If you’re a landscape photographer, you want to have the entire scene in focus. But what if want to place attention on a particular subject, amidst the hustle and bustle?
This is where selective focus comes into play. It is a little more complex than only changing your aperture. Read on to find out.
What Is Selective Focus?
Selective focusing is a basic technique. The photographer selects a particular subject or object to focus on. They do this while ignoring every other aspect of the scene. By using a shallow depth of field, that selection can be in sharp focus while the rest blurs away.
By isolating the subject or object, you draw the viewer’s attention to it. This is very helpful in scenes that are busy, distracting or unattractive. For powerful images, try contrasting a sharp object in front of a blurry background.
How To Use Selective Focus?
The out-of-focus areas of an image are just as important as the areas that are in focus. Without them, you couldn’t have a differential focus or selective focus.
Imagine a world where every image showed each scene in perfect focus. How boring that would be!
Luckily for us, manufacturers pour incredible amounts of money into the research and development of lenses. If they didn’t, we’d all be stuck with slow glass, with a focus that wasn’t worth a damn.
Today, we have tack sharp zoom and prime lenses. They also have very precise autofocusing systems. This allows us to capture sharp images constantly.
There are many ways you can use and create a selective focus in your images. Some of these ways are to change your depth of field, use wide-open apertures and long lenses.
You can also separate the subject from the background, move closer to the subject, and change your angle.
Depth of Field
Images that show selective focus have a shallow depth of field. This means that the range of focus is very small. Let’s look at an example with the Canon EF 50mm f/1.2 L USM Lens.
If your subject was 10 feet from the camera, at f/1.2, expect to see a near limit of 9.74 ft and a far limit of 10.3 ft. Everything between these measurements (0.54 ft) will be sharp.
Photographing the same subject with an aperture of f/16 means a near limit of 7.33 ft, a far limit of 15.7 ft and a total of 8.41 ft in focus. These 8 stops of aperture added 7.87 ft of focus into your scene.
What is interesting is the range of focus changes. It depends on the distance of the subject from the camera. You have 0.54 ft of focus at f/1.2 when the subject is 10 ft away.
If the subject moved to 30 ft away, the amount of focus rises to 4.97 ft, over nine times larger.
This shows that the closer a subject is to the camera, the easier is it to have a selective focus.
A wide open aperture places a smaller focal range on a scene. This means less of the scene, subject or object is in focus. An f/1.2 has the possibility to capture the eyes of a person in focus while keeping the nose and ears out-of-focus.
A narrow aperture places more of the scene in focus. Anything above f/16 will place everything in your scene in focus. But, there are issues for consideration.
The other is that faster lenses can suffer from chromatic aberrations.
Longer lenses affect your ability to capture scenes with selective focusing. Some telephoto lenses, especially the lower end versions, have variable apertures.
Let’s use the Canon EF 70-300 mm f/4-5.6 as an example of the maths. At 70 mm, you can use the f/4 aperture. 70 divided by 4 gives us 17.5 mm.
By zooming all the way in, we go from a 70 mm to 300 mm focal length. The images you capture magnify by 4.3%. At 300 mm, your widest aperture is f/5.6, where the diameter is 5.4 mm.
But why can’t the lens be f/3.5 throughout the zoom range? At 300 mm, an f/4 aperture would be 75 mm.
This is too big to fit into the slim body of the lens. There isn’t enough space for this wider aperture.
A longer zoom means a smaller field of view and, in this case, a narrower aperture. If using the 300 mm focal length, capturing an object 100 ft away with an aperture of f/5.6, you’ll achieve a 7.22 ft total depth of field.
Any lens can soften the background in any given scene. This is as long as the background and your distance to the subject will allow it.
The closer you get to a subject, the blurrier it will get. The same goes for extending the distance between the subject and the background.
Your choice in lens is important. A wide angle lens is going to have trouble placing areas in your scene out of focus.
It will soften enough that your sharp subject will stand out.
If you’re looking to reduce your depth of field, you don’t need to buy a very expensive telephoto lens.
A Canon 24-70 mm lens with extension tubes is a cheaper way to break into those longer focal lengths.
Extension tubes are inexpensive cylinders that contain no optics. They attach between your lens and camera body, shortening the minimum focus distance.
