Can't see whole image thru viewfinder when len is on

A rangefinder is a camera that has a rangefinder mechanism. This is a device that measures subject distance. Through this device, you see two images. When the two images coincide through moving the dial, the correct distance is displayed. On older cameras, this was a separate device and one must transfer this to the lens.
Now they are built into the viewfinder. You have different viewfinders for different focal lengths (zoom lenses are difficult, as a result).
A viewfinder is what the photographer looks through to compose, and in many cases to focus, the picture. Most viewfinders are separate, and suffer parallax, while the single-lens reflex camera lets the viewfinder use the main optical system.

I found this camera available for purchase as brand new for $450. Spending nearly $300 to repair an older version may no be a wise choice. You may find there is a market for the camera in its current non-working condition on eBay.

With that said, to your questions. 1) It will be difficult to diagnose without seeing it, but I have a suspicion in mind.

The viewfinder picture is actually what the lens sees, bounced up via mirror to a prism that projects the image to the viewfinder. If the mirror has become dislodged and is stuck in an odd position, the image would not be projected in the viewfinder. You can see the mirror when you remove the lens from the body. The mirror should be centered in the opening but at about a 45 degree angle. If it is loose or otherwise in the wrong place, this could be the problem. If the mirror is stuck and preventing the image in the lens from projecting on the sensor (behind the mirror) no capture will be possible. Other than the optics inside the lens and the mirror, there are few parts that could obstruct the image in the lens from reaching the viewfinder. Is the aperture of the lens open? If not, there may not be enough light to see the image in the viewfinder. This would also indicate that the lens is not opening up to let you see, and may not get set to the correct aperture when taking a picture. The camera usually opens the aperture to allow you to have a nice, bright image in the viewfinder. When you press the shutter release, the lens stops down to what the program says (or your manual selection) and the mirror lifts up out of the way, and the shutter fires.

2) Can you fix it? Maybe. Again, without seeing it - its hard to know for sure what the problem is and I don't know your level of skill either.

My suggestion is to bypass the camera shop that "doesn't know what the problem is but will fix it for $270" (how is that even possible??) and deal directly with Olympus USA Service and Support by phone or email to get an estimate / factory trained tech perform the repair.

Good luck!

There's a diopter control just to the right of the viewfinder. Adjust it while looking through the viewfinder until the display is sharp.

Two possible situations. It might be that the lens focusing system isn't working. Try focusing by hand (turn the lens manually) If the image moves through a point of sharp focus, then you have a lens or focus motor problem.
More likely, you have improperly adjusted the diopter. There is a small, circular wheel on the right side of the viewfinder, toward the top corner. It is sometimes covered by the rubber viewfinder hood so you might not notice it. This adjusts the diopter correction in the viewfinder and if it's set wrong, nothing will ever look in focus. The pictures would be fine, but since the diopter is a correction for your eyesight, the viewfinder will be out of focus.

The finished image looks dark or it looks dark in the viewfinder?
If your question is "the image looks dark" in the viewfinder my answer is it's an F4.5 lens so letting less light into the viewfinder and it will look dark. The big difference will be seen if you are coming from lets say a Nikon 50mm F1.8 which is two stops faster then your F4.5.
If it's the finished picture after you taken it I'd say you underexposed the shot.

Sounds to me like the aperture diaphragm on the lens is stuck in a small opening position. If you detach the lens from the camera and look through it, is the whole opening light or just a small dot in the middle? The diaphragm can stick if it gets a drop of oil on it.

It could be either aperture is stuck or ccd imager chip is defective in your camcorder that will be replaced.
In bright light, look into camera lens, turn ON in camera mode and observe does aperture open like an eye?
If you notice some thing opens right in center of camcorder lens then aperture is working and ccd imager chip is bad that will be replaced.
Let me know model number of your Sony camcorder to provide you ccd imager part number info.
Thanks.

I'm unfamiliar with the F80 but on models like the f65 and f75 the viewfinder screen has an lcd overlay and when the battery is exhausted or removed the viewfinder goes dark and blurry.

Looking at a picture of the f80 it looks like it's just an update on my f75 so it strongly suggests that you just need to insert a fresh battery. The lcd does draw power from the battery even with the camera turned off.

I hope that you found my answer useful, once you've tried another battery to confirm what I've suggested I'd appreciate it if you return the favour by rating my answer.

Please also ignore this answer, (see askers comment above). I've only posted it so that this question doesn't continue to appear as an unanswered one.

If anyone else has this problem please go to
http://www.fixya.com/support/t2637498-image_nikon_f80_dark_cloudy
for an answer.

Wow, that is strange. Is there a reset button or procedure, like holding power and exe or some other key combo in the manual? I had a C-5050 that would boot to a picture of a girl, not the normal Olympus splash screen, couldnt figure that one out either. Good luck, let me know if you give up on it or need more help..pishta68 at hotmail.com