Bickering on whose lens is faster...the frontings of the lensmaker...

"f0.95 is faster than f1.0"...An air of silence...because no lens manufacturer, in their right mind, will come out and say that! They will just print that on their latest super duper chunk of glass and let the reviewers and public awe takeover. Eventually, and the lensmaker knows this, everyone of those fast lens enthusiasts(and who isn't...) out there will gravitate towards their f0.95 lens rather.

So how much faster is f0.95 than f1.0 and also why is it that Canon and Nikon shows f1.2 on their fast lenses and cameras while Sony uses f1.3 rather and all of them deemed to be 1/3 stop faster than f1.4?

Figure 1 following shows a spreadsheet of the simplified calculations of aperture values of a 50mm lens(not based on actual measurements of relative apertures which would involved locating and measuring the entrance pupil). The spreadsheet shows the actual definition of relative aperture based on the opening of the entrance pupil which will be expected to be found. It gives a theoretical entrance pupil area needed to support the desired relative aperture values. Canon, Nikon and Sony stopped bickering a long time ago and would even agree that f1.2 and f1.3 are equal for all intents and purposes and deemed to be 1/3 of a stop faster than f1.4.

Figure 1

Of note in figure 1 is that relative aperture maxes out at f0.50 for any lens with perfect transmittance. This is covered in most optical theory text under illuminance.

Of course a mathematician would have noted the inconsistencies in the aperture values of accuracy to 1 decimal place for aperture values slower than f1.0 and to 2 decimal places for values faster than f1.0. This, the optics theory physicist would argue, is due to an ever increasing rate of the entrance pupil area change(larger) as values of aperture drops below f1.0 towards the theoretical limit of f0.50.

At f1.2, entrance pupil area is 17% larger than that at f1.3, about one sixth of a stop and yet both are deemed equal or of no noticeable nor consequential difference(for all intents and purposes...) to the modern digital sensors of today.

Now comes the lamer, f0.95 and f1.0 only differs by 10, well ok, 11% in entrance pupil area, effectively one tenth of a stop. This is where when you see f0.95, it really begs to be no different from f1.0.

Thank you Canon, Voigtländer and Leica as well as clever rebranders of security camera lenses for making this blog post possible.      ;-)