I've started having this intermittent issue on my Nikon Df.
Occasionally (1 out of 50 shots?) I take a photo but the viewfinder goes dark and doesn't re-open.
When i press it again it re-opens. The photo still captured perefectly.
initially i thought this was a lens issue but it's happening with different lenses so likely the dslr.
does anyone know what it is exactly and best place to fix it (refurbished out of warranty)?
So for some clarity, when you look through the viewfinder, you're looking into the prism bounced of a mirror inside of it, then down to the big mirror that you see when you take the lens off.
When you take a photo, that mirror bumps up out of the way, and the shutter fires, exposing light on the sensor, then the mirror returns "home".
So.. it's a "mirror returning home" issue that you are experiencing.
Are you using after market batteries or does this only happen when you use a specific battery (if you have several?) or when battery is low on charge? I experienced exactly the same issue on a D700 with one battery when it hit about 30% charge. I see no logical reason for this to be the culprit, but I'm convinced after much testing that it was.
Based on the information you have provided so far, the shutter seems to be okay: photos are being taken without a problem, even if the viewfinder "goes dark".
The problem appears to be with the mirror, which is responsible for redirecting the light from the lens into the viewfinder, thus giving you a picture there. Normally, it swings up whenever you press the shutter release to allow light to fall onto the sensor. It seems like it is "hanging" occasionally and does not swing back into its normal position, thus the "missing" image in the viewfinder.
You may want to take the lens off your camera and take a few shots until the viewfinder problem occurs again, then look into the camera; if the sensor is visible, then the mirror problem is confirmed. Maybe you can also see what's keeping the mirror from returning to its original position.
The rest is up to you: if you feel comfortable around taking cameras apart, feel free to grab a screwdriver and get to work! ;) Otherwise, you may want to seek a certified Nikon repair shop or a free one. Either way: Best of luck with getting it back to work!
I have the same problem. It is a mechanical problem of the shutter release. The cause is that the shutter button does not return to the top. It sticks in middle position, like it has some dirt inside. Please look carefully at your shutter release buton when the problem occurs.
When it happens to me, I try to blow it with air, but no result.
Maybe it should go for service to Nikon shop.
This is the mechanical problem. Shutter operating motor's gear may be cracked. It should go for service.
