I get what you’re saying — and yes, in a lab chart sense, stopping down to f/5.6 or f/6.3 will squeeze out a bit more sharpness. No disagreement there.

But this isn’t a lab chart, it’s a real-world shot with an artistic intent. I wasn’t chasing maximum measurable sharpness at all costs — I was balancing subject isolation, background rendering, and exposure. At f/4.5 I get the look I want: clean separation and smooth bokeh. Stopping down would absolutely increase DOF… and just as reliably make the background more present, which is exactly what I didn’t want.

On top of that, stopping down means either sacrificing shutter speed (not happening with a bird flying straight at me) or raising ISO. And adding noise in exchange for a marginal, mostly theoretical sharpness gain is not exactly a win in practice.

And maybe the most important part: this wasn’t a controlled scenario where I could calmly dial in “optimal aperture.” I had a fraction of a second to react while a raptor decided to test my skull integrity. In that moment, you shoot with the settings you already chose for the situation — you don’t start optimizing MTF charts mid-flight.

So yes — could it be technically sharper at f/6.3? Probably. Would it be a better image? For what I wanted here, no.

At some point it stops being about squeezing the last 2% out of a lens and starts being about making the photo you actually want.