Idaho Airships, Inc.

…courtesy of the Office of Naval Research, no less. See the pdf.

This is an excellent place to start an exploration of human visual acuity. The article doesn’t just deal with the physiological aspects of sight-it explores the energy (specifically, visible band light) that we as imagers are collecting and manipulating.

It is very important when reading generalizations such as the term “human vision” that you understand human vision is actually wildly variable, and that it is crucial to incorporate statistical qualifiers in critical applications of the standard. This article doesn’t deal with binocular vision, field of view, ocular pathologies, or our hemispherical retinae, but those things will wait.

One of the most interesting and important issues reviewed in this publication is on page 190-the chart illustrating mixed lighting of varied Planckian Loci. The 2D chart shown, unfortunately, uses two loci that are unrealistic to demonstrate the averaging effect. While it would be much more effective to represent the loci on on accurate Blackbody curve (see Figure 11.8) within a 3 dimensional Gamut, I can sympathize with the lack of necessary time to construct such an artifact and the bandwidth challenges in distributing it.

The graphic on page 190 also does not take into consideration more than 2 differentiated light sources (which is an extremely common existing-light shoot condition) or varied luminance levels by those sources. You’ll simply have to extrapolate on those matters for yourself.

Another extremely interesting matter is the Color Rendering Index discussion on pages 92-93, and the accompanying chart (Table 11.5) identifying the CRI of sodium (Na) vapor lights as extraordinarily low.