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3 Cards in this Set
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Define Accurate transposition |
The power of a lens is not simply the sum of its surface powers (F=F1 + F2) in real lenses (especially plus powers) thickness cannot be ignored. |
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Define Effectivety |
When a spec lens is moved from its original vertex distance to a new position, the power required for correction will change. The new power is the 'effective power. d = the change. |
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What is the effectively formula? |
Feff = F/1-dF (closer to eye)
Feff = F/1+dF (further from eye). |
