# Keyer vs comp

**URL:** <https://forum.logik.tv/t/keyer-vs-comp/8892>\
**Category:** Flame Questions\
**Tags:** compositing\
**Created:** [August 1, 2023, 10:11am UTC](https://forum.logik.tv/t/keyer-vs-comp/8892 "2023-08-01T10:11:21Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![paul\_round](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/paul_round/32/389_2.png) [@paul\_round](https://forum.logik.tv/u/paul_round)\
**Post date:** [August 1, 2023, 10:11am UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/1 "2023-08-01T10:11:21Z")

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Can someone explain why I get these different results, they are both difference matted with the original scan, the only difference should be that I’ve added embers to a fire.  
The top image is the result of using the MK, the bottom is using the resulting matte from the MK, but with a comp node.  
What extra processing is going on in the MK node?

 ![20230731_121403_copy_1612x726](https://us1.discourse-cdn.com/flex020/uploads/thedepartmentofexternalservices/original/2X/1/1c88f613b8c64189690ca5fd60e63d6d07634e03.jpeg)  
 ![20230731_121430_copy_1612x726](https://us1.discourse-cdn.com/flex020/uploads/thedepartmentofexternalservices/original/2X/a/a9a2d0586581c05c4b42d6015403ff7107e0ad07.jpeg)

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**Author:** ![hildebrandtbernd](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/hildebrandtbernd/32/3038_2.png) [@hildebrandtbernd](https://forum.logik.tv/u/hildebrandtbernd)\
**Post date:** [August 1, 2023, 10:53am UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/2 "2023-08-01T10:53:31Z")

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Does clamping do any difference? Somehow it looks like the MK differences between the unclamped result.

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**Author:** ![paul\_round](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/paul_round/32/389_2.png) [@paul\_round](https://forum.logik.tv/u/paul_round)\
**Post date:** [August 1, 2023, 11:01am UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/3 "2023-08-01T11:01:44Z")

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No difference when clamped.

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**Author:** ![Sinan](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/sinan/32/155_2.png) [@Sinan](https://forum.logik.tv/u/Sinan)\
**Post date:** [August 1, 2023, 8:18pm UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/4 "2023-08-01T20:18:49Z")

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Care to share a screenshot of the batch schematic?

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**Author:** ![johnt](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/johnt/32/14040_2.png) [@johnt](https://forum.logik.tv/u/johnt)\
**Post date:** [August 2, 2023, 5:52am UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/5 "2023-08-02T05:52:17Z")

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If you gamma up your screen can you see any noise in the second option?

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**Author:** ![paul\_round](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/paul_round/32/389_2.png) [@paul\_round](https://forum.logik.tv/u/paul_round)\
**Post date:** [August 2, 2023, 9:44am UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/6 "2023-08-02T09:44:02Z")

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No, both images are with the screen gamma’d up a huge amount.

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**Author:** ![paul\_round](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/paul_round/32/389_2.png) [@paul\_round](https://forum.logik.tv/u/paul_round)\
**Post date:** [August 3, 2023, 2:55pm UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/7 "2023-08-03T14:55:07Z")

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Hi Sinan, I can’t really share the clips involved, but it’s a straight luma key, with a couple of gmasks.  
The only difference really is the way its comped over, comp node vs MK result node.

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**Author:** ![Igor](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/igor/32/2836_2.png) [@Igor](https://forum.logik.tv/u/Igor)\
**Post date:** [August 3, 2023, 3:14pm UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/8 "2023-08-03T15:14:05Z")

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Is ti maybe that MK divides the input in order to un-mult it and that’s pushing some rogue pixels through?

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**Author:** ![paul\_round](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/paul_round/32/389_2.png) [@paul\_round](https://forum.logik.tv/u/paul_round)\
**Post date:** [August 3, 2023, 3:18pm UTC](https://forum.logik.tv/t/keyer-vs-comp/8892/9 "2023-08-03T15:18:12Z")

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Fred? Can you shed some light on this?