http://www.nikonchat.com/75mm-nikkor/
I multiply the nikkor 18-105mm on a 1.5 factor of half frame digital SLR [D90]?
I know I should do with the 50 mm so be more like 75mm. and 75mm isn't really more in the telephoto range and would not be so practical for regular use?
Yes, it is used the crop factor of 1.5, so the 18-105 should be given the 35-mm field of view equivalent to 27-157.5mm lens. Focal length is the focal length has nothing to do with the sensor or film. We use the equivalent to 35 mm for your convenience, so everyone is playing in the same field.
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