Photography Basics: Digital Auto Focus vs Manual Focus

Achieving the correct focus can mean the difference between taking a good shot and a bad one. When your camera correctly focuses on a scene it results in a clear, sharp image. However, focusing on the wrong area will make your picture blurry and unfocused. If you’re a DSLR camera owner, it’s likely that your camera and lens or lenses will have both autofocus and manual focus capabilities. Some older lenses will have fairly slow and clunky autofocus motors, whereas more modern ones are quick and quiet. When choosing between digital autofocus vs manual focus, you have to determine which gives you more creative control and better results in your photos. We’ll examine the merits of each, and when to use them.Auto Focus vs Manual Focus

Autofocus


What is Autofocus?

As you may have guessed, autofocus mode is where the camera does the focusing work automatically. Depending on your settings, this can mean you have little control over what the camera ends up focusing on. You can usually set different focal points in the frame to focus on, but the rest is driven by various sensors in the camera. There are often three different modes you can select from; one-shot, continuous and automatic. Let’s look at each in a bit of detail:

  • One-shot: this keeps the focus on the area you’ve determined for just one shot. It’s mainly used if you’re shooting a subject that is stationary.
  • Continuous: in continuous mode, the autofocus will track your subject through a range of shots and motion. This is particularly useful if you’re taking photos of a moving subject.
  • Automatic: if you need a setting that sits somewhere between the two modes, automatic is probably the right choice. It’s useful for when you’re unsure if your subject will suddenly move or not.

How Does Autofocus Work?

In a manual focus camera, movements to the lens ring adjust the angle of two mirrors. The two images this produces will eventually line up, bringing the scene into focus. Autofocus works on this same principle, however instead of the user judging when the image is in focus, the camera uses an electronic sensor to do the same job.

The sensor compares the data from the two mirrors to determine where the images line up, and therefore how far away the subject is. This result then allows the camera to make adjustments to the lens. Another method of determining how far away a subject is, is to use ultrasound waves in the same way as sonar.

Modern DSLRs will use a slightly different method. A sensor examines the image produced in the viewfinder to find out if it’s sharp and in focus. If not, the camera will make adjustments to the lens until the image comes into focus. It will then go past this point, to ensure there isn’t another focal length at which the image is sharp. Although autofocus is a convenient and quick way of focusing, it does take some of the control out of the user’s hands.

To use autofocus, follow the below steps:

  • Set your autofocus mode; one-shot, continuous or automatic.
  • Find the object or scene you want to photography and point the lens in the direction you want.
  • Set the focus point if you want to focus on an area that isn’t at the center of the frame.
  • Press the shutter release halfway down. This will then make the lens adjust itself to focus on your desired point.
  • Fully press the shutter release to take the picture.

Manual Focus


What is Manual Focus?

Manual focus gives the user all of the control when it comes to focusing the image. This is done by adjusting the lens. Whilst holding the camera and looking through the viewfinder, your other hand will twist the ring of the lens. Fine adjustments can make a big difference, so you’ll need to make smaller movements. Your left hand will both support the lens and make the adjustments. Be aware that you could cause a fair amount of camera shake if you don’t hold everything correctly; you palm should cradle the lens, and your fingers should make the movements.

Because of the fine movements involved with manual focus, it’s sometimes hard to tell exactly when your scene or subject is in focus. To give yourself a better chance of seeing this, try and use the viewfinder to make the initial focus. This not only cuts glare on a sunny day, but it also means you’re as close to the detail as possible.

How Does Manual Focus Work?

A DSLR camera uses a lens and internal mirrors to direct light onto a digital sensor. This then produces an image. However, much like the human eye, if the lens isn’t focused, the final result will be blurry and out of focus. To combat this, lenses are adjustable in order to focus on subjects that are a variety of distances away. A lens has a focus ring, which can be turned to make focusing adjustments.

The movements of the focus ring adjust the angle of the mirrors inside the camera’s body.  Through the viewfinder, you can then see when the images from the two mirrors line up, allowing you find out how far away a subject is, and bringing it into focus. Your lens will likely have distance markers on its barrel that go up to infinity. This should help you focus on objects depending on how far away they are from you.

Below are some tips for using manual focus:

  • If you’re trying to shoot action shots of a potentially moving subject, try and pre-focus the lens ahead of time. This means you won’t miss any of the action whilst you’re desperately trying to focus.
  • Don’t be afraid to use the camera-assisted autofocus. This will quite often be a display that’s visible through the viewfinder. It will show when it thinks you’re perfectly in focus, as well as give indications as to which way you need to adjust to get in focus.
  • Use the viewfinder to get your initial focus in, and then use live view on your LCD screen to zoom in on the image to ensure all parts are in focus.
  • Practice a lot; this will help you get a feel for when a shot is in focus.

Auto Focus vs Manual Focus: Which is Better?


Although autofocus is hugely convenient, there are often times when it’s simply not quite right. After all, the camera can’t interpret data in the same way that you can. Below are some instances when manual focus could be chosen over autofocus:

For Macro Shots

When you’re trying to focus on a subject up close, making small manual adjustments can often be beneficial. You can get the focus exactly as you want it, picking out details that the autofocus can’t see. You need to be precise, but you can afford to take the time to be so.

For Action Shots

Although it’s tricky to both track and focus on a moving target, you can often preempt an action shot if you know it is coming. By manually focusing on a point that you know your target is going to pass through, you can ensure that when the time comes you’ll be ready. In manual focus mode, this will prevent the camera making any last minute adjustments, ensuring you don’t miss the shot.

For Portrait Shots

For photographing a portrait, it’s crucial that facial features, particularly the eye, are in sharp focus. To avoid any misjudgment from your camera, use manual focus to make sure you have it exactly right before taking the photo.

For Landscape Shots

When you’re taking a picture of a wide vista, it’s important that everything is in focus. Because there are often different distances to account for, autofocus can let some of these points slip out of focus. By making manual adjustments, you can ensure that your shot is as sharp as it is to your eye.

For Shots with Little Light

If your lighting is bad, it’s going to be hard for the camera’s autofocus sensor to know what to focus on. It may just end up cycling through focal lengths in the vain hope of finding something. Although some cameras have focus lamps to help with this, they’re often not that effective. Use manual focus to get the shot you want in poor lighting.

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