GRD4 Snap Focus Mode

I'm starting to get a bit more used to the controls on the GRD4 - snap focus seems a good mode to have as it allows you to manually set a focus distance. I tend to leave it set to 2.5m mainly, but there is also 1.5m, 1m and even 5m & infinity.    This picture was taken with 2.5m snap focus, but I notice the edges seem more out of focus than the centre with this setting.   I will have to try out the other snap distances of 1m & 1.5m, as I cannot see much point in anything over 2.5m with such a short focal length. I would imagine that most people would tend to use snap focus for shooting closer things, rather than houses across the street, but it's interesting to see the effect of using this mode to shoot more distant objects than the quoted snap distance.