Just how good is the 20/1.7?

Started Nov 9, 2012 | Questions thread
John Bean (UK) Forum Pro • Posts: 18,035
Re: Just how good is the 20/1.7?

Mingjai wrote:

I suspect the 20mm is slightly wider than its nominal focal length because it's very close to my 9-18mm at 18mm.

I see a significant difference in your examples, certainly enough to accommodate the 2mm difference.

I think perhaps some of the "wider than it says" claims come from measurements from a raw conversion without the design-specific software corrections, where its FoV is closer to that of a 18mm lens albeit with lots of barrel distortion.

But used correctly with software corrections applied - as the designers intended - it's pretty much exactly 20mm.

PS: I don't currently own this lens but I owned and used it in its early years when heated controversy surrounded this exact point. I confirmed the matter of "real" FL myself, believing nothing I read on the internet as "fact" without evidence.

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