Is That Photograph Sharp or Just Acceptably Sharp?

“If the point is sharp, and the arrow is swift, it can pierce through the dust no matter how thick.”—Bob Dylan

Regular readers know that I updated my old computer to a 5K iMac and it’s changed the way I view and work with older images. Images made with older, lower resolution digital cameras and viewed on older, softer CRT monitors don’t compare with how they looked today on higher resolution, crisp and contrasty LCD monitors.

It’s changed my workflow: When looking at photographs on the 5K monitor I confronted two different situations: How bad some of them look and not just because of resolution but maybe what appeared acceptably sharp on an older CRT monitor looks unacceptably soft at 5K. On the other hand, some of my sharper images literally leaped off the screen.

The basic laws of imaging state that only one part of a three-dimensional object can be in focus at the image plane. This means areas in front of and behind the focus plane still appear more or less in focus or acceptable focus. That’s what depth-of-field is all about.

Depth-of-field is an area that your eyes perceive as being in focus and is affected by several things. Depth of field increases as the lens aperture is stopped down and decreases as the lens aperture gets larger and the camera to subject distance decreases. 10.5mmAt the point of critical focus, there is a range of acceptable focus that is one-third in front of that point and two-thirds behind it.

The Hyperfocal Distance is the specific point of focus where any object between that distance and infinity is in focus. Some lenses have an aperture ring. Most vintage lenses have a depth-of-field scale, which can be helpful when using hyperfocal focusing, which I do when using manual focusing lenses. Here’s how it works: Select an aperture on the lens, then rotate the focusing ring setting so that aperture appears opposite the infinity mark on the lens’ depth-of-field scale. And “Bob’s Your Uncle.”

Look for my review of Voigtlander’s Nokton 10.5mm f/0.95 lens in an post on our sister blog, Mirrorless Photo Tips.

Author: Joe Farace

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