Noise spots on long exposures
Long time reader, first time poster... with a big thanks to the community.
I own a Sony Nex 6 and noticed that long exposures show blemishes that are not visible on short exposures (see picture). I don't know when this started, but it wasn't always the case. Also, I'm quite sure it occurred with several lenses, so the issue seems to be with the camera. I used the built in sensor cleaning function, but to no avail. Any ideas as to the reason and what I could do about it? Going for a short trip to Acadia this Sunday and hoping to have it fixed by then.
Here's an example - you'll see it especially in the sky:
|Chicago Alley by tko|
from Down the alleyway
|Callan-5680 by vbuhay|
from What Child's Dream May Come
|Widget by Wilfried HKG|
|Oxbow Bend by stickpointed|
from Landscape - Colour #2