Photography Basics #4: Digital Auto Focus vs Manual Focus

Michael Sand
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Autofocus

Vs. Manual Focus

Both auto focus and manual focus have their pros and cons. It pretty much depends on what your reason is for using one or the other. If you shooting in a hurry, or you are completely new at photography, the autofocus mode is a good option for you. Auto focus gets the job done quicker than manual focus and is the better option for people who want the shoot the "decisive moment."

Understanding Manual Focus

Everything is manual in the manual focus. Manual focus is most often referred to as traditional focus. You use the lens ring to focus. This means that you have to be careful. The goal is to get the lens positioned at the right distance from the subject. The focus ring allows for precision.

If you don’t have a very unique or interesting subject in your frame, you might be better off leaving your camera on auto focus. With auto focus, your camera will focus on the largest object in the frame. The auto focus feature will get the job done quickly.

Peripheral vision eliminates most of the guess work in manual focus. When the ring on the lens goes to the focus point, you can safely press the shutter button. When you press the shutter, the image in the view finder is going to go into sharpness at the center. While the closest focus does not necessarily mean it is in focus at the center.

What is Autofocus?

Autofocus refers to the camera's method of setting what is in focus, in a photo. Most of the modern (non-film) cameras feature autofocus. The Autofocus (AF) systems have better detection, speed and accuracy when compared to the manual focus systems. This is helpful in capturing a perfectly sharp image.

Basically, the camera's viewfinder helps in focusing on the objects at a specific range. In other words, a camera can focus objects at a specific distance, by capturing the image through the lens.

This is possible through the Autofocus feature. The camera focuses the image onto the Image Sensor and the Autofocus system reads the amount of light, passing through the lens onto the image sensor. Then, the system helps in determining what needs to be focused. Generally, depending on how quickly the camera focuses on an object determines the speed of the camera.

How Does Autofocus Work?

You switch on the autofocus (AF) feature on your DSLR camera and are ready to start shooting. You then notice the auto-focus does not lock on to your subject in the frame.

A camera with a small sensor has a fixed lens and uses a contrast-detection method to focus. Contrast-detection method is used by many more compact cameras and DSLRs with the AF assist lamp.

For now, let us concentrate on DSLR cameras with a large sensor and interchangeable lenses that may have a problem with the autofocus.

When using a DSLR camera with a large sensor and interchangeable lenses, autofocus works by locking on to the contrast of your subject in the frame.

When autofocus is working, it is basically locking on to the contrast of your subject in the frame.

The AF system uses two types of autofocus, phase-detection on DSLRs with relatively small sensors and contrast-detection on cameras with a larger sensor.

On DSLRs with a relatively small sensor, the autofocus is based on an optical process, which measures contrast.

However, on cameras with a large sensor, the autofocus is based on an electro-magnetic process, which measures the contrast.

Phase-detection autofocuses uses an array of high-resolution sensors and adjusts itself to different focal lengths. This ensures that it is very responsive.

Manual Focus

Auto focus is based on algorithms that analyze the distance between the camera and the object being photographed. It then provides a setting, usually a number like 4m, that is the setting for auto focus.

When the camera is in auto focus mode, it's not necessary to touch the lens at all. The photographer simply has to compose the image and press the shutter. Everything is taken care of by the camera and lens. On some cameras, the photographer can select the specific object to be in focus, in case the photographer knows the distance to the object, which is less frequently the case.

Auto focus is very useful and practical, but not always ideal. It has a limited range, requires good lighting, and it's not very easy to control or get a correct focus, especially when shooting with wide angle. If there's not enough light, or the subject's colors are complex, it can have trouble focusing.

What is Manual Focus?

In contrast to the auto focus option, manual focus lets you select the lens, and set the focal point required to take the shot. You may not be able to instantly find the exact focus if using a very small aperture. As such, it is recommended to use a tripod and liveview.

Some people may find it hard to go from auto to manual focus, but the transition should be rewarding and you will be able to shoot the exact focusing point you need. You will also increase your understanding of how the focal point affects the overall look of the photo.

Manual focus is something you can start using as soon as you reach the intermediate level of photography. It is very useful for shooting landscapes with a wide aperture setting.

How Does Manual Focus Work?

Manual focus means the goal is to get to a certain focus point after turning the focus ring. The purpose of doing this is to get the optimal sharpness.

A good example of this would be using a macro lens in order to get to a certain object in focus.

Before digital cameras became affordable and popular, every camera had a focus ring. As such, manual focus was much more common and it still remains so especially amongst the sports and action photographers.

Auto Focus vs Manual Focus: Which is Better?

