Why f/2.8 is the ultimate magic aperture
The f-stop of our new NIKKOR Z 70-180mm f/2.8 lens is the Goldilocks of f-stops for many. So, why is f/2.8 so popular and how can you get the most out of it? Creative director and photographer Dom Salmon explains…
Image-making, whether stills or video, is a deeply personal thing. We all have our favourite settings, techniques, ways of shooting and editing styles. There are as many opinions as there are photographers and videographers. Yet, there is one thing we can almost always agree on: f/2.8 is the magic aperture. But why do so many people say that?
If you ever go to a gathering of cinematographers, you’ll at some point meet someone who will look mistily into the distance and say: ‘f/2.8? Yeah, that’s instant The Godfather.’ * The notion of f/2.8 being the magic aperture for movies is a common one. But how come? It’s certainly used a lot in classic movies, and it wasn’t a totally creative choice, but a practical one, too.
A shot in the dark
Back in the days of film, movie-makers had a problem: to get a low grain image, meaning higher quality for projection on a large screen, you needed a low ISO film. Classic cinema film stock typically sat in the 50-100 range.
But these were not very ‘fast’ films. You needed to throw a lot of light at them to get the exposure you wanted and the most obvious way to do that was to open up your lens to let in more light. But why 2.8? Lenses can go faster than that, so why not go all in with, say, f/1.4? Again, practicality was a big factor.
The focus-puller on movies was always the first to get fired. You could have a perfect take. All the actors hit their marks, the car in the background exploded right on cue and the lead actor made the director cry with their emotive delivery of the killer line. And then… “CUT!”
But… if, when you watched the dailies and the scene wasn’t in focus, it was useless: the focus-puller got their marching orders and you’re a day behind schedule.
So, you could open up beyond f/2.8, but it meant you had a nightmare keeping subjects in focus, especially when they were moving. Remember, at f/1.4 the eyelashes can be sharp but the eye not so much. The focal plane you’ve got to work with is that narrow.
So, again, f/2.8 seemed to be settled on as the best compromise of light to depth-of-field, giving you the most practical focus ‘window’ to work with.
Probably the most prosaic reason all those great cinematographers stopped down to f/2.8 was lens performance. A couple of stops down from full wide, lenses started to play nicer. They were sharper at the frame edge, didn’t vignette as much, had less chromatic aberration and more contrast and ‘3D-ness’.
Look at a film like Taxi Driver. Those incredible night scenes of Travis driving his cab round New York were shot on lenses way open at f/1.4, as Scorsese and cinematographer Michael Chapman needed to get every single ray of light going on to that film stock to see anything. It’s quite ‘soft’ focus, the bokeh of the streetlights is an odd triangular shape, and you can barely see De Niro. It works artistically but, if the whole movie was shot like that, you’d probably think you needed your eyes testing when you came out of the cinema.
So, as you can see, a lot of technical considerations made f/2.8 the ‘hero’ aperture in cinema that it is and explains why you see it across so many movies. However, a lot of that isn’t so relevant for stills, so why is it still a go-to aperture for those, too? Well, great image-makers are always looking to tell a story, whether with a single frame or 60 times a second. And that’s when f/2.8’s spooky magic starts to reveal itself.
Shoot to thrill
f/2.8 is a super-powerful tool in the portrait shooter’s bag of tricks. Fully open, a f/1.4 lens can turn shallow focus into more of an effect. It’s great when used well, but can be a little distracting from your subject – and don’t forget that it’s their story we want to tell. At f/2.8 on a portrait focal length (somewhere between 70-100), you’ll have the tip of the nose to the ears pretty sharp, so you can really engage with your subject, but you’ll start to get beautiful focus fall-off past that.
I’m a huge fan of that look for non-studio portraits, when you capture the whole face sharp but, while you’ve included the background to set the scene, it’s pleasingly ‘in the background’ – people can ‘get’ where the picture was taken, but it doesn’t distract them from your subject.
Street shooting is also great with f/2.8 as it allows you to create real depth and layers of action in your image. People talking with a busy market behind them? To me, that always looks better when the foreground subjects get some focus separation from the background – some shots can simply have too much detail.
In the end, f/2.8 is pleasing to viewers because it mimics the way our eyes look at a scene. Subconsciously, we concentrate and ‘see’ the thing we’re interested in while filtering out the distractions around it. This aperture helps recreate that sensation on a flat photo incredibly well.
As a tip for street shooting, I usually switch my autofocus to favour the centre area. Plus, I recommend you get familiar with ‘back button focus’ and don’t tie your shutter release to the AF. It really puts you in control of your focus.
Now we’ve dug deeper into what f/2.8 can add in terms of emotion when shooting a single image, you can start to see its storytelling power – and it’s a characteristic that’s just as significant and emotive when your image is moving.
Take a single actor, or interviewee, in a frame, talking. It’s one of the simplest set-ups you can have.
A lens all the way open at f/1.4? Suddenly, your viewer loses any sense of where this scene is happening. Is it a real space? Is it a studio? A green screen? A key storytelling element to your scene or interview is lost. Conversely, when everything is super-sharp, our hero literally becomes part of the scenery, because if you focus on everything, you can’t pick out anything. Ultimately, f/2.8 is cinematic because it makes you think more cinematically.
You’ll start asking questions like:
- What lighting style can create real depth between my subject and the background?
- Where should I place the people in my shot to ensure they are the audience’s main focus?
- What camera move can help me totally change this scene without the need for an edit?
- How do I use the background to establish the location without it being distracting?
These aren’t technical problem-solving questions. These are real artistic choices.
An offer you can’t refuse
Low-light performance on a Nikon Z series means you can shoot on low ISO settings in much darker environments than you used to be able to, so f/2.8 can be plenty wide enough, even in challenging locations.
This low-light ability also means less additional light is needed, so maybe a simple reflector, rather than an LED light, can fill in the detail on a person’s face, keeping your scene’s lighting much more natural looking.
With the precision of eye-tracking auto-focus, that f/2.8 depth of field window for sharpness is pretty generous for your camera to keep up with (and in cameras such as the Nikon Z 8, it’s spookily accurate when following action). You’ll very rarely lose an image because of lack of sharpness, so you can really concentrate on the rapport you build with your subject as you shoot, rather than fret about your focus ring.
In turn, for video, you can be confident when moving your camera or your subject (or better still, both), because you know your main focal point is going to look crisp and sharp even at those unforgiving 4K+ resolutions.
High performance f/2.8 is no longer the domain of the big-bucks lens, either. The NIKKOR Z 17-28mm f/2.8 and NIKKOR Z 28-75mm f/2.8 are super-useful zooms at a more affordable level than the pro S versions, but with hugely impressive results.
For a longer focal length, the video results at f/2.8 from the NIKKOR Z 70-180mm f/2.8 are brilliant.
In the end, f/2.8 has become a favourite because it works. It’s the Goldilocks aperture for so many scenarios, whether you’re shooting stills or moving images, and opens up a whole new set of creative choices for you. Try it out and you will, quite literally, see the light.
*Note: The Godfather was actually shot with ‘Super Baltar’ cinema lenses, often at T2.3 (T-stops measuring the amount of light entering cinema lenses rather than f-stops, which measure the size of the aperture), but the point is well made!
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