I wrote in “Male and Female Red Winged Blackbirds” :

Even if birds are resting, they can take off suddenly. So I make sure shutter speed is above 1/160 sec. If shutter speed is below that, you may need to raise ISO.

So, I checked with my old seagull images.

Shutter Speed

Here is an example shot with shutter speed 1/160 sec.

ƒ/5.6, 1/160, ISO 200, focal length105 mm 

seagull13_ 051

I like showing wing motion. But I wish had set a larger number f-stop of 8, so I could have focused on the eye.

The larger the f-stop, the smaller the aperture. The smaller the aperture, the greater the depth of field. With a greater depth of field, more of the bird comes into focus.

The seagull below has almost the same pose as the one above. But since shutter speed is much faster (1/500) than the seagull above, the wings are frozen and this seagull looks like a statue.

ƒ/5.6,1/500, ISO100, focal length 225 mm

seagull12_ 19

Can you guess why the second seagull’s whole body is focused  despite the same f-stop as the first one? 

Aperture

The answer to the question above:

  • The first gull’s head to tail is not in a same plane.
  • The second gull’s entire body is in the same plane.

Aperture diagram

The larger the aperture, the smaller the f-stop number. I wish they had made it the opposite. It would have made more common sense.

If I were using a wide lens, for example, 16-50 mm lens, the first seagull would have focused from head to tail, but I used a telephoto lens (focal length 105mm).

With longer focal lengths, you need to close the aperture (increase the f-stop) to focus the entire subject.

 

Note:
Camera setting info of seagull header image:
f/7.1, 1/250, ISO125, 125.0 mm