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Green tint when using an alpha matte tracking to a keyed out layer
Hi,
I have, for example, 3 layers in the following order:
1.Person on a green screen. Effects: NR, Lut buddy, KeyLight. Invisible.
2.Same as [1]. Alpha matte from [1].
3.A landscape.Since I want to work in Log Gamma I have to create layer [1] where I convert the clip to 2.2 Gamma (using Lut Buddy) and then I properly key out the green screen. Doing only this gives an expected result.
When I track alpha matte in the native Log layer [2] to layer [1] and switch off the visibility of layer [1] all the semi transparencies (like shadows) become green.
I assume it happens because it takes the green screen as a background instead of layer [3].How can it be solved?
Thank you in advance,
Mark. -
6 Replies
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Thank you for your respond
The NR (noise reduction) is needed to eliminate noise from the green screen.
Lut buddy is needed to restore proper Gamma – otherwise it is just impossible to key.
The layer below won’t pass color correction – I should leave it in Log space for now. This is actually the reason why I track matte.The key is pulled perfectly but instead to be semi transparent over the background layer; it is semi transparent over the green layer. It leads to a green tint on the background and a green spill on edges.
If I turn layer [1] visible and layer [2] invisible, the result is perfect – but it is no longer a log space and I can’t go back to log in non-destructive way.
How can I force the layer or KeyLight to peak layer [3] as background for transparency transitions?
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I think because you are using the track matte, you are circumventing the spill suppression built into Keylight. You’ll need to pre-compose those layers 1 & 2 and do a spill suppression separately.
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Hi Chris,
Tried your suggestion with no luck.
Pre-composed layers 1&2. Added Red Giant’s Spill Killer on the comp – doesn’t work at all.
I’ve tried to add Keylight on the comp, but it re-keys the footage without the ability to separate only spill suppression.Please take a look on the original issue-
Here are only layers [1] and [3] (both visible):
https://img576.imageshack.us/img576/68/keyissue.jpgHere what happens when I add layer [2], alpha track it to [1] and turn off visibility in [1]:
https://img4.imageshack.us/img4/8982/keyissuespill.jpgIt just looks like it blends it with the green screen instead of layer [3].
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Hi Dave,
1. Canon 550D
2+3. Even in ISO 160 it is noisy because of native pixel noise that doesn’t get mediated (a problem caused by line skipping). In addition the ability to gather more dynamic range using the temporal space (with temporal noise filter algorithm).
4. I believe so
5. Baseline IP-only H.264 (Canon’s)
6. No transcoding
7. I usually work in Log gamma (CineStyle). At least 2-stops more DR, greater ability for color correction and grading.Could you please take a look on the original issue-
Here are only layers [1] and [3] (both visible):
https://img576.imageshack.us/img576/68/keyissue.jpgHere what happens when I add layer [2], alpha track it to [1] and turn off visibility in [1]:
https://img4.imageshack.us/img4/8982/keyissuespill.jpgIt just looks like it blends it with the green screen instead of layer [3].
Thanks
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Actually it is CS5
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Thank you Dave.
I wasn’t happy with the result after multiple spill suppressor instances.
But I made it in other way:
Since I work in 16 bit environment and the footage is 8 bit – I built a non-destructive S-curve LUT.
8->16 bit conversion gives me additional 256 values between each step, so I just need to verify that every X value has different Y value.
So I apply this LUT, then KeyLight and then the inverted LUT. I got a perfect result without any data loss.Another way that I haven’t tried (but I think would work) is to use the “CC Composite” effect.
Thank you for your time and help!
P.S. I was wrong; I actually can pull a pretty good key in Log Gamma.
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