Why shouldn't you use Keylight on Adjustment layer?

[reindeer4]

Hi -

I'm working with 6 x four minute mov files of a performer against a greenscreen for a music video (different takes for the same song; same lighting conditions)

I synced up the clips in Red Giant Plural Eyes, then brought them into Premiere Pro CC 2018, where I deleted 5 of the 6 copies of the audio track.

I then replaced the Premiere Sequence with an After Effects clip, so I have the 6 mov files on top of each other.

If I use Keylight (plus Advanced Spill Suppressor and Key Cleaner) on an adjustment layer at the top of the stack, everything keys out properly on each layer, but even though i see the white and grey checkerboard pattern for transparency, I'm not actually seeing through any of the layers to the ones beneath (otherwise I'd see bits and pieces of the performer since not in the same poses for each take - and I verified this bby placing a red solid behind different layers, and I only see through masked out areas, not keyed areas.

If I apply the same combo of Keylight, Adv Spill Supressor, and Key Cleaner to individual layers, the keying works as expected, generating true transparency.

My thought was that since the lighting and backgrounds are the same, it would be better to use a single Adjustment layer rather than 6 separate applications  of the keying effects - though I did see recommendations against putting keying on an adjustment layer on another thread.

Would like to know why I get the transparency checkerboard but not true transparency when effects on Adjustment layer.

Thanks for clarifying.

[Mylenium]

Well, apprently Keylight manipulates the transparency/ Alpha channel and that is simply different for each individual layer vs. the accumulated buffer of all layers. You simply have a misunderstanding how adjustment layers work. They are not applied individually to each layer, they are applied to the whole group as one.

Mylenium

[Dave_LaRonde]

reindeer4  wrote

...since the lighting and backgrounds are the same, it would be better to use a single Adjustment layer rather than 6 separate applications  of the keying effects - though I did see recommendations against putting keying on an adjustment layer on another thread.

Would like to know why I get the transparency checkerboard but not true transparency when effects on Adjustment layer.

Thanks for clarifying.

Those layers are NOT the same if the camera was set to Auto Iris!  That's why you're getting the results you see.

They are, however very similar.  So I would use keylight & the other effects on just one layer and get it right.  Then copy-paste the effects onto the other layers and then tweak accordingly.  Your results will be better.

Generally, the only time to use an adjustment layer is when you HAVE to.

[Rick Gerard · Accepted solution]

To put it simply an adjustment layer makes every layer below it a single layer. Sometimes this is useful but it is not if you are trying to modify the pixels in only one of the layers. Keyight is used to create transparency in a layer by generating an alpha channel based on colors. You can only effectively do that on one layer at a time.

[reindeer4]

Got it - thanks for the replies.

Was surprised by Dave's suggestion that you should only use Adjustment Layers if you have to.  Is that a general consensus?  I was operating under the assumption that Adjustment layers would make things more efficient since it avoided adding the same effect to multiple layers.

[Roei Tzoref]

Is that a general consensus? 

I am not sure what that statement means. there's nothing wrong with using adjustment layers for any purpose that helps your workflow. once applied with an effect, it's a way to affect the composite of all the layers below and that's sums up it's purpose. you should not avoid using it or avoid not using it.

[Rick Gerard]

If you have a bunch of layers and you want to apply the same effect to those layers then that may be an efficient way to go. Let's say you have 20 layers in your comp and you want to apply the same effect to layer 5 through 9. You cannot add an adjustment layer above 5 because every layer below the adjustment layer will have that effect. The efficient way to apply the same effect to layer 5-9 is to pre-compose and then apply the effect to the pre-comp.

On the other hand, if you want to apply the same effect to layer 1-4 and 9-12 you might not be able to pre-compose all of the layers because 9 through 12 will now be above layer 5 and that could foul things up, but if 1-4 and 9-12 are 3D layers arranged so they don't overlap you can pre-compose all of the layers apply your effect to all of them, then collapse transformations and the 3D spacing will be preserved as will any lighting, shadows, and camera moves in the main comp will still work.

The only time you want to use an adjustment layer is when you want to apply same effect to all layers below the adjustment layer. Sometimes I will throw Curves or some other color correction on an adjustment layer at the top of the timeline to make a global color grading change. Sometimes I will add an adjustment layer with other effects in a nested comp over a bunch of layers that I want to modify if there is transparency in the comp. They do have their place but you never use an adjustment layer with an effect that generates things like Gradient Ramp, Particle systems, or keying because it just doesn't work.

I hope that makes sense.

[Roland Kahlenberg]

An Adjustment Layer composites all layers below it into a single layer. An effect applied to an Adjustment Layer is applied ONCE to the composite of all the layers below the Adjustment Layer.

YOU ONLY NEED TO REMEMBER THIS SIMPLE RULE ON ADJUSTMENT LAYER.