I know that. It’s just I’m allergic for that for some reason. Sorry for mentioning.
George
Hi @George
Wow - that’s some piece of work!
Not to denigrate it at all, but have you seen the writings of George Douvos?
Apart from the complicated scientific stuff, he has created an iOS app that does all the hard stuff when I’m shooting critical subjects.
@JoJu mentioned my “f/10 mantra” but that is a miscomprehension of what I wrote.
Using the principles that George Douvos outlines, I found that what others call CoC, he refers to as the blur spot diameter and is based (with digital sensors) on the size of a square of four pixels. In my case, the Nikon D850 has a pixel size of 4.34µm, so a blur spot size of 8.68µm (I round that up to 10µm)
Doing all this “stuff” is all about reducing diffraction blur as much as possible so, with a blur spot of 10µm, this gives a minimum aperture without diffraction of f/5.
But there is a problem with that. With a 28mm lens, you would have to focus at a hyperfocal distance of 21m, but that only gives a diffraction free DoF from 10.5m to infinity, which could be useful but rather restrictive if you want the immediate foreground in focus.
Doubling the blur spot diameter to 20µm is where I get the f/10 from, which allows me a hyperfocal distance of 5.28m and a nearest distance of only 2.64m - which is amazingly useful for landscapes with a foreground subject.
Of course, this is not the only aperture that I use, especially if I want to restrict the DoF but, if I do want “from here to infinity” shots, it does mean I minimise diffraction and, since doing that, I often get comments on my prints from folks who think they were taken with an LF camera, especially if I have used the Fine Contrast sliders to bring out detail.
My goal was not to calculate the dof but to visualize the coc outside the dof and the development of the coc based on a certain focus distance.
There’re many dof calcualtors with different layouts but none showing the coc outside the dof. And that’s an essential part of isolation as you meant. This tool can show you why the background is a little blurred or much blurred.
Once the code is written in an object oriented environment it’s easy to add a different sensor size so you can compare two sensor sizes.
Something for your club? 
Looking at the file dates I worked on it 4 years ago. A
George
@Joanna while you posted a thread about “isolation in composition”, you just do the opposite and talking widely about your f/10 dogma to get as much DoF as you can squeeze out of the mediocre 28-300 (which you let still unaltered as 28-200 under your images…)
You completely ignore the effect of the enlarging scale, the sharpening you’re using and so much more (like the surface of the paper you’re printing on) for the benefit of impractical, theoretical math mumbo jumbo.
So be it, I no longer care and also no longer participate in a fake pseudo debate. Talking about one thing at first, just to divert to the complete opposite, this kind of distraction lately starts to become more apparent in various posts, mostly from people beyond a certain age.
I find @Wlodek’s contribution much more to the point than your f/5.6 wannabe-isolations. Which in my eyes are already a collection of isolated objects, but no valid demonstration of the effects wide-open apertures will have. Most of them would look just the same if you’d taken them with f/10 
The coc is solely lens based. Sensor is not involved. Just looking for an example I found this How to calculate the Depth of Field (DoF) with the Specim hyperspectral cameras? - Specim
Look at the range of the dof and then you have the image distance of the dof on the sensor side. Just calculate now the subject distance for those 2 lines.
George
Ah I see. Thanks for the explanation.
I hadn’t realised you were a code-head. The app looks like Windows - did you use C# in Visual Studio? I spent around seven years doing a major project for accounting, stock control, sales, etc for company in Ireland. But, since then, I discover Xcode for macOS, which is totally free and have been developing macOS and iOS apps.
OK back to photography 
I really like the tonal transitions of those black and white images and the low depth of field adds to that smoothness.
Personally, I did find surprisingly find very few pictures except portraits, where I used a low depth of field as a compositional element and where I liked the results better than with a larger depth of field. And somehow even for portraits, I started using more and more depth of field instead of less, and paying more attention on the background.
A picture like this could work, if there was something interesting going on on seat number 12 
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And here a counter example, using other elements than depth of field for composition:
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I tried to explain but you obviously missed the point (again).
That is because, at that time, I was using 28-200mm lens, which I later replaced with the 28-300.
The point of talking about CoC, blur spot, etc was to illustrate that, by using an aperture that avoids diffraction, you get even sharper images
Don’t knock it matey - we all get there sooner or later.
When you get old enough to know what you are talking about, you’ll realise that, for certain subjects, at certain focal lengths and at certain distances, you don’t need ultra-large apertures to isolate subjects. Maybe at shorter focal lengths, they come in useful but when you are further away from your subject you simply don’t need such a large aperture…
For example…
| Focal length | Distance | Aperture | DoF |
|---|---|---|---|
| 35mm | 0.5m | f/1.8 | 12mm |
| 400mm | 3m | f/8 | 11mm |
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Oh, I just adore both of these. That is composition on steroids 
Ah yes, that long forgotten part of an image that you only ever see when you’ve taken the shot and can’t get back to take it again 
Oh thanks, that’s quite some compliment.
That was the idea.
If I told you, I’d have to kill you
Think again. You can see I’m looking down, so the background is the sand on the beach.
Yup, result of the edge of the deck and no room up or down due to sail booms, etc.
Actually, the central “subject” is a man swimming.
Once again, these were mainly technical demos of DoF control rather than artistic masterpieces. If any of them make a great image, that’s a bonus.
Nearly all of my wide open aperture photos are taken for light conditions, some for more artistic reason.
One of them was this one. I think the aperture was too wide.
28-70 70mm 2.8
George
The aperture was too wide for what? If your goal was to experiment with isolating the tree trunk and the broken shards of wood on top of it from the background, what aperture would you have preferred using? What about it made you question the aperture? If isolation was my goal, I probably would have used an f/2 or faster lens to further isolate the stump from the background.
Mark
I would have liked to make some more pictures with different apertures so I could choose between them. This picture isn’t meant to isolate the tree stump on the foreground. The background is an essential part of the subject. It was the subject once one can say.
This lens doesn’t go below 2.8.
George
Given the closeness of the tree trunk and the distance to the background try using at last f/11 if you want everything in focus. But that is the opposite of isolation which is the topic of this thread.
Mark
It’s not a question to get it in focus. But out of focus can be in more gradients.
George
Well, I guess you will have to play with various apertures until you get results you like.
Mark
A few ways to exhibit the subject with focus layers (DoF) and …
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warm-cold & form contrast
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color quality & contrast
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diffusion & color
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subdued
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shape & color
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luminosity & contrast
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stylish & color
( all taken at: 300 mm, except #5: 190 mm / #7: 20 mm )
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I like the ashtray photo. Soft glass edges play well with soft focus transition, creating a kind of magic with this combination of colors.
What lens did you use?
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