If somebody can explain the how, why etc. for this problem. Every time I take pictures in low light at f/4 I get vignetting but not at higher f stops???
Here's an example. These two were taken at 4:30am at ISO 100, 12mm. One is at f/4 and the other at f/11
For me the whole idea of a fast f/stop is to be able to shoot in low light. But???