck?

  2nd.
  Vertical poles:
  Are the poles for tilt angle?

  If I understand you, this is what I would do:
  Set the camera up & frame up my shot to film.
  Measure the height from floor to nodal.

  Measure the distance from Nodal to Vertical poles.
  Place markers on pole so that when I look in the viewfinder, the markers are at the top & bottom of the frame.

  Now, When filming the background, I have to re do all of the steps above?

  Althought this sounds very mathematical, why do I get the feeling that I am in for a big suprise?
• 

  Lou Cannizzo

  April 11, 2011 at 5:46 pm

  Oops, I forgot to add Focal length.
  So if the DP zooms in on the shot Is there a way to know how much he zoomed in? The camera will be the canon 5D
• 

  Lou Cannizzo

  April 12, 2011 at 1:46 pm

  DAVE And get that stinkin’ H.264 footage made by the 5D converted into a decent codec before you start cutting and doing effects.

  Ok dave, now you’re scaring me. In the past i’ve worked with Canon XHA1 & 35 mil converted to proRes . Next Week, we will be using the 5D. When I said to the DP isn’t there a problem with the 5D on Linear programs or After effects? He replied, The entire School at NYU uses it and NO ONE complained.

  So dave the old mighty & Wise,
  What am i in for when this DP hands me the Flash card and says…”Quick ! Key this footage and email it back to me by tonight! ”

  DAVE SAID” Vehicles rarely travel on silky-smooth roads in a straight line. The hit potholes, ruts, sewer grates and the like. They accelerate and decelerate.

  That was my other issue.
  When we brought the test footage back, it was VERY BUMPY. We had it on a tripod in the car.
  So I tried 2 things.

  1. I stablized the motion (which turn out to be a nightmare because I had nothing stable to track)”

  2. I applied the motion of background to the interior of the car. So now the driver is moving to the background.

  Since the background was bumpy. so was the driver and this was too hard on the eyes so I semi stablized it using PRODAD. I then tracked the stablish footage and applied that to the driver and got nice results.

  SO my question to you is:
  What ways would you go about keeping the 5D from Virbrating , jumpy up & down while filming? Any thoughts?

  And did I mention that this is my first time with the 5D? So I have no Idea what to expect when importing into AE.

  Thanks for your help,
• 

  Lou Cannizzo

  April 12, 2011 at 6:10 pm

  Well dave,….we would have done that.

  We need to close down the hwy and roads to do that for 1.

  2nd. We need 1 million dollar liability insurance for the actors in the car.

  3rd. We need Permission from the town of Albany.

  Or

  Shoot green screen an call it a day.

  So basically,…no ideas to absorb shock?

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