Where Should I Focus?
A common question we get on our photo workshops is ‘where do I focus?’ When the subject is obvious the answer is easy—focus on the subject! But this question more often comes up in the context of urban landscape and architecture photography. So, let’s narrow the focus of this article to that genre and go into some focusing techniques as well.
First a bit about Depth of Field
To answer the question of where to focus, we must first understand Depth of Field, or DOF. A quick overview of DOF: the aperture setting affects how much of the scene will be in focus. A common misconception (held surprisingly often by clients on our workshops) is that some apertures are used for close focusing and others are used for focusing on distant objects. This is incorrect! Any aperture can be used to focus at any distance. Instead, what the aperture affects is how ‘deep’ the focus is.
Essentially, a wider aperture (smaller f number, such as f/2) will result in a shallow DOF. A narrower aperture (bigger f number, such as f/16) will result in a deeper DOF. Keep in mind that ‘deeper’ does not mean farther ‘away from the camera.’ Rather, it means farther away from the point of focus.
The second thing that affects DOF is the focus distance that the lens is set to. For example, if I focus on an object 30 centimeters in front of the camera, the DOF might be from 28 centimeters to 36 centimeters. This means the focus area is only about 8 centimeters in depth. However, if I focus on an object 5 meters away, the DOF might be between 2 meters and 8 meters, resulting in a DOF of 6 meters. Keep in mind, this is regardless of the aperture setting—the closer you focus, the narrower the DOF will be.
Of course, these two effects operate simultaneously. Meaning that if we focus close and use a wide aperture then then the DOF will be razor thin—only a few centimeters. However, if we focus far away and set a narrow aperture, then the DOF might be many tens of meters in depth. For a landscape photograph (urban or otherwise), this second circumstance is usually ideal!
So, with all that, we can deduce where to focus if we want to maximize DOF for urban landscapes—on an object rather far from the camera. However, there is a bit more to it, and for that we should think about how the camera focuses.
What Cameras Focus on Best
Modern cameras focus using one of two systems: phase detect or contrast detect. I will not go into the technical details or the merits of each system. All you need to know is that these methods work better when focusing on details or areas of high contrast. The easier to discern those details are, the more accurately and quickly the camera can focus.
Examples of great focusing targets are signs, text, brick walls, road markings, repetitive patterns, and so on. What all these things have in common is distinct areas of contrast. Some less than stellar focusing targets are trees, bright lights, neon signs, glass, fuzzy things, etc. These objects all lack some definition and have features that blend together even at different distances. The worst things to focus on have uniform colors and lack details, such as bare asphalt, single-color surfaces, empty patches of sky, glowing surfaces, and so on.
Obviously, all cameras are a bit different and some handle these things better or worse. But in general, try to focus on high contrast areas in the image. Combining what we learned above about DOF, we also know that these areas should be a good distance from the camera.
All that should give you a good idea of where to focus, but let’s go beyond that—manual focus.
Manual Focusing with the LCD Screen
Auto-focus is great on most cameras these days, but when I’m using a tripod I like to focus manually. The reason is that I can be 100% sure that the focus is perfectly accurate, and I get enjoyment out of slowing down and doing things manually. However, most cameras these days are not so manual focus friendly when using the viewfinder (old cameras had split prisms in the viewfinder to aid manual focusing). On the other hand, digital cameras are great for manual focusing when using the LCD in live view mode.
On most mirrorless cameras, you already have the image on the back LCD, but on SLRs you’ll have to go to live view mode. Once you’re looking at the photo on the back LCD, you can zoom in the picture. This does not mean zooming with the lens, but rather zooming the picture itself. Most cameras have a dedicated button which allows you to do this (look for a pair of buttons with + and – symbols).
Once you zoom in the picture, you should also be able to move the image around. Find an object with details and contrast, such a railing, a sign, or a post in the part of the scene where you want to focus. Then, make sure you’re on manual focus, and simply turn the focusing ring on the lens. I recommend doing this with the aperture wide open (at its lowest setting, i.e. the smallest f number). This way you can really see the focus change as you rotate the focusing ring. Once you’ve set the focus, you can set your aperture back to f/8 or f/11 (or whatever aperture is needed for the shot). And that’s it! Tack sharp focus done manually—shoot away to your heart’s content.
TL;DR — So, What’s the Gist of It?
Okay, okay… so, to recap, when shooting an urban landscape scene, I tend to focus on objects that are far away from the camera, but not necessarily the farthest objects. I also choose to focus on objects with lots of contrast and details that are easy to distinguish. Whether focusing manually or automatically, high contrast details make focusing easier and more accurate. And in general, when shooting on a tripod, I prefer manual focus with the aid of the LCD screen. If you want to learn all this and more, just join our Tokyo By Night Photo Adventure. Now get out there and challenge your eye!