More in Focus

December 26, 2016  •  Leave a Comment

A few years ago I visited a national cemetery. In an effort to compress the many tombstones, I attached a telephoto lens to my camera and created several compositions. I knew that it would be challenging to get enough of the tombstones in focus in a single image with such a long lens. But, until I actually experienced the photo shoot, I had little appreciation for how challenging this actually is!

The reason it is so challenging to get enough of the tombstones in focus is that the depth of field is relatively narrow, even at the narrower apertures, when using a lens with a longer focal length. Let's take a look at the 300mm 2.8 lens for a moment:

  • If one focuses a 300mm lens at a distance of 100 feet, the depth of field for acceptable sharpness ranges from 86 to 119 feet when using an aperture of f/16. Even with this relatively narrow aperture, only the tombstones that fall with those 32 feet will be in focus. Any tombstones closer than 86 feet or further than 119 feet will look blurred.
  • I usually avoid selecting an aperture as narrow as f/16. Lenses aren't as sharp at that aperture. A wider aperture, such as f/8, will generally produce a higher quality image. But at f/8, the depth of field for acceptable sharpness is narrower--from 93 to 109 feet, or just 16 feet!

The lesson here is that even when a very narrow aperture is selected, it's impossible to get all of the tombstones in a large portion of the cemetery in focus.

Last month, I visited the Chattanooga National Cemetery. This time, I used a different approach. For the photograph shown below, I used my Nikon 300mm lens and set the aperture at f/11. I took three exposures of the scene. I focused on a tombstone in the front of the frame for the first image, a tombstone in the middle of the frame for the second image and a tombstone in the back of the frame for the third image. During post processing, I blended the three images so that the tombstones throughout the entire frame are sharp! To accomplish this, I secured my camera to a tripod to minimize the chance of introducing camera movement between exposures.

Here's the final image:

Chattanooga National CemeteryChattanooga National CemeteryChattanooga National Cemetery at 1200 Bailey Avenue in Chattanooga, Tennessee on November 10, 2016

Of course, not all images must be sharp from front to back. Sometimes it's desirable to focus on one section of the image while letting the rest of the picture fall out of focus. I used this approach for this next shot--which required just one exposure:

Chattanooga National CemeteryChattanooga National CemeteryChattanooga National Cemetery at 1200 Bailey Avenue in Chattanooga, Tennessee on November 10, 2016

The more I shoot, the more I find value in capturing multiple exposures and then blending them during post processing to solve a number of challenges.


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