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

Started Jul 24, 2014 | Discussions thread
Lee Jay Forum Pro • Posts: 55,138
Re: Focal length 35mm equivalent, but not F-stop?

AlbertInFrance wrote:

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.

While you're at it shouldn't you make publishing MTF curves compulsory? They are quite useful for comparing lenses and you can't just calculate them on the back of a fag packet.

Not publishing them isn't the same level of dishonesty as publishing equivalent focal lengths combined with actual f-stops.  It's an omission only, not a deception.

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