Luma Keyer

[Esam Rosado]

Luma keys provide a way to composite a foreground clip over a background clip based on the luma levels in the video. This is most often useful for still images, such as a picture of a logo over a black background, or computer-generated graphics. You create a luma key with the Luma Keyer effect.

Light Wrap: These controls blend color and lightness values from the background layer of your composite with the keyed foreground layer. Using these controls, you can simulate the interaction of environmental lighting with the keyed subject, making it appear as if background light wraps around the edges of a subject.

Edge Distance: Lets you adjust how close to the edge of your keyed subject the effect of the Fill Holes parameter gets. Reducing this parameter value brings the filled area of the matte closer to the edge of the subject, sacrificing translucency at the edges. Raising this parameter value pushes the filled area of the matte farther from the edge, potentially introducing regions of unwanted translucency within parts of the subject that should be solid.

Levels: Use this grayscale gradient to alter the contrast of the keyed matte, by dragging three handles that set the black point, white point, and bias (distribution of gray values between the black point and white point). Adjusting the contrast of a matte can be useful for manipulating translucent areas of the key to make them more solid (by lowering the white point) or more translucent (by raising the black point). Dragging the Bias handle right erodes translucent regions of the key, and dragging the Bias handle left makes translucent regions of the key more solid.

Black, White, Bias: Click the Levels disclosure triangle to reveal sliders for the Black, White, and Bias parameters. These sliders, which mirror the settings of the Levels handles described above, allow you to keyframe the three Levels parameters (using the Add Keyframe button to the right of each slider). Keyframing the Black, White, and Bias parameters may yield a better key, one that adapts to changing blue-screen or green-screen conditions.

Shrink/Expand: Use this slider to manipulate the contrast of the matte to affect matte translucence and matte size simultaneously. Drag the slider left to make translucent regions more translucent while simultaneously shrinking the matte. Drag the slider right to make translucent regions more solid while simultaneously expanding the matte.

Overlay: Combines the background layer with the wrapped areas of the keyed foreground layer so that overlapping dark portions become darker, light portions become lighter, and colors become intensified.

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There maybe times when you need to key a shot based on luminance. Well thankfully for Frdric Devernay he has developed the Keyer node to have 3 keying modes and 1 dispill mode. The keyer node has a luminance keyer builtin. It does a good job, but I was recently experimenting with another node not to many people use for keying. The HSVTool node is a great primary and secondary color correcting tool. It is also a hands down best keyer if you know what you are doing. This is also the same thoughts from the developer himself (Frdric Devernay).

The output alpha mode that I found to be successful for LumaKeying is the Brightness output. The HSVTool doesn't have a Key Lift and Key Gain like the Chromakeyer and Keyer nodes. So, I used something better which was the ColorLookup node. Everybody knows that in any 2D graphic/photo editing app, the curves tool is one of the most power tools in those programs and Natron is no different. The ColorLookup curves are amazing when you only need to adjust a certain range/tone in the alpha/matte channel.

Still, this is unsatisfactory. I would try deleting preferences to see if it brings things back to their right places (start the application holding down command and option keys and confirm when asked).

Nope, Luis, all of that SHOULD be in the Keying category. There should be 7 effects in the "Keying" category, all the tools used for pulling luma and chroma keys. You are missing the Luma Keyer for sure. That's is very odd and not a very good symptom. Not good at all, since these are not Motion built plugins, but coded and stored in System resources.

Here's what I'd do, a PITA, time consuming, but easy. Because I suspect you're soon going to have other things missing. Download FCS Remover from Digital Rebellion (dot com). Use it to TOTALLY remove FCPX and all traces of it from your system. Reboot, go to the App Store, to Purchases, "Install" FCPX. Then run the "Download Additional Content" function. Start over with a fresh install.

The Luma Keyer node uses the overall luminance of an image to create an Alpha channel. The label of this node may seem misleading since it allows pulling mattes from almost any channel. In some respects, it is more accurate to call this node an all-purpose channel keyer, but its primary purpose is for extracting alpha channels based on luminance

Threshold
This range slider sets the lower threshold using the handle on the left and sets the upper threshold using the handle on the right. Adjusting them defines a range of luminance values to create a matte.

