Over the past couple of months i have been noticed a thick bold line on some of my images and when using my Canon M5 and 50mm f1.8 stm lens. Please see below the sample photos the first is taken with my M5 and the second with my 600d There is no white line on any of the images that i have taken with my 600d. The sample images were both taken about a minute apart and using the exact same shutter speed, iso and apeture. It is also the only lens that does this with my M5, i use a 24-105mm regularly and have no issues with image quality, Does anyone know the reason as to why this could be happening when using my 50mm?
looks to me more like a light leak? you could try putting a cloth over the connecting flanges to rule out that, also try using a piece of paper to make an extended lens hood and test, again to rule out front lens flaring but it really doesn't look like that, what does the rear element look like on the lens in question? can you compare it to any others, etc not really sure on this myself, just a few ideas.
I think you need to make more comparison shots under better lighting conditions, the first one shows overcast lighting whereas in the second the lighting is much brighter and you have shadows on the grass. Your problem could be an internal reflection in the camera body, to rule this out take one normal shot then another with camera upside down. If it is a body problem then the thick line will move otherwise it is a lens or lighting problem.
