Sharp or Just Acceptably Sharp?

Today’s Post by Joe Farace

For my digital image processing, I use 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 on today’s 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 that the area in front of and behind the focus plane still appear more or less in focus or at least acceptably sharp. That’s what depth-of-field is all about.

Depth-of-field is the 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 measurably one-third in front of that point and two-thirds behind it.

Hyperfocal Distance is the specific point of focus where an object between that distance and infinity is in focus. While aperture rings have more or less disappeared from lenses, some lenses still have them, such as Voigtlander’s Nokton 10.5mm f/0.95 lens. Most vintage lenses have a depth-of-field scale, which can be helpful when using hyperfocal focusing, which I do when shooting with 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. At that point, your camera can operate as point and shoot, which is how I use manual focusing lenses when shooting infrared.

Special offer for this blog’s readers that’s good for the next 30 day: If you want to save $50 off at LifePixel for Priority Processing Upgrade when converting your camera to infrared, use the coupon code “MarkToalIR.”

IR.bookMy book, “The Complete Guide to Digital Infrared Photography,is out-of-print but used copies are available from Amazon for less than three bucks. Creative Digital Monochrome Effects has a chapter on IR photography and new copies are available for $5 from Amazon with used copies essentially free—one cent plus shipping.