Here are a few images of an Eastern Tiger Swallowtail Butterfly from our visit to Davidsons Mill Pond Park. The featured image is a single image shot with a Canon 300mm f/4 lens with a 2x teleconverter on a Canon 7D @ f/11. Image below was a Blend of 2 stacked images, blended in Photoshop with a soft edge on the seam. Field of View equivalent with the Canon 7D (1.6x crop camera) 300mm f/4 lens, Canon 2x teleconverter ~ 960mm. When using a 2x teleconverter your lens wide open will be @ f/8, not f/4 because you loose 2 stops of light with the 2x teleconverter. So I usually stop down at least 1 additional f/stop to help with sharpness because of the added teleconverter.