A calibrated gray scale for forensic ultraviolet photography.

The human eye is an important tool for observing evidence, and visual evidence in turn may be documented onto a photographic medium. The human eye is generally sensitive only to a narrow band of the electromagnetic spectrum from about 700 nm (red) to about 400 nm (violet/blue). It is possible to extend the range of radiations over which evidence may be documented by using the natural ultraviolet sensitivity of photographic films.

Aquatic vision and the modulation transfer properties of unlighted and diffusely lighted natural waters.

The modulation transfer function (MTF) of well-mixed unlighted and diffusely lighted samples of clear natural waters for path lengths up to 4 m was measured. The measuring conditions simulated the situation for horizontal aquatic vision. In unlighted water, the MTF decreased relatively slowly with increasing path length and spatial frequency up to 150 c/deg.

Microspectrophotometric determinations of rod visual pigments in some adult and larval Australian amphibians.

Visual pigments from the red rods of adults of eight species of Australian anuran amphibians, from a variety of habitats, were analyzed by microspectrophotometry. The lambda max in all cases fell between 502 nm and 506 nm, and the absorption spectra were well fitted by an A1-based visual pigment template curve. Red rod pigments were also analyzed for a number of tadpoles.

Annual variations in the visual pigments of brown trout inhibiting lochs providing different light environments.

Visual pigments were extracted at regular intervals over the year from trout (Salmo trutta) inhabiting three Scottish lochs. Measurements of the spectral quality of the light in the lochs were also made. In all cases only A2-based pigment was found in the winter, with A1-based pigment appearing as well in summer.

Visual adaptations to different light environments in Amazonian fishes.

Light measurements were made at seven sites in the Amazon river system near Manaus. It was found that very little light penetrates into the white water of the Solimões because of the large amount of suspended material it contains. In lakes off the Solimões the suspended material settles out, and light penetration is increased.