Watkins' first exposure meter, the Standard, proved popular despite its cost. It remained on sale until the mid 1920s though it was largely replaced by the Bee (1902).

The meter uses a strip of sensitive paper, a small section is exposed to light until it reaches the density of a comparison tint. This gives the actinic value which is set on a calculator scale and combined with values for plate speed, diaphragm and subject. The result is the required exposure time.

Early models have 5 scales and a blank ring, they are (in order back to front): A P S D E with a blank ring between the D and E scales. Later models have the dials in different orders. In 1895 the Subject pointer was removed, the subject scale was located on the final ring opposite the exposure. Early models have the name, on the end of the meter, in simple lettering, later a flowing script is used.

Before 1900 the manufacturer was R. Field & Co. From 1900 it was made and sold by the Watkins Meter Co. which took over the 'goodwill, stock and book debts' of the exposure meter side of R. Field. The cost in 1890 was 15/- later this was increased to 21/- and from the mid 1920s the price was 30/-. A model in magnalium rather than brass was also produced, probably until around 1917.

Watkins Calculation

• A is the actinic value in seconds and is the time taken for the sensitive paper to darken to a standard tint.
• D is the diaphragm measured on a Watkins scale, where f4 = ¼, f5.6 = ½, f8 = 1 and so on.
• P is the plate speed measured in Watkins units.

A subject scale, S, is sometimes present, the neutral value is S100 other values such as S25 (snow or sea scenes) reduce the exposure by ¼, S50 (open landscape) reduces the exposure by ½ and S150 increases the exposure by ½.

An F scale is present on Enlarging models, this takes into consideration the effect of bellows extension when copying in the camera and enlarging from a negative onto paper. For copying where the image is smaller than the original, the F scale shows the distance of the subject from the lens in focal lengths i.e. distance/focal length. For enlarging (greater than same size) the scale shows the distance of the printing paper from the lens in focal lengths.

The scales on the Standard are cluttered making them difficult to read. The calculation is, though, straightforward. In the first entry above the aperture values are equally spaced around one of the rings, the E, S and A values double for each smaller stop, the P value doubles for each larger stop.

As with other actinometers the reading is taken from the position of the subject. A pendulum is attached to the meter and measures in seconds.

This is a simplified version of the Watkins Standard. The subject scale of the Standard is replaced by a table on the base of the meter. There is no cap or pendulum. The price was 7/6. The Junior was withdrawn probably around 1902 when the Bee was introduced.

In use the P index is set to the plate speed and the D index is set to an aperture. The actinic time then points to the exposure time.