てもいいですか and できますか

てもいいですか

Focuses on permission (is it allowed?)

ここで写真を撮ってもいいですか？
May I take a photo here?
Asking if it’s allowed to take a photo.

Focuses on feasibility or ability (is it possible?)

この写真を撮ることができますか？
Can you take this photo?
Asking if the person is able to take the photo. Maybe they don’t have a camera, so they can’t take it.