On Jan 15, 2009, at 8:38 AM, Peter Alling wrote:
As the "normal" lens focal lenght is the diagnal of the film, (now sensor),
That's a technical definition. "Normal" is not only defined by a technical definition, it's also by convention in use.
50mm was considered the normal for 35mm cameras for many many years, just as 75mm was considered the normal for 645 and 6x6. The latter is a wider FoV than the former ... and the reason for the difference in convention is twofold:
a) 35mm was considered a miniature format, and a slightly longer normal convention was felt important for image quality given the limited amount of film area.
b) 35mm SLR cameras with a 42-46mm mount register made it much easier to design and build 50mm lenses than 35mm lenses, so the convention shifted from the 35-40mm range to the 50-58mm range.
There's no such thing as a "true normal". There's only what exists by convention.
BTW, Panasonic will be releasing a 20m f/1.7 lens for the G1 soon ... a "true normal" by your definition that (by the look of the preview photos) is half the size of the Pentax 21mm f/3.2 Limited.
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