DSLR sensor mystery - help!?

Question

I have had a Nikon D3100 for about 3 weeks now. I have only ever exposed the sensor a few times when changing lenses and have been very careful to not get dust onto it. A few minutes ago I looked at the sensor under a bright light to see if any dust was present and I found a rather large fingerprint! I bought the camera brand new from my local store (Wilkinson Cameras) and have NOT put my fingers anywhere near it. I really do want to stress that I have NOT touched the sensor and nobody else has even used it except me. How is this possible and what should I do now? Please shed some light on this mystery, thanks!

Answer 1

As you have realised, its the mirror not the sensor you see when changing lenses. How the fingerprint got there is, as you say, a mystery.



You have 2 options;



- take it back & demand a professional clean



- do nothing (the mirror is what directs what the lens 'sees' to your eyes at the viewfinder - it flips up out of the way when the image is taken) - if the viewfinder image is prefectly ok, ie able to see focus, then it's not affecting it.



Do NOT try to clean the mirror yourself. The mirror is silvered on its top surface (not the bottom, like an ordinary mirror) and brushing it with anything abrasive can cause the silver to come off.

Answer 2

One clue will be how does the fingerprint show up?



If it's one of those fingerprints you see on police records the only way it could have got onto the sensor is when the sensor was out of the camera. Unless the person was remarkably double jointed. This should be something that the store will do something about.



However an end on finger print suggests that somebody has touched the sensor after manufacture. This make the situation more difficult, as this could be anybody. Speak to the store to see if they can do anything about it. If they can't, it's time to buy the sensor swabs and eclipse.

Answer 3

The fingerprint will have no affect on your images. The mirror reflects what you are focusing on to the CPU and viewfinder, the mirror flips up to expose the sensor when you take your shot. I am sure that the store where you bought it will clean the mirror for you, although it should not be there on a new camera, it is no big deal and very easy to clean.



TOM

Answer 4

Id give them a call or email them just saying only you've had access to the camera and point out you have noticed a fingerprint on the sensor as its not something id like to touch unless something like light dust that could be blown off maybe.

Answer 5

Just note that it's quite certainly the mirror, not the sensor, that has the fingerprint. You cannot see the sensor when you're exchanging lenses.