Focal length 35mm equivalent, but not F-stop?

Started Jul 24, 2014 | Discussions thread
eyeswideshut Regular Member • Posts: 333
Re: Focal length 35mm equivalent, but not F-stop?

Lee Jay wrote:

John Sheehy wrote:

Chikoo wrote:

All camera manufacturer when they publish technical specification of their camera lens publish the focal length and it's equivalent in 35mm. But the same is not done for F-stop. Why?

f-numbers are ratios of real focal length divided by physical aperture size, and have nothing to do sensor sizes.

If manufacturers used the "35mm equivalent focal lengths" in the ratio, then they'd also have to scale the ISOs also to make exposure triangles work. Do you want that kind of a mess?

Absolutely I do.

Lee, no one is stopping you from engaging in all those calculations. Get down and dirty with the math!

For the great unwashed though, focal length is what it has always been: shorthand for angle of view. It's been that way for ever and ever and ever. And that is all that manufacturers are implying when they give equivalent focal lengths. Only when you ignore that simple semantic fact can you meaningfully go off on the equivalist tangent.

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