My artists have created greyscale textures that only really have 2 channels of information - luminance and alpha. In the past, I would have easily loaded this into OpenGL, etc. as a Luminance_Alpha texture. Is there a way to do that in unity? It seems a big waste to expand these textures out to RGBA as it unnecessarily doubles the memory usage.
Thanks!
So it’s a greyscale/alpha image ? Shaders can handle that easily.
Check your import settings : Select an image file, import settings opened in the inspector. Set texture type to “advanced”. Apply. Enjoy !
(looks like you particulary want the “format” parameter at the very bottom of the inspector)
Setting the texture to “advanced” alone doesn’t really accomplish anything unless you are implying it will unlock some 1 or 2 channel texture format. 
I am quite familiar with the ability to specify a Texture format, however the only choices I find (regardless of platform) are variations on RGB, RGBA or Alpha8 formats. What I’d like to have is a TWO channel format, e.g. the LuminanceAlpha or RedGreen format seen in OpenGL or OpenGLES. (eg: Red Green Texture Compression - OpenGL Wiki)