It's better not to think it, but say it. In loud and confident voice. Make a verbal command basically - any phrase that mean increasing clarity and vividness would work. Also as a good verbal command work spells, like you know, from Harry Potter If it's too dark, imagine wand in your hand (if manifesting things is hard just pick any stick, brush, pencil, anything that looks like a wand) and say "lumos" or "light", "brighter" or whatever word you put this sense into. It may sound a little silly, but it works!
Good luck!