Diffraction Effects (Example Photos)

Started Nov 27, 2011 | Discussions thread
James Bligh Senior Member • Posts: 2,087
I presumed the same condition as Thom Hogan observed diffraction applied.

Lance B wrote:

James Bligh wrote:

In D3 & D700 diffraction sets in around F16.

In D3X diffraction sets in around F8 & F11.

In D800 if it is 36 MP FF I guess diffraction will set in around F5.6 & F8.

It depends on the print or image size and how far away you view it. It is a very broadbrush statement to say that diffraction sets in at a particular aperture as it depends on many factors like viewing distance, eyesight, print/display size etc. Look at Cambridge Colour's site for a calculator.


As written in the other thread with regards to diffraction limitations, a 36 Mp full frame (35mm) sensor would start to be diffraction limited at f/11 or more but not at f/8 given a 36" print/display, at standard viewing distances, which the article claims is 25cm or 10 inches and that is far too close for a 36inch print/display. A more realistic viewing distance for a 92cm or 36inch print/display would more likely be closer to 1mt or 40inches. At this size and vewing distance that equates to a diffraction limit of f22, which is plenty of DOF. Even at a viewing distance of 50cm or 25inches (which I think is too close) that equates to a diffraction limit of f13 which is still big DOF in my books, depending on camera to subject distances. A more realistic distance might be 75cm and therefore an aperture of about f16 diffraction limitation.

However, a more realistic normal print/display for most of us at say, A3+, or 485mm (20inches) and a viewing distance of say 50cm (25inches) results in a diffraction limit of f22. This size dsiplay relates to many computer screens and large home based printers.

Looking at my computer screen, it is 21inch and I sit at about 60-70cm away from it and I would say that is about as close as I'd want to sit to that size screen. Even a 24" screen would be about as close as I'd say most would want to be as well. So, at 24" display, and 70cm, then I would say that diffraction would not be an issue to at least f18. Even if we allow for a screen to show more detail, I think f16 would still be enough.

So, for a FF 36Mp sensor, it would seem that you can still shoot at high f numbers like f16 or more as the viewing distances are such for a given print size that it means that diffraction is not an issue and even at the cusp of diffraction limits, as the article states, there is more to it than straight diffraction as many other factors come into play. If we go over 36Mp for FF, then diffraction may be a limitation, but again it is very dependant on viewing distances.

BTW diffraction is a gradual thing (See Thom Hogan's D3X review.) so you need some margin of error in prediction.




Yes I understand there are many variables, viewing distance, size of image etc. When I said the statement I presumed the same condition as Thom Hogan observed diffraction in his tests applied. It is my mistake that I didn't mention it. What Thom Hogan said and what I am saying is we should be aware and cautious of diffraction when we take picture especially with high pixel density cameras. Lastly too many numbers in your writing makes me dizzy.

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