Deep focus, where all elements in an image are in focus, is a technique that is often used in landscape photography and street photography. Here, we learn about 4 factors that affect deep focus. How about trying them in your next photo shoot?

EOS R6 Mark II + RF14-35mm f/4L IS USM @ f/16, 1/20, ISO 125

 

How to deep focus?

“Deep focus” refers to a state where all elements in an image are in focus. You can call it a technique that is the opposite to creating bokeh. To achieve it, you need to maximise the “depth of field” (the area of an image that appears in focus).

The depth of field is controlled by the following 4 factors:

1. Focal length
The depth of field is greater at short focal lengths.

2. Aperture
The depth of field is greater at smaller apertures.

3. Shooting distance
The further the camera from the subject, the larger the depth of field.

4. Depth
This refers to the distance between foreground, medium ground, and background elements. Deep focus is easier to achieve with a flatter scene (less distance between the foreground, and background).

In other words, the easiest way to ensure you achieve deep focus is to:
- Use a wide-angle lens
- Set it at the smallest aperture possible (highest f-stop)
- Position your camera as far away from the subject as possible
- Compose so that the scene has less depth.

Let’s look at examples of each factor.

 

1. Use a shorter focal length

The examples below were shot from the same spot at different focal lengths, but with the same f-stop (f/8). The focus point was kept on the panda soft toy. The buildings in the background are sharp in the 24mm shot, softer in the 47mm shot, and visibly blurred out in the 105mm shot. This shows the depth of field is larger at shorter focal lengths.

All images: EOS R6 Mark II/ RF24-105mm f/4L IS USM @ f/8

 

2. Use a narrower aperture

The images below were shot from the same position with different f-stops. The f/16 image is sharp from the flowers in the foreground to the buildings in the background. Meanwhile, the flowers are out of focus (blurred) in the f/4 image. It’s easier to achieve deep focus with a narrow aperture.

Narrow aperture (f/16)

EOS R6 Mark II/ RF24-105mm f/4L IS USM@ 35mm, f/16

Wider aperture (f/4)

EOS R6 Mark II/ RF24-105mm f/4L IS USM @ 35mm, f/4

 

Pro tips:

 

 

3. Find a camera angle with less depth

A flatter image can be fully in focus even with a shallower depth of field. In the scene below, the arrow sign is close to the background, so we could get everything in focus at f/4 when we shot head-on. However, shooting it from a diagonal angle added depth—that’s why the front and back of the second image are out of focus.

Both images: EOS R6 Mark II/ RF24-105mm f/4L IS USM @ 74mm, f/4

 

4. Shoot further from your subject

The following images were both shot with the same aperture (f/8) and focal length (24mm) but from different shooting distances. In both, the focus was placed on the rock. If you think the background buildings look crisper in the second example, you are right. The difference becomes more obvious when we zoom in—see the crops below!

Shot nearer to the subject

Shot further from the subject

Both examples: EOS R6 Mark II + RF24-105mm f/4L IS USM @ 24mm, f/8

When shooting closer to a subject, increase the f-stop to maintain background sharpness.

 

Level up: Important concepts for deep focusing

1. Focus plane and in-focus area

EOS R50 + RF35mm f/1.4L VCM @ 35mm (56mm equivalent) @ f/1.4

i) Everything to the left and right of the focus point will also be in focus
We put the focus point on the flower. As the camera focuses on a plane, the parts of the bench to the left and right of the flower are in focus too.

ii) The area in front of and behind the focus plane will also be in focus
The area that appears in focus (depth of field) extends in front of and behind the focus plane. While the size of the depth of field depends on the 4 factors we have mentioned, it is usually larger behind the focus plane than in front of it.

Keep these concepts in mind when deciding where to put the AF point!

2. Using a very high f-number reduces image quality

While a narrower aperture helps get more elements in focus, using an aperture that is too narrow could backfire. This is due to an optical phenomenon called ‘diffraction blur’, which makes details look less sharp (“softer”).

This is what happened to the uncorrected f/16 example below, which looks softer than the f/11 example.

The area in the red frame when enlarged
EOS R5/ RF50mm f/1.2L USM @ ISO 100

 

 

3. Focus stacking

It’s not always possible to get the entire image fully in focus in a single shot. You might need to do focus stacking,  a technique that involves taking multiple shots of the same frame with slightly different focusing distances (“focus bracketing) and merging (“stacking”) them to create one final image that is sharp from front to back.

Also see:
Focus Stacking: A Pro Technique Made Simpler with Focus Bracketing

 

Deep focus can help you achieve photos like this!

EOS R8/ RF15-35mm f/2.8L IS USM/ FL: 24mm/ Aperture-priority AE (f/14, 1/125 sec)/ ISO 100/ WB: Auto

A short focal length and narrow aperture to achieve deep focus
This shot is in focus from the grass in the foreground to the mountains at the back. This was achieved by the short focal length and narrow aperture setting.