Canon 7d Chromakey Test

Matt Gottshalk

Matt Gottshalk

Resident Preditor
Reflecmedia Bkg
Canon 7D
Nikon Primes
Primatte keyer (AE)

CyberSecurity_KeyTest_Full.jpg
 
Decent key but the lighting is not well-matched and the grading on the girl looks a bit funky.

Noah
 
I wrapped on a 7D music video in January. 80% of it was green screen. I wish I could post some of it but that would be very unprofessional of me as we are still in post. I think its coming out ok.

One thing I have learned is that with a correctly lit green screen the 7D does just fine. You could have a $300,000 camera and a badly lit green screen would ruin the shoot.
 
jambredz said:
is it generally thought that the 7d isnt good for greenscreen? if so....why?
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The 4:2:0 color space for starters, much like other known bad formats for keying (DV, HDV, XD, etc.) that aren't 4:2:2.

Compression is a factor as well.


But as mentioned before, if you don't light your scene well, you're not pulling a good key regardless of the format you're shooting on.
 
jambredz said:
and if u transcode to say neoscene avi which i hear is 4:2:2, then ur good to go?
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Not quite. You can't add chroma information that isn't there.

I haven't used neoscene, but I've heard it will help your keying a little. But interpolating 4:2:2 from 4:2:0 just isn't the same as capturing 4:2:2.
 
handsome pete said:
The 4:2:0 color space for starters, much like other known bad formats for keying (DV, HDV, XD, etc.) that aren't 4:2:2.

Compression is a factor as well.


But as mentioned before, if you don't light your scene well, you're not pulling a good key regardless of the format you're shooting on.
Click to expand...

I wonder if someone can come up with a picture style that would help with green screen shoots. Maybe something that flattens all the green, or makes a better contrast between the green and subject.
As my understanding the picture styles tell the camera how to compress the footage so you can change what information gets trashed and what is kept.
 
kevinottawa said:
I wonder if someone can come up with a picture style that would help with green screen shoots. Maybe something that flattens all the green, or makes a better contrast between the green and subject.
As my understanding the picture styles tell the camera how to compress the footage so you can change what information gets trashed and what is kept.
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I'm not sure exactly how the picture styles work, but I'm sure someone could make one that will aid in your keying. If I recall correctly, someone came up with a picture profile for the EX series that was similar.

But if anything, it will only be a minor help. The real issue is that you're still capturing footage that uses 4:2:0 subsampling. That's about half the color resolution of 4:2:2. No editing of the picture style will change that.
 
another big issue is because of the shallow depth of field. You want your subject to be very sharp around the edges to retain edge detail, and if you're focus is off, then your edges are hazy which doesn't make for a clean key. That mixed with the 4:2:0 is not the friendliest.
 
PaPa said:
another big issue is because of the shallow depth of field. You want your subject to be very sharp around the edges to retain edge detail, and if you're focus is off, then your edges are hazy which doesn't make for a clean key. That mixed with the 4:2:0 is not the friendliest.
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I would think the DOF would be a great help, get your subject far enough and your camera far enough and with the screen so out of focus it would smooth out any imperfections in the screen, no?
 
ramdop said:
here is a music video i shoot with my 7d all green screen

all the other elements also been shoot and add in after effect

we had no problem cut the green
http://www.youtube.com/watch?v=l-ab_wTEdE0
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no offence, but with that kind of heavy grading you could have pulled this of with almost any chroma subsampling camera system.
Some of the edges looked very post-blurred, which gives away the key in most situations...
All in all very professional video of course, but maybe not the best example for pulling clean keys...
 
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