Black line or darkened horizontal edge of images

Hi Everyone

I'm a newbie to the SLR World and recently have been having problems with my D3100. Every so often the blue sky would appear in a dark and then a light blue tone (almost as a distinct line) along the horizontal axis. Now this happens on almpost every shot, not just landscape shots, but in some shots a thick black line appears along the edge of the image as well. i have been travelling for the last 4 months and the camera has taken a little bit of a beating, as I have been taking it trekking etc, so I'm not sure if I've done something to the lens to make it do this?

I have attached examples of the problem below.

The first image specs were:
Exposure - 1/320 sec at f / 9.0
Focal length - 32mm
ISO - 100
Flash not used
Lens - 18.0-55.0mm f/3.5

Second image
Exposure - 1/250sec at f/8.0
Focal length - 40mm
ISO - 100
Flash not used
Lens - 18.0-55.0mm f/3.5

Has anyone else come across this problem and know how to rectify it?

Thanks in advance
Loz

I'd say that it looks like you may have a shutter problem. But whatever it is, you need to take it for repair.

Sorry, but this looks like the shutter is sticking occasionly. I cant see as can be anything else

Try to take photos in similar conditions in shutter priority mode and do a few shots in different exposure time to see if the horizontal line disappear or gets worse.

You could try sticking it in manual set at 2000th sec, set on high speed frames per sec, and waz off a hundred shots or so. It could just free it up.

Hey guys

Thanks so much for your responses. I think it is the shutter because I did as per Dr Daniels suggestion and the lines don't appear in shutter speeds slower than 1/8 sec. Westmill i also tried doing as you suggested and the problem is still there.
Is a sticking shutter something that can easily be fixed? And is it something that I have done to make it stick? (eg dust, damage or touching the mirror in the camera accidentally?? Or just wear and tear?
Thx

Well it like you said... it had a tuff time. It could be a number of things. Its impossable to say without taking it to bits.
Its quite poss you may have a bit of dirt or grit in there, which is why i hoped that some fast firing might dislodge or
wear it down. Its certainly a job for the experts. It needs taking in.
Or set your camera to a slow speed and take it in for a part ex :smile-new:
Ive no idea what they charge for fitting a new shutter system. Your best bet now is to make a few phone calls.
Sorry it didnt work... but it was worth a try !

this will be helpful
Issue with a Horizontal Line in Photos - Nikon D3100 Forum