The first two are beautiful....love the lighting on those. I also like the 3rd one the green is so rich looking, and that would be due to the overcast sky. So technically I don't think your sky is over-exposed. If you had exposed for the sky the grass would have been under-exposed. I'm not sure what type of filter, if any would help with this sort of situation, I'd be interested if anyone else can come up with something for this. Since I like to shoot on overcast or rainy days I often have the same problem.

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