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Since the positive was mounted at the same distance from the magnifier’s optical system as the ground glass, both were brought into focus by the same adjustment of the camera’s focusing system.
The flashlight globe behind the positive was supplied by a battery mounted in a small case on the tripod. On this case there was also a rheostat and a milliammeter. Thus it was easy to standardize the illumination of the positive; all that was necessary was to manipulate the rheostat to give a standard reading on the milliammeter, and one could be sure the illumination on the positive would he at the desired standard.
Practical Operation
In actual use, all that was necessary was to turn on the light to the desired standard strength, and flip the lever that brought the reflecting mirror into place. Then I would simply close down the diaphragm of the camera’s lens until the illumination of the image seen on the ground glass matched that of the standard positive. That would be the correct exposure!
When using filters, I could simply put the desired filter in place before the aperture by means of the Mitchell’s revolving filter disc. Then, holding an identical filter before my eye, I would adjust the diaphragm again
in the same way, to match the two images.
Crude as it now seems, this meter worked with surprising accuracy. I still remember how my first test of the device surprised me. After having gone to some little trouble to make the device, I felt it ought to work, but I must admit that I had none too much confidence in it. Especially after setting the thing up and making a strictly visual test!
I had chosen a spot in the bright sunlight beside one of the stages at the United Artists Studio; my own judgement of the correct exposure for that shot was, as I remember it, about /: 8. But when I had matched the densities in my meter, I found I had my lens set at about / : 1 8. That couldn’t be right!
I was about to pack things up in disgust when my Assistant, who had sweated mightily over getting the thing together and adjusted on my camera, urged that there couldn't be much to lose if we exposed a few feet of tests — and it would be a pity to go to so much trouble with nothing to show for it! So we compromised by shooting some tests of a variety of light-conditions: “hot” front-lights, top-lights, cross-lights, back-lights and even in deep shadows. So assured was I that the readings my meter gave were impossibly wrong that I slated the roll “Do Not Print!”
Sortie of the tests described by the author. The pictures reproduced above are enlargements from 35 mm. negative exposed in 1928. All received identical printing.
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