Rethinking focal length conventions

Started 9 months ago | Discussions thread
Phil A Martin
Phil A Martin Veteran Member • Posts: 6,767
Re: 6%

Gerry Winterbourne wrote:

Phil A Martin wrote:

jrtrent wrote:

tko wrote:

You're thinking you need a 40 mm instead of 35 mm? Of what importance is this? How did you get this conclusion? How would a 85/80 = 6% difference in FL rock your world? I don't get this at all. It would seem like you think your numbers are better since they are "more rounded off," and you want lens manufacturers to come up with new products where the focal lengths are "prettier."

You may be right about the difference between 80 and 85 mm, but apparently there's a noticeable difference around 40mm:

"40mm is the "Perfect Normal" focal length for full-frame. Unlike 50mm lenses which often are too long or 35mm lenses which are often too wide, 40mm is always just right."

And that's from Ken Rockwell himself!

He's wrong, it's 43mm is actually the perfect focal length for full frame. It corresponds to the sensor diagonal of 43.27mm.

There is no single "perfect" focal length. Human eyes vary in size; if "perfection" means matching human vision then it varies depending on the individual. 43mm was picked out of the range of visually "normal" focal lengths because it corresponds to the diagonal of 135 format - an arbitrary choice that doesn't confer perfection.

It is the focal length of the "true" standard lens, where perspective is seen as the human eye sees it. This has been an acknowledged truth throughout the history of photography and is easily demonstrated in practice.

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I'm happy for anyone to edit any of my photos and display the results
First camera 1953, first Pentax 1985, first DSLR 2006

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