Clipping Mode
This option determines how edges are handled when performing domain of definition rendering. This is profoundly important when blurring the matte, which may require samples from portions of the image outside the current domain.

Gamma
Matte Gamma raises or lowers the values of the matte in the semitransparent areas. Higher values cause the gray areas to be more opaque, and lower values cause the gray areas to be more transparent. Wholly black or white regions of the matte remain unaffected.

Solid Matte
Solid mattes are mask nodes or images connected to the solid matte input on the node. The solid matte is applied directly to the alpha channel of the image. Generally, solid mattes are used to hold out keying in areas you want to remain opaque, such as someone with blue eyes against a blue screen.

Garbage Matte
Garbage mattes are mask nodes or images connected to the garbage matte input on the node. The garbage matte is applied directly to the alpha channel of the image. Generally, garbage mattes are used to remove unwanted elements that cannot be keyed, such as microphones and booms. They are also used to fill in areas that contain the color being keyed but that you wish to maintain.

Garbage mattes of different modes cannot be mixed within a single tool. A Matte Control node is often used after a Keyer node to add a garbage matte with the opposite effect of the matte applied to the keyer.

Post-Multiply Image
Select this option to cause the keyer to multiply the color channels of the image against the alpha channel it creates for the image. This option is usually enabled and is on by default.

Deselect this checkbox and the image can no longer be considered premultiplied for purposes of merging it with other images. Use the Subtractive option of the Merge node instead of the Additive option.

I have been messing around with using a luma key to key out the brightness of the saber. I turn that into a matte and use the matte on a copy of the base footage. I then take that copy of the base footage layer (with the lighstaber matte applied to it) and use the levels tool to brighten the saber even further so that it is the brightest part of my scene.

I then put an adjustment layer above the whole comp and use Red Giant's Optical Glow plugin on that layer. I turn up the "highlights only" to around 95% so that only the blade glows. This makes a very fast and easy lightsaber effect as long as the saber is the brightest part of my footage to begin with.

The green saber color is very green as well so I can also key it out using primmatte keyer or similar chroma keying effects; however, I would love to have proper exposure on these lightsabers like in the Sequel Trilogy. Lightsabers are no longer extremely bright lights with colored falloff, they now feel more properly composited into the scene with even the white parts being slightly more tinted to their color. I want to match this look while somehow keeping the quickness and ease of the method above.

Does anyone know of a way to apply glow or a similar effect to just one color channel? For example, can I key out the green and then make only the green channel glow while keeping the proper exposure because sometimes the blade does not have the bright white core in the center. Sometimes it is a subtle white, with more of the green showing through.

You isolate channels using channel effects like Shift Channels/ Set Channels and Channel Combiner and that's also the way to re-combine them short of using blending modes like Add. That's pretty much all there is to it. The only real issue is that you easily end up with tons of layers since due to how AE works you need one layer for each channel. and that's probably where the wheels will come off your quick & dirty method - it's not going to work this way and you have to put in much more effort

You isolate channels using channel effects like Shift Channels/ Set Channels and Channel Combiner and that's also the way to re-combine them short of using blending modes like Add. That's pretty much all there is to it. The only real issue is that you easily end up with tons of layers since due to how AE works you need one layer for each channel. and that's probably where the wheels will come off your quick & dirty method - it's not going to work this way and you have to put in much more effort by creating all the necessary pre-compositions.

I want to build a circuit which uses a comparator to switch a mux (currently looking at LMH6574) between two different inputs. One input is a camera which outputs CVBS, and the other is a vintage Leader LCG-400 pattern generator. I want to have both the camera and the composite output of the pattern generator going into the multiplexer, apply a comparator to one of the signals, and use the output of the comparator and a little bit of discrete logic to switch the mux within the current line of video to do luma keying.

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