Weston Master IV Exposure Meter, Model 745. 1960 UK manufacture only.
The Master IV does not use the term 'Universal' on the meter face. The dial legend also dispenses with intermediate markings for aperture (f stops) and shutter speeds. The meter needle lock makes it possible to use the meter for incident light readings with the Invercone, when the face is turned away from the user.
This is also the only model in the Master family to dispense with thumbnail vanes at the ends of the calculator dial section, having instead a knurled outer rim that rides proud of the meter body, allowing adjustment of the dial with ease. (the vane feature was restored in the Master V and subsequent models).
The use of an American designation model number and a black background meter face may have been informed by the large export sales from Britain back to the USA.
The Weston Master IV and subsequent models used a redesigned and efficient Invercone for incident light measurements. This was made out of fragile perspex and had a tendency to flick off the meter if the baffle were released from its body lock while the Invercone was mounted. Many fractured and broke as a result.
A variant of the Master IV also appeared with a redesigned calculator dial. It had a red pointer and the 1/3rd stops were also restored on the aperture and shutter speed scales. Judging from appearances on auction sites, about 10% of those in the USA and Canada may have been of this type. None seem to have been sold in Britain.
Not every Weston Master IV was made by Sangamo in England. With Sekonic making a virtualy identical model under their own name, the L104, under license from Daystrom in the USA, some were badged up directly as 'Westons' for American distribution. The Sekonic Weston is shown for comparison on the right.
At first glance it appears identical. But close scrutiny reveals some minor differences: Rather than pure white divisions on the meter face, they are coloured in a light flesh tone. The steps are also spread differently across the scale, with the lower ones on the left spread further, and the top end to the right, crushed. This may be to reflect a different calibration of the photoelectric cell in Sekonic's manufacturing process.
On the backs of the Sangamo and Sekonic Weston IVs, their respective origins become clear, though for the Japanese meter, 'Sekonic' is not mentioned. The designation S461-4 is used by Sangamo, whilst for the USA, it is 745. Another design difference is apparent here in the size, number and distribution of the perforations in the range baffle.