If your tv is a crt and the brightness control up front doesn’t help there is most likely a knob on the inside that will solve your problem.
It’s usually located on the Flyback transformer along with a Focus knob.
Keep in mind that there is 20,000 volts or higher inside a CRT television set so if you trek to resolve your issues with it, be careful. ; )
I’ve got it as bright and light and contrasted as it will go and I’m afraid to go inside it, especially now. ha. But thanks