I have just received the email about - UPDATED: TUTORIAL ON DIFFRACTION & PHOTOGRAPHY
What a load of inaccurate information, there is no actually validation or references, just an expression of an opinion
The exact value of the diffraction-limited aperture is often a contentious topic amongst photographers.
NO just read
The Manual of Photography and Digital Imaging
Elizabeth Allen , Sophie Triantaphillidou PhD (professor of photography)
or the earlier edition
Manual of Photography, Ninth Edition (Media Manual)
Ralph Jacobson PhD ASIS FRIC FBIPP CChem (Author), Sidney Ray BSc MSc ASIS HonFBIPP FMPA HonFRPS (Author), Geoffrey G Attridge Bsc PhD ASIS FRPS (Author), Norman Axford BSc (Author)
And the four authors listed are the lecturers I had when doing my BSc in Photography - the answer is there in the text book.
Search out and look at the images for the Nikon D800 and D800e - with and with out Anti-Aliasing - the difference is very noticeable.
The information is in these text books written by subject matter experts, not by amateurs or lay photographers as this site appears to be.
They sum up in a few worlds what is a very complex subject of lens design the different aberrations and diffraction. The key point is really that the different aberrations can be minimised but never totally corrected, in particular chromatic aberration.
These are always greater than the effect of diffraction in the real world. To put it in context and just considering the accuracy that a camera lens would need to be built too (to show diffraction). A lens would have to be built to a smaller margin of error than half the wavelength of light. If you say why half the wavelength? because of destructive interference.
The build accuracy, for a diffraction limited lens, has been suggested at a quarter the wave length of light (and remember the wave length of light is a range of wave lengths (some suggest a tenth)) and other errors even smaller.
Let me put it another way if you buy a lens taking into account the profit made by the shop, the distributor and the manufacturer how much money actually goes into making the components? lets say 30% is reasonable - do you really expect your lens of a few hundred £ or $ is built to that standard?
Certainly any zoom lens has to make a number of compromises to just to function at all and therefore it becomes impossible to conceive that aberrations are reduced below that of diffraction.
No manufacture is selling their lenses as being 'diffraction limited' or purporting to be of a design and build quality where optical aberrations are so reduced that the only factor influencing the quality is diffraction.
Plus if you are looking at your pictures as in Jpeg don't forget to add in those effects as well.
so the myth of 'Diffraction' - yes diffraction exists
when is it obvious? - when all other aberrations have been corrected for
are all aberrations corrected in the camera lenses available today - no because the level of build quality required plus the optical quality of the components would be prohibitively expensive if actually possible.
If you want correct information - sorry you need to go to the textbook written by subject matter experts, however they are text books so therefore not actually easy to understand.
I am sure this post will attract criticism but sorry the information is available in university text books which thanks to the web can be found second-hand. If you can not get the basics right how will you actually understand photography.
Particularly :- The exact value of the diffraction-limited aperture is often a contentious topic amongst photographers.
I was taught this 36 years ago why is there any debate about the best aperture? (it is in the text books) - because the web can proliferate non peer reviewed 'information' which is repeated so many times people believe it is fact.
Unfortunately for photography it suffers from many amateurs expressing opinions on matters they are ill equipped to understand. Or professionals in other fields taking basic theoretical facts and applying them to the real world ignoring the real world factors.
Now the only person who I would accept as being able to correct the above is Sidney Ray who has written the definitive text book on camera lenses, or a lens designer from say Nikon or Canon. Because unless you actually work in this field you wont have the specialist knowledge to correct any error I have made.