Is the metering still set to spot metering? I would suggest trying different metering and trying the same experiment. If that makes no difference, I would then try shooting another series of shots in manual mode, in Jpeg and then in RAW, and using the aperture and shutter speed settings that gave you a correct exposure using the green mode. Make sure the camera is actually setting the chosen aperture correctly on each shot.

If the problem happens with Jpegs and not in RAW, this would indicate a fault with the camera. If the same results(ie differing exposures) appear with both RAW and Jpeg, it must be the lens that is causing the problem. If both RAW and Jpeg are OK in manual, then it could be the metering in the camera that is at fault.

Edited for (hopefully) clarity.

Were these shot as jpegs? If so, perhaps it could be something to do with the image processor in the camera? If it was on spot metering, the image processor may have tried to adjust the shots assuming that you were exposing for the centre of the frame, and then adjusted the exposure over the whole image to compensate.

+1!

You must have very steady hands...

That's what I found bizarre; that a ten quid objective can give such good results! Just proves that expensive does not neccessarily mean better.

Stunning detail, bizarre that you shot it on a Lomo lens and very surprising the amount of detail you got from the lens. Nice job you must have to be able to do this at work!

I wasn't sure I had an appropiate entry, but a quick look through some recent pics and it was immediately obvious which picture to enter. I also had a picture of some graffiti I was going to title "My first swear-word" but resisted the tempatation....

Has anyone on here actually bought one? If not then that would explain the lack of comments on it.

I have never owned a 12-24, but I had a Sigma 10-20mm, which I used a lot until I bought the 15mm Ltd. I now use the 15mm far more than the Sigma, partly because my wife has nicked the Sigma and stuck it in her camera bag! Sometimes I want something a bit wider, but I have found that I have adjusted to the 15mm, which I think is a fantastic lens. The compromise on focal length works for me as it's so light to carry around. I am not sure I would want my wife to sell the Sigma, though, it's nice to have the extra width sometimes.

Excellent macro shot, lovely and sharp!

Nice shots and nice bikes! The blue Kwaka.is my favourite, if you could get rid of that MCN sign it would be even better. I have rented Enfields in India a few times, they are still making them. They don't handle or stop very well but the engine sound makes up for it