As was mentioned above, modified red-ringed Nikon loupes were being sold by Rubin & Son in the early 1970''s. Similar loupes may have been used in Russia in the 1960''s, though I haven''t been able to definitely confirm this. It would be interesting to know exactly where these techniques originated.Date: 1/5/2005
Author: Fleimstaler
On the 28th April 1980 Mr. Okuda wrote me a letter telling me about the loupe with the red ring, and attached a sample to it. He suggested to use Nikon or Zeiss loupe that was easly available on the market. The reason for choosing these loupes was that both had 50 l/mm resolution.
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I first met Mr. Okuda in 1978 and therefore I can confirm that his method of green light reflection for cut grading dates back to that time.
one of the main features of the green light is to align the table, the table should be completely green which means that the table is square to the light.Date: 8/17/2004 12:00:10 AM
Author: Superidealist
On page five of the manual, it says that the green light is to be turned on during proportion grading.