Notice you always mention that you go for large apertures and was going to ask before out of interest. Why does every shot need to be with a large aperture, it is not needed all the time is it?
I was actually kidding when I said I shoot at f0.95-2 and that anything f2.8 shows diffraction![]()
Hardly ever shoot at 2.8, unless I am shooting a group with lots of depths, usually shoot at f/1.6
Why? Are you 20ft away?
no i'm not 20ft away
why would I have to be 20ft away?
Because at 10ft the DOF for a 50mm @ f/1.6 is ~ 1 ft which is rather thin for "usually."
I'm assuming something like the 50mm to get that fast of an aperture...if it's 85mm then the DOF is ~1/3.
a) most peoples heads are less than 15cm in depth so I don't need anywhere near a foot to get a sharp image
b) group shots I'm often at 1.6 35mm which is a ton of DOF
c) I position my subjects on the same plane so I rarely need more than 10-15cm even for groups
a) Most people's heads are less than 6" (15cm) nose to back?
c) 10-15cm DOF for groups?



There are many reasons why a lens shouldn't be used wide open..
-a lens is never at it's sharpest wide open
-most lenses loose some contrast/clarity wide open
-a very thin DOF can cause AF "misses"
-a very thin DOF can make subject movement problematic
-w/in the DOF there is only one point of maximum sharpness...stretching that point a little can really help.
Taking a f/1.4 and stopping down 2 stops to 2.8 only doubles the DOF and that increase in dof is divided between front and back. The lens will be sharper with better clarity for possibly no real penalty.
Not using the lens wide open will maximize image quality. Having a bit more DOF will make life easier.
In your fist example the DOF is ~4"' so a little over 1" in front, and a little less than 3" behind. Stopped down to f/2.8 it would only increase to ~8", so ~3" in front and ~5" behind. If for some reason that gain in DOF is problematic you could have moved the subject a little further from the BG.
Better yet would be to use a longer lens from further away...The same aperture would give the same DOF (for FOV captured) but the BG would "appear" to be blurrier and there would be less of the BG in the image. (But I don't think either would have been necessary.)
In your second image your up to ~16" DOF which is reasonable...The lens is still probably not at it's best but how much that matters depends on the particular lens...They're kind of close to a distracting BG so I can understand the wide aperture. But a longer lens from further would probably have been better.
In the last image you're down to ~2" DOF (I'm just "swagging" all of these DOF's). But again, a longer lens from further stopped down a little would give the same "look" with less of the BG. And @ 6ft you're starting to get into "perspective distortion" distances.



FWIW, I like the images....
...........
I don't shoot a lot primes a lot and I don't shoot Canon. I am familiar with the Sig 85 f/1.4 and it IS excellent..technically better than my Zeiss. So there are differences... but in reality they're pretty minor.
If the point is separation from BG, then there are other ways of doing it...I would say "better ways." I'll go from ISO 100-400 without a second though before I trade off on my desired aperture...
You obviously are convinced wide open is the way to go...you love primes and you probably love "bokeh." So I'm probably not going to change your mind.
All I can say is "always" shooting wide open is not great idea.
I don't want to make this "personal" in any way, but I will say that quite a few of your example images don't look particularly sharp from what I can tell...it's hard to say at these small sizes, but generally if they don't seem particularly sharp at small size then they only look worse larger. Not all of them though. And what matters more is capturing personality and "communicating," which you are obviously very good at.
If it makes any difference, I've been a photographer for over 35yrs and once upon a time I made my living from it... I'm not just trying to be difficult.

f2.8?
I rarely use such small apertures. All you're going to get is diffraction and front to back DoF.
tosh
I was actually kidding when I said I shoot at f0.95-2 and that anything f2.8 shows diffraction![]()
This is a totally irrelevant discussion, if we are not also discussing format, shooting distance and focal length
What do you shoot at f2.8 and why?
If your only concerned with DOF. CA, ghosting/Lens flare, IQ, contrast, etc are all also affected by aperture regardless of the other factors. And regardless of the lens, it's not going to be it's best wide open unless it was specifically designed to be it's best wide open like the Nikon 58mm f/1.2 "nocturnal" lens.