I think you might be under a misconception that f11 is an absolute value universally applicable, irrespectively for all cameras and all lenses and all sensors, but have it your way if you so wish but that is not the case.
The example above where given to show that the quality of the shot ( not the depth of field!) of the cheap 50-230 stopped down at 22 (plenty of diffraction according to your paradigm) at its maximum focal length was not far off the quality of the shot of the 55-200 at 200mm stopped down at ONLY f8 ( not yet any diffraction, always according to your paradigm).
If the “ diffraction” riddled image of the 50-230mm going anywhere past f11 would have been so bad as you say it should get, at 22 should have been terrible and unusable. No?....No!
Click on the pictures, they will expand even more and THEN you tell me if the 50-230mm at 230mm, f 22, produces an unusable image!
Clearly, it isn’t! That is why I published for all to see the graphic and empiric examples given by the Fuji own entertaining lens evaluation system ( truthful, I hope, although one could suspect that fuji would naturally be interested in selling the more expensive of the two lenses)
However, be happy! I don’t have anything to gain from convincing you if you don ’t want to be convinced.
For the benefit of others who might want to ascertain whether this lens offers " enough playground” ( the only comparable lens the 55-200, would, however offer only one stop more “ playground”) or not.
That’s how I understand the problem.
What happens to a 8 or 15 a 28 or 50mm, where diffraction ( which by the way starts immediately as you start closing the aperture, which also controls some aberrations, will be affecting resolution reducing the quality of an image at some stage) might very well start reducing resolution at values next to F11 ( ore even 8 for that matter!) but that is not the same in a longer lens where it might start above that value ( or for a larger format where it might even start below that value!)
Because diffraction is caused by physical size of the aperture which at some point becomes too small to transmit light in a straight line and bends parallel rays... but this is a relative phenomenon, not an absolute one.
there are lenses which, because of their focal length, are not made to not have a maximum aperture higher than 8 or even higher but can be stopped down to values somewhat past f11 because they are long lenses.
from wikipedia ( a little more scientific article than photozone) https://en.wikipedia.org/wiki/Diffraction-limited_system
“ In a digital camera, diffraction effects interact with the effects of the regular pixel grid. The combined effect of the different parts of an optical system is determined by the convolution of the point spread functions (PSF). The point spread function of a diffraction limited lens is simply the Airy disc. The point spread function of the camera, otherwise called the instrument response function (IRF) can be approximated by a rectangle function, with a width equivalent to the pixel pitch. A more complete derivation of the modulation transfer function (derived from the PSF) of image sensors is given by Fliegel.[3] Whatever the exact instrument response function we may note that it is largely independent of the f-number of the lens. Thus at different f-numbers a camera may operate in three different regimes, as follows:
in the case where the spread of the IRF is small with respect to the spread of the diffraction PSF, in which case the system may be said to be essentially diffraction limited (so long as the lens itself is diffraction limited). in the case where the spread of the diffraction PSF is small with respect to the IRF, in which case the system is instrument limited. in the case where the spread of the PSF and IRF are of the same order of magnitude, in which case both impact the available resolution of the system.
The spread of the diffraction-limited PSF is approximated by the diameter of the first null of the Airy disk,
where λ is the wavelength of the light and N is the f-number of the imaging optics. For f/8 and green (0.5 μm wavelength) light, d = 9.76 μm. This is of the same order of magnitude as the pixel size for the majority of commercially available 'full frame' (43mm sensor diagonal) cameras and so these will operate in regime 3 for f-numbers around 8 (few lenses are close to diffraction limited at f-numbers smaller than 8). Cameras with smaller sensors will tend to have smaller pixels, but their lenses will be designed for use at smaller f-numbers and it is likely that they will also operate in regime 3 for those f-numbers for which their lenses are diffraction limited...."
So, certainly f8 or 11 are limits for most lenses but it is more likely to be 8 for a wideangle and perhaps 16 for a tele.
But again, look at the picture at 230mm at 22, is it fuzzy? Click on the picture, it expands even more!
Large format film cameras are a good example ( although their use on film was possible because film is more forgiving for curved rays of light not traveling in a “ straight” line than a sensor is, that has to be said!)
At one time the majority of lenses ( starting at 135mm to way above 480mm) had a maximum aperture of 5.6 but some, apochromatic lenses had values of f 9 , their best operating values always exceeded f11 because they were long lenses with relative large apertures ( remember the F number is not an absolute dimension but it is a ratio you change one part of the ratio the other part has to change too, longer focal length at the same F value means a wider diameter ).
This lens 480mm, had a starting aperture number at 8.4 and closed until f66, do you really thing that couldn’t give diffraction acceptable images past F11?
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