Quote:
Originally Posted by marknorton
To a first approximation, lenses follow the basic formula:
1/f = 1/u + 1/v
At infinity, the lens is exactly "f" in front of the focal plane, 50mm. At 200metres, it moves slightly further forwards to 50.0125mm, or by 1/80mm. To a first approximation then, your lens is sitting 1/80mm too far forwards.
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Mark:
1. Can you explain the basic formula? What is "u", "v"
2. How can you find 200 m and 0.0125 mm?
Thank you in advance.
Michel