Can you see dust when you put your camera to your eye? If you do, you are not alone! First and foremost, if you can see dust when you look through the viewfinder, IT’S NOT on your sensor! Next, No, you won’t see it on your photographs. And yes, it can be annoying. When I received my brand new D4 when it was first released, it had a bug. I mean a real bug, a six legged little dood that I saw walking around in my viewfinder on the screen after my first shoot. It disappeared but not before it left a little stain on my screen. It drove me nuts! When there is dust on the TOP of the viewfinder screen (or bug stains), your only real option is to send the camera in to have it cleaned.
Viewfinder screens can’t be removed by us mortal folks. Now, you can take a can of air and blast it through the side crack of the screen but more often than not, it just moves it around. It doesn’t go away. Dust on the bottom of the screen though is the most common. You can use a sensor dust brush just like you would use it on the sensor to clean the bottom of the screen (do not use fluid of any kind). You might also want to brush off the mirror with a clean brush. Now with that all said and done and the screen is all cleaned, don’t be surprised if it instantly doesn’t reappear over and over again. The viewfinder screen is plastic and dust likes to stick to it. That mirror flaps up and down, a lot, and that will move the dust right back on the screen no matter what you do. What I do is, unless a bug makes a stain on my screen, I do the best I can to keep it clean and then otherwise, ignore it. It just goes with the territory.