Composition- subject isolated pretty well. Too bad the the butterflies wing blurred into that front part of the fence. Background- Good except for as noted above. Technical-seems to be "chopped in half both horizontally and diagonally. Overall Impression- I like the subject, meets the challenge, some technical issues.
Difficult shot. Always got to get the bugs before they go away. I wish I could see more of the butterfly's head. Like the depth of field. the dark portion of the building up in the UR corner draws my eye a little bit. I think the best comment I can make would be to have shot from the other side of the fence -- obscure the back side of the butterfly, but not the head. Maybe use a piece of white paper to bounce a little light onto the b's wing.
I love the clarity of this picture... right down to seeing the spider webs and (morning dew?) in the top of the fence. My only grumble is that the butterfly doesn't quite stand out enough...
Nice shot! I am glad you didn't zoom in much tighter on the butterfly... the other objects in the photo give good reference to the butterfly being upside down :)