How to autofocus with SLR

Lead: No matter you are a senior photographer or a junior photographer, you are not even interested in photography, but as long as you pick up any equipment to take pictures, it is closely related to one action, that is, focusing. Let me talk about the use of SLR autofocus.

Nowadays, digital SLR cameras have good auto-focusing function, and also provide manual focusing, so that everyone behind the lens can play more creativity. As the name implies, autofocus is a way to automatically drive the electric focusing device to focus after being processed by the image processor algorithm, while manual focusing is a way to adjust the camera lens by manually turning the focusing ring to make the photos clear. The letter AF stands for auto focus and MF stands for manual focus.

What is autofocus?

Auto-focusing is a process in which the camera automatically moves the lens to focus after accurately measuring the distance by using infrared, ultrasonic and laser. Focusing can show different performance effects on different subjects, and the intelligence of autofocus can help most photographers focus quickly and effectively, which is a great help for whites.

? Different focus positions can produce different effects.

Autofocus can generally be divided into multi-point focusing and single-point focusing. Multi-focus function or area focus function is easier and easier for beginners. In addition to setting the focus position, you can also set the focus range. When the focus center is not set in the center of the picture, you can use multi-point focusing to directly cover an area with the focus point, so that the camera can automatically identify it.

On a camera, multiple focuses can cover an area.

Single-focus mode, especially the free-moving single-focus mode, requires some artificial free movement, but it is a very convenient shooting mode after smooth use. As long as the camera focuses on the subject by moving up, down, left and right, the camera will automatically focus on you.

? Switch to free-moving single-point focus (the bracketed area focus box is single-point focus)

Move the focus by pressing the up, down, left and right buttons.

A camera with touch screen operation function can also focus through the touch screen.

Photos taken in single-point focusing mode under autofocus can reflect shallow depth of field and highlight the subject. In single-point focusing mode, it is best to match a lens with medium and long focal length. The focal length of the lens should be above 85mm, and the aperture of the lens should be above F5.6, so that it is easier to take excellent photos in single-point focusing mode.

How to use manual focusing?

Since autofocus is so convenient, is it necessary to carry out troublesome' manual focusing'? Don't all photographers who are particularly professional and awesome play manual focusing? Let's not say that there will be mistakes in using autofocus in some cases, and details will be mentioned later. And from my personal experience, using manual mode in Xiaobai period can make you slow down, feel the charm of careful shooting, and feel a sense of accomplishment in gradually clear images, which is far more satisfying than relying on the number of more shots taken by continuous shooting to pick out clear photos.

Let's talk about how to do manual focusing. Let's start with something simple. Use the real-time view on the screen to help you focus manually accurately;

? First, set the lens side to MF.

Press this button to switch to the live view on the screen.

? Put your finger on the focus ring; Rotating lens focusing ring

Check the focus through the screen. If you are not sure whether the focus is accurate, you can use the zoom-in button to enlarge the approximate focus area, and then turn the focus ring. Every time the zoom button is pressed, the magnification will cycle between 1 times, 5 times, 10 times and cancel the magnification.

Press the zoom-in button

? ? Turn the focus ring to focus at the magnification of 1 times, 5 times and 10 times respectively.

It is also impossible to twist the focus ring in one step. When the picture gradually becomes clear, you need to twist the focus ring repeatedly left and right to confirm whether you are in focus, and the enlargement of the focus area picture is only to make you more clear and intuitive to confirm whether you are in focus accurately.

Then cancel the magnification and complete the focusing.

Repeated focusing by magnifying can greatly improve the accuracy of white people, but when you are skilled in manual focusing, you will feel that this method is somewhat inefficient. Try shooting with a viewfinder. Although I can't enlarge the focus area by using the viewfinder, I believe I can master the focus skillfully through repeated practice. But what if I can't see the picture in the viewfinder clearly because of myopia? Is it wrong or is your eyesight wrong?

At this time, you can adjust the diopter to suit your vision and turn this wheel.

When do I focus manually?

We already know the convenience of automatic focusing and the necessity of manual focusing, so under what specific circumstances is it better to use manual focusing? The most suitable situation is to use manual focusing when the contrast of the scene in the picture is small and not high. Simply put, the picture is messy, the focus subject is too close to the background color, or in a low light environment.

? For example, I want to focus on the blue center of the ship, but the scenery is chaotic, and autofocus is always recognized elsewhere.

Another example is that I want to focus on the yellow chessboard, but it is too close to the color of the yellow chessboard, and the autofocus fails.

At this time, manual focusing does not need to rely on the camera itself to identify, but on your own perception. As long as you can focus accurately through the above methods, even if you zoom in first and then focus slowly, at least you can shoot the subject that you want to express, instead of letting the camera compete blindly, which is very useful for small white to shoot still life.

Also, when shooting macro, manual focusing also has advantages over automatic focusing. Macro photography has a large aperture and a shallow depth of field, which makes it difficult for the camera to identify the subject through autofocus, and a slight movement may cause focus deviation. At this time, manual focusing will become accurate and controllable.

F 1.8 macro, large aperture, suitable for manual focusing.

Some special macro lenses also have the function of full-time manual focusing, which can be completed manually in real time, and fine-tuned manually on the basis of automation, which brings great convenience to macro photography. However, it is worth noting that if the lens does not support full-time manual focusing, manual rotation of the focus ring in the auto-focusing state will obviously feel great damping, so please use it with caution to avoid destroying the damping.

In addition, if you want to take a landscape photo with a large depth of field, you can also use manual focusing. There is a saying called. Hyperfocal distance? , is the shortest focusing distance that the lens can focus when keeping the object at infinity with acceptable sharpness, or refers to the focusing distance that all subjects have acceptable sharpness when the lens focuses at infinity. Simply put, it is to be able to take clear landscape photos from far to near.

The pictures taken with hyperfocal distance come from the Internet.

The characteristic of photography in hyperfocal distance is that you can take clear photos far and near without focusing on a certain place. At this time, shooting the scene can better represent the near and far scenes, and can also avoid the possible out-of-focus caused by autofocus. The specific method is to manually focus to hyperfocal distance for a long distance or infinity.

You can also use manual focusing when taking pictures of glass. Although taking pictures through the glass is not an ideal shooting condition, when you fly or visit the aquarium, you are likely to encounter the pictures you want to capture with your camera. When shooting through the glass, manual focusing can avoid focusing on stains or reflections on the glass, which is convenient for correct focusing.

When flying, you can take pictures through the glass by manual focusing. It comes from the Internet.