Photo and Video Tips and Tricks

Using Selective Focus to Eliminate Foregrounds

Every (good) photograph has an area of the photo which is in focus. The distance between the closest object and the farthest object which are in acceptable focus is called the depth of field.

You can control depth of field by adjusting settings on the lens and the distance to the subject. Often times we want as much of the picture as possible, but sometimes we want to narrow the depth of field to emphasize the subject. We call this “selective focus”.

Depth of field is determined by four factors:

1. The focal length of the lens. The longer the focal length, the narrower the depth of field.
2. The aperture of the lens. The larger the aperture, the narrower the depth of field.
3. The distance to the subject. The closer the subject, the narrower the depth of field.
4. The size of the sensor/film used. The larger the sensor, the narrower the depth of field can be. Full-frame cameras are better at selective focus than crop sensor cameras (APS-C, Micro Four Thirds).

Most photographers know about using selective focus to defocus backgrounds in order to make the subject pop. It’s a standard trick, even cliche in portrait photography. The 85mm f/1.4 lens is a portrait photography classic because it excels at this

However, you can use the same technique of using a telephoto lens with a wide-open aperture to make unwanted foreground elements disappear.

Making foreground elements “disappear”

To make a foreground element, such as the chain link fence in the examples below, disappear, we choose a focal length and aperture combination with a narrow depth of field. For the picture on the right, I used my Tamron 70-180mm f/2.8 lens zoomed in to 180mm and the aperture set at f/2.8. I focused on the snow leopard’s eyes, and the depth of field is so narrow that the fence is so completely out of focus that it “disappears”. The other photo was shot with the aperture stopped down to f/11, giving a much wider depth of field.

Click images to enlarge.

Using high ISO settings like a night vision device

Camera ISO number is a setting that adjusts the camera sensor’s sensitivity. Lower ISO numbers are less sensitive to light. Higher ISO numbers are more sensitive to light. Lower ISO numbers generally provide better image quality. The term “ISO number” originated as a measure of sensitivity of photographic film. Camera ISO numbers correspond with film ISO numbers.

Mirrorless digital cameras can shoot stills and video at ISO settings in excess of 100,000. This can give you usable images in low-light conditions where you can barely see anything with the unaided eye.

In this video I demonstrate this by shooting clips of bats at the zoo at “normal” indoor ISO settings, such as 400 and 800, and then I bump the ISO up to 32,000 for some cool slow-motion footage.