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-   -   Streaky edge artifact in 25p (https://www.dvinfo.net/forum/canon-xl-gl-series-dv-camcorders/100415-streaky-edge-artifact-25p.html)

Jason Wong August 3rd, 2007 09:51 AM

Streaky edge artifact in 25p
Hello everyone.

I'm using 25p,16:9 mode to do some green screen test. As far as I know, a 25p footage should provide better edge compared to a deinterlaced 50i footage.

The problem is, I'm getting this streaky edge artifact for my 25p footage.

If you'd please check the sample image that I provide, the one that I shot in 25p mode surely get a better edge definition on the area that I marked with blue circle. The problem is the streaks on the area inside the red circle.

Sample image (25p, scaled up 400%)

For comparison, the following is a deinterlaced frame from a 50i footage (using standard After Effect deinterlace method, no plugins)

Sample image (50i, scaled up 400%)

As seen from the 50i image, the edges indeed are more blurry than 50i, but without the streaking artifact.

For information, both frames were taken from footages when the subject was not moving and the camera locked-off.

I was using the Wedding preset for the 50i, and my test preset for the 25p.

(my test preset for green screen work. It's a test and it's not yet working for me. Use it at your own risk ;) )
Gamma = 1
Knee = 2
Black = 0
NR = 2
VDetail = 0
Color Matrix = 1
Color Gain = -1
Color Phase = 1
Red = 1
Green = 0
Blue = 0
SetupLevel = 4
Sharpness = -2
Coring = 5
MasterPed = 2

It surely not a problem when being seen at 100% size, but because it streaks at 400%, obviously the keying plugin (Keylight for After Effect) saw it and it became a problem (nasty edge).
I'm able to get a good key from the 50i footage, but I had to use much more matte blur&matte contract for the 25p one.

So, is this streaky edges normal, or did I do something wrong during the shooting? (wrong lighting setup, wrong camera setting, etc).


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