How to Take a Good Butterfly Picture
Butterflies are obvious picture subjects. Even people who don't ordinarily like insects can't help spending a moment trying to capture the pretty colors and patterns of these distinct creatures. Here are some of the things I do in my attempts to get the perfect shot.
First off, your primary goal is likely to capture the wings clearly and in sufficient detail so that the intricate patterns are visible. More often than not, the wings will look better if they're open instead of closed. Either way, the best technique for ensuring that both wings are in focus is to line up the plane of your camera with that of the butterfly's wings. Even being slightly off can result in the tips of the wings being out of focus.
Another complication is that while you're busy trying to get the wings in focus, you may lose sight of the body and head areas. To remain pleasing to the eye, the "head" of the butterfly needs to be in focus too. Otherwise it'll be too distracting. You can improve your odds of getting all these parts in focus by decreasing the aperture.
The problem with too small an aperture is that the shutter speed could end up being quite slow. If you're using a zoom you'll want to make sure the shutter speed remains above 1 / field of view e.g. if you're at 300mm then the shutter should be at a minimum of 1/300 for handheld shots. Anything less, and you'll introduce motion blur.
Finally, your approach towards the butterfly can make all the difference. The best opportunities are when the butterfly is on a flower drinking nectar. This acts as a distraction, but also increases the chances of the butterfly returning should you scare it away. I get my camera ready with all the settings I want for the particular situation. Then I slowly walk towards the butterfly. If I scare it, I stop moving until it returns to the flower. I'll also take shots as I approach in case I don't make it to my ideal spot. Once I'm in position, I crouch or kneel to get my camera in to the right spot and then start taking pictures.