One of the key new features of Apple's latest iPhones is the ability to adjust the 'bokeh effect' on portrait images, after they've been taken. But, as well as letting you adjust the intensity of the effect, the function has been enhanced to more accurately represent the bokeh characteristics of a real lens, rather than just trying to blur the background.

Every time you shoot an image using the 52mm-equivalent F2.4 portrait camera on the iPhone Xs you have the choice of editing the bokeh effect. This brings up a scale marked in F-numbers. This may sound like Apple just borrowing an interface from the real-world (a process called skeuomorphism), but it goes beyond this: the company says it's modeled the bokeh characteristics to mimic the behavior of a Zeiss lens.

We thought we'd put this to the test: how convincingly does the iPhone Xs resemble a real-world lens? Is the F-number scale anything more than a pastiche? To find out, we shot the Xs alongside the Nikkor 58mm F1.4, mounted on a full frame camera.

iPhone Xs vs Nikon 58mm at F1.4

iPhone Xs image processed as 'F1.4' Nikkor 58mm at F1.4

Scaling the Nikon image down to the same width, you can see the bokeh is around the right size:

Then, when you look at the bokeh off-center, you'll see it develops an elongated 'cat-eye' effect.

iPhone Xs vs Nikon 58mm at F8

iPhone Xs image processed as 'F8' Nikkor 58mm at F8

Just as with the real lens, the cat-eye effect diminishes as you 'stop down.' And Apple has given its bokeh a smooth, fairly gaussian look, rather than the slightly bright-edged bokeh that Nikon has produced, being constrained by the limitations of things such as glass and physics.

Unlike the 'real' camera, the iPhone's sharpness doesn't always drop-off smoothly: for instance it's blurred both shoulders and the subject's scarf, despite the nearer being in a similar plane to the face.

However, while this doesn't always looks natural, the phone is intentionally ensuring that the subject's face remains entirely in focus, which is usually a good thing. And, unlike the $1600 Nikkor lens, it doesn't become a little soft and dreamy when set to 'F1.4.'

Equally, because the iPhone isn't actually changing its aperture, you don't find yourself with less light if you want more depth of field (the iPhone portrait camera's actual depth of field is F15 equivalent, so there's plenty that's in focus in the underlying 'native' image), so you don't have to worry so much about camera shake or subject movement.

The end result isn't going to convince anyone if they look too closely (the processing has cut-off some of the fine hairs, for instance), but for social media use, it's hard to deny that the effect is impressive. And we have to assume this technology will only get smarter and more powerful in future generations.