This is due to moving the lens farther from the sensor. As the tube contains no glass, the quality of the image is not compromised.
The more costly extension tubes are stackable. The more you stack, the longer the focal length becomes. On top of this, you can focus closer and create a shallower depth of field.
But, there is a downside. The further the lens is from the sensor, reduces the amount of light entering your scene.
As you need more light, you may need to raise your aperture.
Separate the Main Subject and Background
Your perspective in photography is very important. It isn’t only the aperture that affects your depth of field.
Consider the three positions, if you will. Where the camera is placed, where the object/subject is and how far away your background is situated.
By moving closer to your subject, you reduce your total depth of field. As we looked at before, the total focal length changes, even at the mid-range apertures.
Let’s say you are using the Canon EF 50mm f/1.2 L USM Lens. If your subject was 30 feet from the camera, at f/5.6, expect to see a near limit of 21.6 ft and a far limit of 49.3 ft.
Everything between these measurements (27.7 ft) will be sharp.
Photographing the same subject with a distance of 1.47 ft (minimum focusing distance) means a near limit of 1.45 ft, a far limit of 1.5 ft with a total of 0.05 ft in focus.
By bringing your subject much closer to the camera reduces the depth of field. If your object had a background two meters behind them, at 30 ft away they would both be in focus.
At 1.47 ft away from the camera, the background would be blurry.
Change Shooting Angle
The angle in which you shoot from is very important in obtaining a selective focus. If you capture objects at the same distance from the camera and sensor plane, they will all be in focus.
If you change your position and thus angle, you can add interest.
Everyone seems to have that very cliche shot of a line of people (usually the police) at a protest or demonstration.
The photographer has chosen to stand 170° (or 10°) from the line, allowing them to see police officers start close and fall away towards the background.
Three or four people in – the focus fails. By showing one person in focus, they add interest to the scene through selective focus.
If the photographer stood straight on to the police line and captured them at a 90° angle, it would have a very different effect.
You need to press the depth-of-field preview button if not using the widest aperture.
This will show you what you will record, while darkening the view, making it difficult to see. The best solution to this is to use your live-view screen as it shows you the scene as it will be captured.
The only downside is that LCD screens can wash out in bright sunlight.
A mirrorless camera uses an electronic viewfinder, which shows an exact image as the camera will capture it. Also, it isn’t affected by ambient light.
Macro photography is one field that really needs to harness the power of selective focus. And it’s down to two main reasons.
The second reason is down to your camera’s settings. Flowers and insects, unless either dead or out of their outdoor habitat, are going to move.
Flowers dance in the breeze and insects, well they do what they want. A moving object needs a fast shutter speed.
Don’t worry. If you want to place the entire subject in a sharp focus, there is focus stacking.
Most of the time you decide to use a selective focus is because the background isn’t attractive, or it’s too distracting.
Sometimes, it isn’t possible to move to a better location. You can use a selective focus to blur the background and reduce it’s important.
Having two different types of patterns could distract the viewer from the subject.
On top of this tip, keep strong elements away from corners. They prove to be distracting and helps the viewer’s eyes lead to the edge of the frame, and then out of the scene.
Getting your audience’s attention to leave your image is something you don’t want to do.
One Setting at a Time
As we have seen, a selective focus is compromised of many elements. The best place to start, even before setting your camera up, is your choice of subject and then the background.
Having a clear idea of what you want to photograph is the first step.
For example, if you were to photograph earrings on a person for marketing reasons, the earrings are the most important part.
Next comes the concept of the shoot. Why are you photographing the earrings?
Is it to show what they are? In that case, a close-up shot of them on a woman’s ear is what is needed. A selective focus softens the rest of the face and blurs the background.
If it is more of a lifestyle shoot, then a situational image is needed.
By capturing a wider shot, you include the environment. The environment shows the viewer what the earrings are good for, usually high-end dining and relaxation.
The selective focus will fall on the earrings first and show the woman wearing them, and any other elements needed.
Your aperture will depend on your purpose. An aperture of f/1.2-f/2.8 is wide enough to show the earrings without the background. The closer you are, the narrower the aperture can be.
For more situational shots, a mid-range aperture like f/5.6 is needed.