In October, thousands of Snow Geese are seen in the Vancouver area on their migration to points further south. We were experimenting with a mirror lens when a flock passed overhead. Several exposures were made, but the lens has a very shallow depth of field, so most were too fuzzy for our liking. This particular picture, however, is nicely sharp and shows that the lens does do a very good job. Capturing birds in flight is tricky and anyone attempting to do this should expect a low proportion of good images.
For those people interested in digital cameras, the 1600 x 1200 image of this picture has the original, unprocessed pixels cropped from the camera's image file. The only difference between it and what we have on our computer is the JPEG compression (the red channel has been blurred in the sky areas).