Dave,
When I made the post, I already knew that you would disagree. An interesting article on megapixels was published in the New York Times in 2007 (I think that is before they began posting fake news ). He did a blinded study and concluded that 6-8 megapixels was sufficient. If this were true, I don't know why anyone would pay US $50,000 for a Phase One IQ4 that is advertised on the opening page of this forum. In any case, LuLa is happy to accept their advertising fee.
Lloyd Chambers (Diglloyd) has written extensively on the effects of diffraction on his pay web site. In a study with the Nikon D7100 (a 24 MP crop frame whose pixel density would result in 56 MP in a full frame camera) with the Zeiss 135 mm f/2 plan apo (perhaps the sharpest available lens at that time) he noted dulling of the image at f/8, even with aggressive deconvolution sharpening. A dull haze was noted at f/11 and f/16 and f/22 showed severe degradation.
I have done my own tests with this lens with my Nikon D850 using Bart Vanderwolf's sinusoidal Siemen's star. Wilth this target, resolution at a MTF of about 10% is proportional to the diameter of the extinction radius. These images are considerably cropped from the full frame to show the area of interest. At f/4 the system resolves to Nyquist, 102 lp/mm with good contrast. Deconvolution sharpening with FocusMagic improves contrast. At f/22 resolution drops to 72 lp/mm with low contrast. FocusMagic can improve contrast, but resolution remains at 72 lp/mm.
[snip]
Proper deconvolution sharpening can partially reverse diffraction, but not completely as shown by my test and by Diglloyd's work.
Of course, you will say that proper deconvolution was not applied. What algorithm and PSF do you use?
Cheers,
Bill
Hi Bill, well you totally lost me there after the first sentence, as I am more than happy to steer well clear of falling down into that kind of in-depth analytical rabbit hole, which I think sort of proves the sentiments outlined of my original post, which is that I think going into this type of analytical depth, is completely at odds with the requirements for your average Joe photographer these days and is to all intents and purposes, totally unnecessary for improving the aesthetic quality of our images, and which I also think can actually become a severe hindrance to it if you let things like this clutter your mind.
Here is an image a took a couple of nights ago, I was sat in the house watching some rubbish on TV and thought no, I am going out with my camera instead, so grabbed the camera and one wide angle zoom lens. I then went down to my local patch and without a thought in my head (perhaps the tweeting of birds or something as equally mindless), where I just setup in a spot I hadn't shot before (that was my only compositional choice BTW) and grabbed a few frames, before going back to the car for a cuppa with a couple of white chocolate chunky biscuits - which will be the death of me because I just can't stop eating them). The lens was already set on f/16, the camera on fully manual with daylight white balance and single shot mode. I stuck on my 10 stop ND, focussed on the rock near to the vertical rocky outcrop about 2/5ths up the frame on the left. I then wound up the exposure time to 30 secs and the ISO to give me a half stop underexposed, I then pressed the remote switch and continued listening to the bird song in my head and all-in-all, the shot didn't turn out too bad. Is it sharp enough? Who knows, it certainly looks OK to me and would still look OK printed out a 48 inch or even more. Is there a focal point or a central point of interest? Not really, but again I am OK with that, because when I look at it now, I realise that it represents my mood more than it does anything else and if I judge the image in this way, then yes it is a perfectly good image.
So how did I sharpen it? Well I haven't, although I did add some clarity by running it through ACR for a second time. I then duplicated the layer and added some despeckling to the upper layer and then created a sharpness mask for that layer, so that only the areas without detail (sea and sky etc) got the despeckling. Took me about half an hour to finish it and that included dust spotting.
I suppose what I am saying Bill, is that yes you are correct in everything you are saying, but for me it isn't my thing and I have been doing this long enough to realise that I really don't need it - you could say I have managed to find my comfy place and where I no longer have to worry or even think about such things as deconvolution sharpening, Airy disc diameters, or diffraction, because my reasonably priced equipment is good enough, that I can empty my head and let my emotions do the work.
All the best Bill and thank you for allowing me to realise by describing it to you here, how I now work and how happy I have become with it
Dave