Mischa,
When you go from an SLR film camera to a digital, such as the Nikon D70, you must do a conversion regarding focal length. For example: if Sharon were to take her 55mm or 85mm lenses and use them on the D70 she would then have to do a conversion using a 1.5 multiplier.
These multipliers will be slightly different between manufacturers. I think the Canon is 1.6 times the old focal length.
So, the 55 becomes 82.5 and the 85 becomes 127.5. I try not to get to deep into the reasons for the conversion, maybe I knew at one time but have gladly forgotten.
It's also important to know that after you make the conversion, the old benchmarks will remain the same. For example: if 80mm was the optimum focal length (many fixed length portrait lenses are somewhere close to 80mm for all the reasons Sharon mentioned) then it will still be 80mm after the conversion. This is my understanding, if someone can correct me here please do.
Most distortion comes when you descend below 50mm.
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Mike McCarty
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