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I run an online shop and I have been using Nikon 3100 for many years. Recently I started to notice that in all the pictures the right side slowly gets dark and there is a dark slit almost look like a vignette on the edge. I knew there were something not right but I could still use photoshop to solve that problem.
But all of sudden all the pictures are looking like that since yesterday. I use two strobe lights and manual mode to take studio pictures, strange thing is the shadow only appears in that circumstances. The pictures are absolutely normal when I use the other modes. My shutter speed is 1/250.
Can anyone tell me what’s wrong with my camera? Is it the shutter?