Here's the difference the wider aperture of the iPhone 18 Pro makes

Alongside a variable aperture lens, the main camera of the iPhone 18 Pro also opens up to a wider aperture than its predecessors. Apple has been promoting this as enabling a shallower depth of field for portraits and similar shots.

The difference, however, is less than a stop, and it’s been unclear how much real life difference this would make on such a small sensor, so I set out to put it to the test …

It’s important to draw a distinction between the optical shallow depth of field enabled by a wide aperture lens and the artificial effect enabled by Portrait mode.

With the latter, Apple uses computational photography and the LiDAR sensor to work out where the subject ends and the background begins in order to apply an artificial blur. The quality of this has improved dramatically over the years, but that’s not what we’re testing here. All of the background blur seen in the sample photos was achieved optically by using the widest possible aperture of f/1.48.

The iPhone 17 Pro had a widest aperture of f/1.78. This is essentially indistinguishable from f/1.8, which is the second-widest aperture available on the iPhone 18 Pro. What I’ve done here is to use the new manual controls available to take the same photo twice, once at f/1.8 and again at f/1.48, in order to compare the difference.

There are, however, three other optical factors affecting the amount of background blur of any photo:

To eliminate these variables, all of the photos are taken at the same focal length (the main camera, which is the only one with a variable aperture), the same framing (ie. same background), and at the same distance. There’s a few seconds gap between the photos as I adjust the aperture, so they are not 100% identical, but both myself and my subject stood still to ensure both were taken at exactly the same distance even if he turned his head between shots.

With these controls in place, any difference in background blur is due entirely to the aperture.

All of the test shots are portraits – that is, head-and-shoulder shots – as this is the type of photo for which wide apertures are most commonly used (hence the name Apple applies to the artificial effect available in Portrait mode).

Additionally, by getting close enough to shoot head and shoulders, we are maximizing the degree of background blur we would expect to see. This makes for the best basis for comparing the shots, versus wider ones where the degree of blur may be harder to assess.

Finally, I’ve included a few shots with graduated backgrounds, so you can see how the focus falls away with distance.

With all of that pre-amble out of the way, let’s take a look at the results. Move the slider all the way to the right to view the f/1.78 version, to the left to view the f/1.48 shot, and anywhere you like to compare different parts of the image.

I think this shot provides the clearest illustration of the impact, as it contains background elements ranging from a few feet to around quarter of a mile:

The fountain is the closest element, at around 8-10 feet, and we can see a noticeable difference here. The tree is about 30 feet away, and the difference is smaller but still distinct. The pagoda is maybe 70 feet away, and the difference remains clear but a bit less pronounced. Once we reach the more distant elements – the bridge and buildings on the far side of the river – the difference is more subtle: we can clearly see it when actively looking for it, but I don’t think most people would notice unprompted.

In terms of practical benefit, the shot below is a good illustration. With the f/1.78 aperture, I’d describe the separation of Chris from the background as a little marginal in places, for example, the person eating in the restaurant top right and the section of building top-right of his head. With the wider aperture, the separation is definitely improved.

I’d wondered how much difference we could expect to see from a relatively small change, and now I have my answer. The significance of the difference is something you can judge for yourself from the sample shots; personally, I’d describe it as relatively subtle but in truth bigger than I’d expected – and enough to be useful in some situations. Please share your own thoughts in the comments.

The wider aperture is not the only benefit of the new lens. There are other situations in which it can be useful to take manual control of the variable aperture, and I’ll be looking at these in a follow-up piece.