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JJJPhoto · 08-07-2008, 09:45 AM

Originally Posted by VAV

I am curious about how Pentax came up with the focal lengths for the three FA limited lens - 31, 43 and 77 - How do they decide on these focal lengths ?- why not, for example, 30-50-75?

Thanks

I'm not sure about the 31mm and the 77mm, but 43mm is the "true normal" perspective for 35mm film. That's because 43mm is exactly the diagonal length of 35mm film. With the 1.5x crop factor of APS-C sensors that probably makes a 28mm the "true normal" for our DSLRs.

08-07-2008, 09:45 AM	#2
JJJPhoto Senior Member Join Date: Nov 2006 Location: Cincinnati, OH Gallery Photos: 0 Posts: 245	Originally Posted by VAV I am curious about how Pentax came up with the focal lengths for the three FA limited lens - 31, 43 and 77 - How do they decide on these focal lengths ?- why not, for example, 30-50-75? Thanks I'm not sure about the 31mm and the 77mm, but 43mm is the "true normal" perspective for 35mm film. That's because 43mm is exactly the diagonal length of 35mm film. With the 1.5x crop factor of APS-C sensors that probably makes a 28mm the "true normal" for our DSLRs. __________________ www.jjjphotography.com http://jjjphotography.blogspot.com