Warnerke Standard - Antique and Vintage Cameras

Warnerke Standard

1880

Marion & Co. Ltd

London

England

Image of Warnerke Standard

Consists of a printing frame, density plate with 25 squares of varying density, phosphorescent tablet and holders for magnesium ribbon. Quarter-plate size.

Notes:
Address on box: Marion & Co. 22 & 23 Soho Square.

With:
Box with Marion label.

This is the earliest commercial sensitometer preceding the work of Hurter and Driffield. The standard light source is a phosphorescent tablet that has been exposed to burning magnesium ribbon. The plate to be measured is placed behind the graduated density plate in the printing frame and exposed for a fixed time to the phosphorescent tablet. The rapidity of the plate can be gauged by seeing which of the graduated squares is visible. This instrument was widely used and several manufacturers labelled their plates with Warnerke numbers. The value measured was the threshold value of the plate. Each Warnerke number represented a 1/3 increase in speed over the previous. The price was 15/-.

Having found a value for the speed of the plate, the Warnerke value, the photographer had to calibrate this in terms of exposure (aperture and time). After finding the Warnerke value of a plate another plate from the same batch was exposed in a camera to find the exposure required by that particular Warnerke value. A calculator could then show the relative exposure for plates with other Warnerke values.

References & Notes:
Marion's Guide to Photography, p. 261. Eder, History, p. 450. Abney, Instruction, p. 141.

Warnerke Standard

1880

Marion & Co. Ltd

London

England

Similar to the entry above but the standard density plate is missing. The calculator with this example allows the relative exposure for plates with different Warnerke values to be determined once an initial Warnerke value has been found and calibrated against an aperture and exposure time.

Notes:
Address on box: Marion & Co. 22 & 23 Soho Square.

With:
Instructions. Box with Marion label.


Company Details:

Marion

Sensitometry

Warnerke Standard

Sanger-Shepherd

Dawson's Densitometer

Graduated Annulus

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Ilford Colour Chart


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