M43 or MFT is my preference for the Panasonic and Olympus Micro Four Thirds cameras. Panasonic often used/uses “CSC” for “compact system camera”. I thought that was pretty forward thinking.

Well, this whole f-stop thing was determined in the days of prime lenses, and in those days, on most lenses, we had a depth of field indication, which also contributed to a speedy discovery of the hyper-focal distance for any f-stop. But most people these days use zoom lenses, so the effective f-stop is altered with the extension or compression of the lens. So for a zoom lens the light transmission changes independently of the aperture, which creates almost as many problems as the inaccurately termed “inverse square law of light”. The correct term is “The inverse square law of a POINT_SOURCE of light” and a soft-box is not a point source of light, but a small speedlite is a very good approximation. My first lead-acid battery powered electronic flash was a Braun, it had 2 power levels — blinding and vaporising, Luke Skywalker’s sabre was puny by comparison. It had a scale on the top and it would tell you the aperture required for a range of distances, I think it maxed-out at around 15metres, around 45feet. Later I graduated to a thyristor “computerised” flash, the Mecablitz by Metz.

Andrew, I wonder if the following explanation is all we need to explain f-stops:
“The f-stop number is determined by the focal length of the lens divided by the diameter of the aperture.”
This takes the “glass” (clarity, aberration, manufacture, coating, etc.) out of the equation and removes any problem associating f-stop numbers with values less than 1.0. Right?

And if you are talking about transmission, that would be t-stops (the measurement of actual light hitting the sensor) and not f-stops, I believe.

Thanks for the civil response. I was afraid that you would think I was trolling, an all too common development lately. I will do some research and see if I can find something. Will get back to you about it.

I have no explanation, I wonder how they describe 100% transmission. Maybe f1.0 was a theoretical maximum calculated in days past, and technology has surpassed it. If you find out, please share. I will be sure not to make that statement again. But I am pretty sure the maths for the rest is OK.?

Impossible? You wrote: “If a lens could admit 100% of the available light to hit the film/sensor plane then it would be f1.0 and we do not see that as the glass makes it impossible.”

How can we explain the various f 0.95 lenses from Canon, Leica, Voigtlander, Mitakon, Meyer-Optik Goerlitz, etc.? And what about the Carl Zeiss Planar 50mm f/0.7? Or, the Ibelux 40mm f/0.85?

“ISO stands for International Standards Organization.” No, it does not.

I am posting a new reply because although steverumsby pointed this out 8 days ago, the article still has not been updated. This misconception that ISO stands for Int’l Standard Organization continues to be perpetuated by ill-informed writers and YouTubers and it’s annoying. And for you YouTubers, to clarify another misconception, ISO is pronounced eye-so, not eye-es-oh.

From ISO themselves (https://www.iso.org/about-us.html)
“It’s all in the name
Because ‘International Organization for Standardization’ would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), our founders decided to give it the short form ISO. ISO is derived from the Greek isos, meaning equal. Whatever the country, whatever the language, we are always ISO.”

Tony Northrup addressed this in a video: https://www.youtube.com/watch?v=mqk5ln5IC5U
More film speed info: https://en.wikipedia.org/wiki/Film_speed

Thanks in advance for updating your article with correct information.

George is right and the reason that most people struggle with the concept that the higher the f number the lower the amount of light hitting the film/sensor plane. Properly expressed it would be 1/16th or 1/4th but the fraction (ratio) is condensed. If a lens could admit 100% of the available light to hit the film/sensor plane then it would be f1.0 and we do not see that as the glass makes it impossible. But a lens of 1.414 allows 50% of the light to hit the film/sensor plane. This number – 1.414 is the approximate square root of two, so if we want to halve the light again we have an fstop of 1.4×1.4 =2. halve again and we get 2×1.4 =2.8, 2.8×1.4=4 and so on f5.6, f8, f11,f16, f22 and f32, and allof this is because the formula to derive the area of a circle is pi x r-squared. So, ro decrease the amount of light in 50% increments we need to reduce the radius of the aperture by 1/1.4 each step.