Wednesday 8 May 2013

Old Advice on Exposure Compensation - No Wonder We Were Confused


We all now know that exposure meters for reflected light give a misleading reading for snow scenes and that we have to give about two stops more than is indicated by the meter. This is because meters are calibrated for a mid-grey balance between shadows and highlights. The meter interprets the very bright light coming from snow as mid-grey and therefore suggests a lower exposure than in necessary for the nearly all white content. The converse applies to scenes in which dark shadow predominates.

I knew at some time in the past I had read the opposite — and completely wrong — interpretation. Then while researching an article on Alex Pearlman for Club Rollei User Magazine, I came across the following in his Rollei Manual (5th edition, 1971):

Almost all such meters in use today, including those fitted to the Rolleiflex, are known as ‘integrating meters’, that is, in manufacture and calibration, an equal amount of high-light and shadow area is catered for, as this holds good for the vast majority of scenes...From this it will be seen that if the light reflected by a certain subject is all of a light tone, and there are practically no dark areas of tone or of shadow, then approximately fifty per cent less exposure should be given than that indicated by the meter, as this is still thinking for us in terms of equal quantities of high-light and shadow area. Similarly, if a dark subject is being photographed, in which there are very few light accents — and shadow predominates, it will be necessary to give approximately fifty per cent more exposure than that which is indicated by the meter, for exactly the same reason.

Oh dear. I wonder how many people followed his advice and got even worse exposures in snow or deep shadow. But the older readers of this blog will remember that Pearlman was well know for his snow scenes, some of which appear in the Rollei Manual. Well, by chance, I came across an article of his in Amateur Photographer of 1 December 1954 entitled To the Mountains in Winter. What did he have to say about exposure? He was successful in achieving the correct exposure as the photographs illustrating the article demonstrate. This is what he wrote:

Technicalities should present no problems, as there is always more than adequate illumination. The exposure meter should be left at home! Even incident light meters rarely give the correct reading and all types indicate too short an exposure under snow conditions.

So, he was right about the direction of error in 1954 (even if he did not know its magnitude) but not in the Rollei Manual. Very strange.

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