Depth of field with long lenses and two subjects

Song sparrow, Juvenile white-crowned sparrow, and adult white-crowned sparrows at Munson Pond.

Many times when photographing birds, I will find more than one in my viewfinder.  A single bird is always relatively easy to shoot - focus on the bird (head if possible) and press the shutter button.  But what do you do when there is more than one bird?

You basically have three choices.  You can focus on the closest bird, focus on the farthest bird, or focus on a point somewhere in between.  The best choice will vary a lot depending on the exact situation, but there is, I believe, a good general first choice.

The best, general first choice is to focus on the closest individual.  The reasons are as follows.  

• the front individual will be larger and therefore have more detail than the individual(s) behind it.
• depth of field is so limited (I used a 500 mm with a 1.4x TC on an APS-C camera to give me a relative focal length of around 1000 mm) when shooting wide open with a long lens that you may get one or the other in focus, but rarely both.
• the first subject in focus with a blurred background one tends to look better than the last subject in focus with a blurred foreground one.

The truth is that each of these reasons can be argued against in the right situation.  Pixel count may not be significantly different.  Higher apertures can be used or the individuals may be close enough together to render any focus differences moot.  Sometimes, it is the rear subject that may be more desirable, especially if it is a more interesting species or shows a more interesting behaviour.

It doesn't hurt to shoot all options and play with the results later.  You can see the image above compared with the same photo having the rear bird in focus.  Which do you prefer?

Left: Front WCS in focus, rear blurred.  Right: Rear WCS in focus, front blurred.  Which fo you prefer?

Thanks for reading.

Eric Svendsen     www.ericspix.com