Getting rid of colours in textures So continuing from my many Earth posts, I've now come to the dilemma of my night side. I'm currently using a texture that's around 52000x32000 which is perfect, can't go lower than that, and it was pre stitched together, however, the land is dark blue. I want this to be completely gone with just the lights showing. I remember seeing someone post on Blenderguru's Earth tutorial that they managed to do it but they couldn't remember the process.

Is there any chance anyone out there would know how? Rule out photoshop or finding a new texture as I've tried both. Other textures online are either of a lower pixel density or need stitching which my computer can't handle. I've tried removing the darkness and keeping the lights in photoshop with the already stitched image but my computer can't run it with such a high amount of pixels.

I've also tried messing with the image adjustments within Blender but have had no luck.
The RGB Curves node sounds like what you are looking for. It functions almost exactly the same way Photoshop's curves command does, so it is very useful for pushing light and/or dark values.
See the image below for a quick example, where I left lighter colors (on the right) more or less unchanged, but drastically darkened anything below about the halfway threshold.

The RGB Curves node is also handy for tweaking the exposure levels of a background photo/HDRI without having to modify the original file.