Expedition Blues: ARGB in an RGB world

So, this will likely seem rambling and incoherent as I barely understand what I’m thinking about enough to form it into questions.

After working a few years in the LZX RGB world I feel like I’ve gotten my head around most of the conventions and workflows at play in the Expedition line. Then Memory Palace came into my life. Granted, it’s in the Orion line but it has me pondering the possibilities within the Expedition workflows. That A input prepended on the RGB inputs have thrown me for a loop and I’m interested in learning more about using it wisely in conjunction with LZX Expedition modules.

The Expedition line seems to be all about RGB flows with Staircase, Mapper, and Bridge as examples of modules that can use one signal to turn into a trio. Polar Fringe, Color Chords, Marble Index, Bridge, and Passage all seem to lean towards an RGB workflow when looking at inputs and outputs. The only module pre-MP which seems to have a fourth option (similar to the A on MP?) as a possibility is Visual Cortex with Luma output, and Colorize input on Channel A.

So my questions:

-is it inaccurate to think of ARGB as an extended RGB workflow? I think I naturally mash them together in my mind because they both have RGB in their names.
-what sort of signals does the A part enjoy feeding on? I’ve randomly plugged a few things in my explorations but don’t feel like I’ve hit on anything significant yet. I’d really love a workflow idea using a signal from the Expedition line effectively with it.
-can anyone recommend some reading material to help me better understand core concepts of how ARGB has been used historically and how its being used currently?
-generally is the A input more useful in a processing environment (camera, player input), or a generative (ramps, other shapes, and pattens) environment? Both? Neither? Something else?

Thank you for any tips and tricks you care to share.


ARGB is simply RGB with an additional input for an Alpha channel. This convention was invented (I believe) alongside Photoshop to give digital film compositors a way to carry transparency information with their images. Digital image formats like PNG, TIFF, and others have alpha channels. In the digital realm, it is usually represented as RGBA or sometimes referred to as a 32 bit image.

In LZX land, you can think of it basically as being the same as RGB, with an extra input to control opacity. The A input on the MP operates very similarly to the Opacity VC input on the Marble Index. Make sure the MP is set to Alpha key mode, and experiment with different ramps in the A input to start. Put a Doorway before the A input for more precise control.


I grew up with the Photoshop way of thinking, so I tend to think in A, and have to learn to think in ‘key’. It’s interesting to see the other way! :smiley:

I would explain things the same way that Johnny did.


To your last question, you’ll only see Alpha show up when you’re combining signals (VC, MI) with some sort of opacity related control; foreground/background, channel 1/2, like that. In the Memory Palace, you make use of it when you write into the buffer.

If you consider the 0-1V signal that is some video (an image? a shape? oscillations?), then when used as an alpha channel / opacity, where the signal is ‘on’ the most (1V, right?) then you will see the RGB signals associated with it, and where it is ‘off’ (0V, right?) then you won’t see the RGB signals. For all the values betweeen 0 and 1, you will see (RGB)*A worth of the RGB signal, so lighter closer to ‘off’. Hopefully that makes some sense.


I like johnnys response.

But in my words, (in current functionality) you can set the key to Alpha mode as stated above. and now instead of keying the input image you have a secondary input from which your key will be derived.

So in luma mode… you put a signal into RGB and then the memory palace keys THAT signal. and the threshold set by Center and Width will provide the feedback we are expecting. so if you plug in a camera to RGB you can key out certain parts of that camera image and the surrounding image will feedback into that space.

However in Alpha mode. you can put a camera signal into RGB. but instead of feeding back based on the camera you will feedback based on the signal in the alpha. Important to note is that the ALPHA input is a video rate input. so you can put as complex a signal as you want there.


I’m also really loving patching through Curtain to the MP alpha input when alpha keying. This in addition to the Softness slider gives you a lot of fine opacity control over the MP foreground.

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