The is a sturdy, paper-based guide to exposing film correctly. The guide was published on 30 November 1945 and purchased by an unknown photographer on 29 July 1946. At this time, calculating exposure was made difficult as there was no standard way of measuring film speed. This guide makes no mention of either ASA or DIN, which we have come to think of as usual – and was well before ISO him speeds. The guide has several pages of “exposure factors” for each type of film likely to be found in 1945. Ilford films, as an example, were advertised with “speed groups” which were only used by Ilford as well as H&D and Scheiner speeds. Barnet films were given an H&D speed rating, Kodak films had º Kodak. Weston meters used Weston speeds which were not used by any film makers. It must have been a nightmare – even Sunny 16 would be difficult without ASA speeds!
Enter the Welcome Photographic Exposure Guide. This has twenty pages of information, four pages of example photographs and a handy exposure dial. This guide is rather complicated – very much so for those of us used to modern automatic exposure cameras.
First, you need to ascertain the current light value. There are tables to enable you to do this – one table for each month which is divided by time of day vertically and weather horizontally. So, I am typing this on 4th May on a cloudy day at 5.00 pm. The May table gives me row four (7 a.m. and 5 p.m.) and column three (Sun obscured by light cloud or slight mist). The light factor for this is 1 with a note that this number must be used with caution and might need to be increased by five or ten times.
Second, I need the exposure factor for the film I am using. If I am using Ilford FP2 (it is likely to be FP4+ in real life) I need to go to the list of films and plates starting on page ten and find my film – page 13, miniature films (=35mm) – where I find that my film has an exposure factor of 1/24 or 1/32. 1/24 is the shortest exposure that will give a fully-graded negative and 1/32 is the shortest exposure that will have any hope of success. I want a good negative so I go with 1/24.
Third, I need to decide if my subject is ‘normal’ or not. If not normal, there are several options: Distant landscape, open beach, snow perhaps or Heavy foreground or maybe Portraits, groups. Well, I like landscapes and so will go with that.
Fourth, I need to know what aperture I am going to use. It will be ƒ/5.6, usually so I will go with that.
To use the dial on the inside of the back cover, I line the green 1/24 against the black 1. Next, I look at where the black pointer is pointing (1/4 in this case) and move the word ‘landscape etc’ against the 1/4. At the other end of the dial, I find ƒ/5.6 and read the red shutter speed off – 1/200 seconds.
If I wanted to decide the shutter speed rather than the aperture, I could decide to use 1/500 seconds, look at this in the red figures and read the aperture off – between ƒ/3.5 and ƒ/4
Actually, this is not so hard to do. If you habitually use the same film you would soon memorise the Exposure factor – 1/24 in my example as this will not change for the entire film and probably not for most films. Again, you will only need to check the light value every hour or so. Indeed, once you have got your exposure settings, you need change nothing for the entire sessions in most cases. At the time, this was probably useful for serious photographers but I much prefer my Zeiss Ikon Ikophot hand-held meter.
To help you decide on the classification of your subject, there are eight reference photographs to compare with your subject. These photographs, together with the other pages of the guide can be found below.