I posted a similar response in another thread, with the user pasting images into Word, and my suggestions fixed his problems.
Your image(s) that you're looking at are likely proxies of the actual files - for instance, TIFF files have a lot going on and they're "multi-layered" image files - which include a very-low-resolution screen proxy, a representation of what the actual file is going to look like in order to keep screen refreshes reasonably fast.
I was dealing with this very question in the mid-90s with QuarkXPress. A dev created an XTension that better approximated the on-screen appearance of an image, but had no effect on the printed image - it was basically a placebo for users of QXP.
Print out your page, that's the real proof you're looking for. If the image(s) in question don't satisfy your needs, you should look to increase the resolution of your source file.
Don't ever judge your final document until you've evaluated the final source document. TIFF files are great for print files - on-screen files, there's better file types to use.