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marknorton · 01/12/07, 12:10 AM

The folks in the German forum are correct. These figures reflect the fact that manufacturing tolerances can affect the focal length of the completed lens. The 19 in this case does indeed mean the measured focal length is 51.9mm.

Other lenses have it as well. My pre-ASPH 50/1.4 has "13" and even my 50/1.4 ASPH has "14", so it's not just older lenses which have it.

Keep in mind that the effective focal length changes a little as the subject distance changes.

01/12/07, 12:10 AM	#2 (permalink)
marknorton Erfahrener Benutzer Join Date: 11/12/02 Posts: 5,269	Re: Strange number on my Elmar The folks in the German forum are correct. These figures reflect the fact that manufacturing tolerances can affect the focal length of the completed lens. The 19 in this case does indeed mean the measured focal length is 51.9mm. Other lenses have it as well. My pre-ASPH 50/1.4 has "13" and even my 50/1.4 ASPH has "14", so it's not just older lenses which have it. Keep in mind that the effective focal length changes a little as the subject distance changes. __________________ Mark