Field Curvature

How to analyze and work with this ubiquitous lens problem
written by: Lloyd Chambers

Field curvature can make a sharp lens look soft when the wrong assumptions are made. Understanding how sharpness varies throughout the frame will help you get the most out of some excellent lenses that might not test well on flat (planar) test targets. In previous articles, I’ve explored how diffraction and focus shift can lead to images with degraded contrast and resolution. As if that wasn’t enough to think about, another confounding factor is present: field curvature. In the ideal world, a flat (planar) surface would be imaged onto a flat sensor, and a crisp image would result (a “flat field” Read more »

(Figure 1) 105mm vs. 24mm

Understanding Lenses

written by: Alan Ross

There are two primary elements of choosing and using a lens: what focal length to use and where to focus/what aperture to use. Let’s take a look at how these elements affect an image. How Does Focal Length Affect Your Image? The only thing that changes when you use a different focal length lens is the cropping of your image! Optical aberrations aside, short focal length or wide angle lenses do not distort close subjects, and long focal length or telephoto lenses do not compress subject features. What really causes these familiar effects discussed so often in popular texts is Read more »

Purissima Creek after Spring Rains. Nikon D3x + Zeiss 15/2.8 Distagon 1/10 sec @ f/11

Carl Zeiss ZF.2 / ZE 15mm f/2.8 Distagon

written by: Lloyd Chambers

The new Carl Zeiss ZF.2 / ZE 15mm f/2.8 Distagon for Nikon or Canon offers unprecedented optical performance in an ultra wide angle lens, with superb build quality and ergonomics. Introduction As digital camera sensor resolution increases, the demands on lens performance rise, with many lenses inadequate to the task of ultra high resolution DSLRs like the 36-megapixel Nikon D800. The exciting and newly developed optical formula of the Zeiss 15mm f/2.8 Distagon for Canon or Nikon DSLRs is an answer to those demands in the ultra-wide realm. The Zeiss 15/2.8 Distagon offers an unprecedented level of performance that makes Read more »