Actinometers

Wynne’s Infallible Hunter Meter c1915

Toronto. Since the beginning of photography people tried to find reliable ways to predict the correct exposures for a given light and scene. One idea was to expose a sensitized contact paper in the shadows enough to “tint” the paper slightly and then calculate the needed exposure based on how long it took for the paper to tint.

In 1893, Wynne of Wrexham, Wales patented the “Wynne’s Infallible Exposure Meter“.  A few years later, the meter was simplified as the “Infallible Hunter Meter” which was built into a slim pocket watch-like case. On one inner side was a round hole to expose the sensitive paper edged on two sides by tints too light and too dark. A milled ring allowed the hole to be rotated to a fresh spot on the paper. The ring could be aligned with the case hinge and “winder” allowing the ring and its plate to be carefully pulled up to insert a fresh piece of paper. Snapping the case closed protected the paper from light, eliminating the previous need for an orange filter.

When the time taken to darken the paper midway between the two tints was transferred to the scale on the other side of the inner watch case, the photographer could determine the most suitable aperture and shutter speed to use. There was a special accessory disk for the colour materials of the day.

My meter was dated 1915 and came with some sensitive papers and a protective leather pouch all in a small tin box. Also in the little box was an instruction booklet and an August 1922 list of current plate speeds from Pat’s Camera & Sports at 747 Broadview Ave (Toronto). 747 is near Danforth (Bloor continuation east) and was a restaurant a decade or two ago when I went to see my dermatologist at 741.

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