When you're taking reference photos for paintings, it's important to remember that they're just that, for reference, not to frame and put up on your wall. So it doesn't matter if the scene isn't absolutely perfect, if it's overcast rather than sunny, if there are trees where you don't want them, or a hideous fence cluttering up the foreground. As the artist you're free to move elements around, to leave things out, and put others in. Give a group of artists the same reference photos and every one will paint a different painting.
Take this beautiful landscape photo of the St. Joe River drainage in northern Idaho, which is part of the Landscape Reference Photos Collection. Sally Stratton, who took the photo, said she wants to paint it in watercolor and acrylics. I think it'll make a glorious landscape painting, with those rows of mountains marching off into the distance.
If I were to paint it, I'd tweak the composition a bit, moving the large tree to the right so it's not quite so central, and making it a little taller, so it reaches further into the sky rather than just topping the last bit of mountain.
There are two ways I could go about it. Either I could work out the altered composition in a sketchbook or on a canvas, or I could use photo-editing software to alter the photo to get an idea of the final result, like this...
