Establishing a scale, in other words. "Sky" is a poor reference -- especially at night but consider dusk or dawn where it's in the middle of range of light-to-dark.
My experience of digital camera photos (esp. "RAW" photos, similar to film negatives) often starts with the range the camera acquired. THEN you process to full bright, full black, and the treatment of the range between. (I'm not going into HDR here...)
And yes, "I have a visual" indicates a preference for a traditional pixel-by-pixel (or equivalent analog) signal wth scan-line and frame delimiters. Not sure how that works under compression schemes...
More advanced compression schemes might eventually prevent signal recognition, not because of signal strength, but because of a lack of recognizable repetition.
It would be as if a modern computer screen image were being transmitted to an old black and white Emerson with a mineral screen.
If the signal is intended to be received by others, then it should be decipherable. You can see some of this displayed in some science fiction shows as a highly pixelated image becomes sharper as more information fills in the decompression algorithm.