Auto focus is an invaluable feature for cameras. When you want to take a picture of your family you just press the auto focus button and voila, you have a picture of your family.

Manual focus is good for certain situations. For example, if you are taking pictures of a subject that is close to the camera or a subject that is stationary. Bear in mind that it’s always easier to focus on a stationary object.

Auto focus is also good for taking pictures if you are moving the camera and the subject is stationary. The auto focus tracks the object, unlike manual focus, which locks you in a single point.

This also comes in useful when taking a photo of many subjects that are spread out over a large area.

For Macro Shots

Manual Focusing is Best.

Manual focusing has always been an option for photographers. But with the ability to touch-up photos in an imaging program on a computer, the use of manual focus is on the decline. Now your camera can rack your focus for you.

If you’re an expert photographer it may be hard to imagine that there are people out there who don’t know how to adjust a camera’s focus manually. But it’s true! Cameras automatically focus your shots for you. You need to turn their Auto Focus features off for everything besides landscape shots.

Auto focus may be fine for the everyday family photo, but it’s certainly not a blast for macro shots. For macro photography such as flower photography you need to learn how to focus manually. And once you learn this technique, you will have the edge over all those point-and-shoot cameras automatically focusing on an average shot. Plus, your photos will have a depth of field they couldn’t quite capture.

You'll need to pick a focal point before starting. If you are taking a close-up of a flower use the center of the flower. If you're taking a photo of an insect, focus on its body. Afterward, make sure the background is defocused.

For Action Shots

Automatic Focus is Out and Manual Focus is in!

Digital cameras now days have a built in auto focus mechanism. It can be very convenient and fast but cannot always be trusted. So which is better? Automatic or manual focus?

On cameras that don’t have an auto focus, like the DSLR, the only way to focus your shots is by using the manual focus setting.

Manual focus is a complex but effective art. It focuses your lens to a specific distance depending on what you want to shoot.

Automatic focus is used by most novice photographers. It may be a little hard to focus using the automatic focus feature the first time.

But once you have mastered it, you can shoot really nice detail shots.

Overcorrecting an over focused image may be hard to salvage but is unlikely to be impossible. Overcorrecting an under focused image is next to impossible.

So try to focus on the subject, not the background.

For Portrait Shots

Most Pro-Ranked Cameras Use Manual Focus.

According to David Hobby, the key moments before the shot are much more important than the shot itself.

This is something I have learned from the first day switching from an amateur to a professional photographer, the second being the importance of the edges.

In David’s words, the “golden ratio” of photography is *%% – A skilled photographer, a valuable software, a well-lit scene, and a properly exposed shot.

Surprisingly, the last part, exposure, is often incorrectly evaluated in photography. It may sound crazy, but many amateurs make it a point not to learn anything about exposure and rely on trial and error.

A manual, long and cropped portrait shot.

This approach works OK for a beginner and it’s definitely the right approach for anyone who is already happy with the results achieved.

Only if you’re aiming for something better and higher, or if you want to improve beyond your level, you’ll need to understand exposure, and the right way of exposing the shot.

For Landscape Shots

Where is the Focus Zone?

Digital auto focus is faster, but does it get the shot right every time?

In the early days of DSLR, when digital auto focus was in its nascent stage, it was not even close to being able to match the precision of manual focus. Manual focus still prevails as the most accurate method of bringing the subject of the image into focus.

There is a sweet spot on the Z axis of the lens, which is at its sharpest. And to get the sharpest image possible, you should have the focus spot exactly on that spot. By adjusting both the aperture and the focus ring on the lens, you can bring the sweet spot into focus.

While digital auto focus allows you to focus on the entire image area, manual focus allows you to focus on the subject exactly in the same manner as you do when you look through a pair of binoculars.

In a landscape photo, the sweet spot should be at the part of an image where you see the foreground and/or the background sharply. Your camera should be focused precisely on that plane, at the sweet spot of the lens.

This ensures the sharpest possible image for a landscape shot instead of a blurry one.

For Shots with Little Light

Focus Manually

Digital auto focus uses auto focusing sensors on your camera body to precisely focus in on your subject based on the distance you have set with your focus settings and lens.

But when the light is low, or you are shooting at night or in the dark, your auto focus becomes useless, so you need to resort to manual focus.

When using manual focus, you see a scale on the lens that you use to adjust the focusing. In most cases, it can be either at the top of the lens or somewhere in the middle.

When you zero in on a certain object, a distance button pops up, with which you can set focus. It's important to remember that it will be really close to this point when you take the actual shot.

When using autofocus, you have the on-camera flash to help you achieve proper focus.

Using manual focus is a bit trickier, but if it means getting the shot, it's totally worth it!