How to get a smooth background on a bird image? In brief,
1. Get low. Getting low puts the angle of the focus plane completely off the focal plane. In this image, I was level with the background, and could go no lower, based on the terrain (a boardwalk).
2. Shoot long. The longer the focal length, the easier it will be to blur the world. However, in this image, the I was using my longest focal length.
3. Shoot wide open. With my lens and TC combo I was using (300 2.8 + 2x TC), I like to stop down a full stop to give me better sharpness. Also, the large birds can end up rather out of focus in the wrong parts with too broad an aperture.
4. Position the background as far as possible from the subject. The subject was flying to and from an area where he was gathering sticks, and flying his pattern rather regularly. There was no perceivable way to get him farther.
5. Get as close as possible to the subject. Remember the boardwalk? This was as close as I could get.
6. Post processing. Once the image has been captured, it is possible, and often quite desirable, to render the background more out of focus in the post processing stage. This was not done on this image, however…
Because I actually like the background! The vegetation and water provide an excellent frame for the bird with the curve they make as they meet. The out of focus vegetation is still recognizable as vegetation. The bird’s natural environment is shown here. However, I do not like environmental context for all images all the time. This is art; there is no crime in processing or not processing. The decision is the artists’! The paint is photons and a sensor, as well as some digits in binary. In making the decision of how to process, the goal is not to simply copy what is vogue, but to deliberately select exactly to create in the final image, to express the message desired.