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sky replacement for a dolly shot?
Saw the sky replacement at video copilot and was very impressed. I was wondering if there was any way to do something like that, but for a clip that was shot from the back of a pickup. The sky to replace is blown out and comes in and out of the shot over a tree line.
So, the example at video co pilot seems to be 2D sky replacement and what I’m trying to do is more 3D or z-space replacement. Is something like this possible in AE or would it require something more along the lines of Imagineer’s Mokey or something like that?
Thanks ahead of time for any help! -
10 Replies
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Perfectly possible with AE. You just need a 3D tracker to do it. I can wholeheartedly recommend The Pixel Farm here. If you’re only working with SD footage then PFHoe will sort you out very cheaply (from
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And thinking about it, you might not even need a 3D tracker, just the regular 2D AE tracker. If you’ve got an object in the far distance that you can track then just use After Effects.
The secret here is to find an object in the furthest plane of your image. Otherwise the parallax motion will make it look wrong.
Or you can use a 3D tracker and let it build a virtual camera. The 2D option’s quicker!
Curious Turtle Professional Video
Training | Editing |Support -
Thank you very much for those quick responses! Until I get to play with it, I guess I won’t really know if a 2D tracker will do the job or not. But it’s worth a try!
Checked out the Pixel Farm. You weren’t kidding about the price difference! Unfortunately, the footage is DVC Pro HD from an HVX200, so we’d need the expensive version. So, I’m thinking if it doesn’t work, then I might try out Synth Eyes.
Thanks again for the help and btw, cool site you have. Wish you had more Red training on DVD though as you’re a good ways away from here! -
No probs.
[mus man] “Wish you had more Red training on DVD though as you’re a good ways away from here!”
Following hot on the heels of the our DVD Studio Pro Scripting course, we’re currently looking at which courses will translate well to DVD. The hot favourite is for a full restoration and creative color correction course. But thanks for the vote for Boris Red. It’s definitely noted!
Have fun with the tracking, and let me know if it works.
Ben
Curious Turtle Professional Video
Training | Editing |Support -
Hi,
Just to add to the above, if you end up using a single tracker on a distant object, you can add to the realism by including an expression to push the sky movement a little further in the direction of motion than the tracker sets. Maybe only a few pixels, but it can be enough to give that subtle extra realism that makes the replacement un-noticeable.
Lars
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Lars makes a good point.
Though personally I would probably push the movement a little less. All dependent on how far back your tracked item plane is, of course, and if your replacement sky has got any big obvious clouds on a near plane. The trick is to match the tracked planes. That will help keep your composite “real”.
Curious Turtle Professional Video
Training | Editing |Support -
“…a full restoration and creative color correction course.” That would be really cool as well. I just mentione Red as it was the first compositor I ever learned how to use with away proficiency. There’s a shorter training DVD, but I like the 7 disk spend a week on it version to really get to know all the in and outs.
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Thank you both for the help and suggestions. I’m a little confused though when y’all talk about adding an “expression” and how best to match the planes. Are y’all talking about possibly adding a very slight movement of the new sky in the z plane?
Sorry I’m new to this kind of thing. -
If you work with the 2D tracker then you don’t have to worry about the Z-axis in After Effects.
When I talk about planes here, what I mean the distance plane from the camera. If we look at the moving image itself, any object at the same relative distance will move in the same proportion. So, for example, we have a road with a person standing very close to the camera, a road sign in the middle distance, and a building in the far distance. If the camera were to move slightly, either left or right, or up and down, then the person close up would appear to move more than the sign in the middle distance. The building in the far distance would appear to move very slightly. Thank you parallax.
When doing matchmoving like this, it’s important that you track an object in the same relative plane, or when you put it in the composite, the object is going to behave very differently than you want. In the example above, if you wanted to put in another sign in the middle distance, then you would track the object in the middle distance. If you applied the movement of the person in the foreground then the movement will look off.
It’s the same with the sky. The sky will have very little apparent movement relative to objects in the foreground or middle distance. So this is why you want to track an object in the farthest plane you can.
If you apply this tracker motion to a Null object, you can link this to your sky layer with a simple expression that can subtly change the values in the track, so that the sky appears to be in a different distance plane than the object you track. So, say you could only track the sign in the middle distance, you don’t want the sky to follow that movement. Apply the tracker information to a Null and then use this expression on the Position of your replacement sky layer:
multiplier=0.98;
mul(thisComp.layer(“Null 1”).position, multiplier)You can change the value “multiplier” to whatever you need. If you bring it down, the the sky will move less than the object you tracked (making it appear to be in a further distant plane). If you bring it up the sky layer will move more, so it will appear to be in a closer plane. The trick is to keep it subtle. This is a very unsubtle expression, so using numbers too far from 1 won’t give you the effect you need, and the sky will look bizarre.
Wow, that’s a bit longer than I’d planned. I hope this makes sense. :o)
Ben
Curious Turtle Professional Video
Training | Editing |Support -
WOW!! I just wanted to say thank you very much for taking the time to write that all out. I think I have a much better understanding of what you’re talking about now. Seems logical.
But, I haven’t even had a chance to get in there and get my hands dirty (won’t have the footage for another few days), so I hope you don’t if I check back for a little clarification or help along the way!
Thanks again, I really appreciate you’re taking the time.
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