Today’s Post by Joe Farace
When I updated my old computer to a 5K iMac it changed the way that I view and work with many of my older images. Photographs that were made with older, lower resolution digital cameras and viewed on older, softer CRT monitors don’t compare with how they look today on higher resolution, crisp and contrasty LCD monitors.
It’s also changed my workflow: When looking at photographs on the 5K monitor I confronted two different situations: How bad some of them looked and not just because of resolution but what appeared acceptably sharp on a 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 appear more or less in focus or in 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, decreases as the aperture gets larger and the camera to subject distance decreases. At 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.
How I Made this Shot: I photographed this hot rod using a Lumix G5 that had been converted to infrared capture by Life Pixel. Lens was the Lumix G Vario 12-32mm f/3.5-5.6 kit lens (at 12mm) that is bundled with many Panasonic cameras. Exposure was 1/50 sec at f/11 and ISO 400. The RAW file was opened in Adobe Camera RAW (at right) then converted to monochrome using Silver Efex Pro.
Tip: Which is why, especially when shooting infrared, I use Hyperfocal focusing with manual focus lenses. 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 but this is a gradually disappearing feature. Most vintage lenses have a depth-of-field scale, which can be helpful when using hyperfocal focusing. Here’s how it works: You 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. Bingo, you’re all set and it’s how all of my images made with the Zenitar manual focus lens were made.
For another take on the concept of sharpness, please take a look at my post “The Sharpest Knife in the Imaging Drawer,” when you have time.