Last week I was developing a test roll of tri-x and was surprised to find that on several frames, 4 consecutive, there appeared a vignetting effect. Each of the four corners of the frame had a white area of overexposure/overdevelopment. The rest of the roll was fine except for the last two frames which showed the same effect. I am at a loss as to why this has happened, and in an apparently inconsistent manner. I was shooting with a Nikon Fe, never any trouble, Tri-x 400 at EI of 320 and developed in a single tank of T-max with a 20% more development time of 7min 15 seconds.(posted 8551 days ago)