CHOOSE THE RIGHT AF MODE
Photography week|February 23, 2023
We all know what autofocus is, but how does it work? And what modes work best in different situations? Matthew Richards explains
CHOOSE THE RIGHT AF MODE

All DSLRs have a conventional phase-detection autofocus module. The main reflex mirror is partially translucent, so light can pass through it and be directed by a second mirror, downwards to the autofocus module. This module contains a number of autofocus points, each with its own set of sensors. The sensors compare the light entering from opposite sides of the lens; if the light is in phase, the lens is properly focused; if the sensors measure a difference in phase, they can tell the lens in which direction focus needs to be adjusted, and by how much. The module keeps on checking while the lens is adjusting, until optimum focus is achieved. 

A basic DSLR typically has fairly few phase-detection autofocus points. In the case of Nikon cameras, for example (the principles here apply to all makes of camera, and to mirrorless models too), the D3500 has 11 AF points in total, of which only the central point is cross-type. A cross-type sensor enables greater accuracy, as it’s able to resolve detail in both horizontal and vertical planes, instead of just one or the other.

More advanced cameras tend to have more AF points. The Nikon D5600 has 39 points (9 cross-type), the D7500 and D750 have 51 points (15 cross-type) and the D500 and D850 have 153 points (99 cross-type). Greater numbers of AF points enable you to select positions at finer increments, over a larger area of the frame, as well as tracking moving subjects more accurately.

この記事は Photography week の February 23, 2023 版に掲載されています。

7 日間の Magzter GOLD 無料トライアルを開始して、何千もの厳選されたプレミアム ストーリー、9,000 以上の雑誌や新聞にアクセスしてください。

この記事は Photography week の February 23, 2023 版に掲載されています。

7 日間の Magzter GOLD 無料トライアルを開始して、何千もの厳選されたプレミアム ストーリー、9,000 以上の雑誌や新聞にアクセスしてください。

PHOTOGRAPHY WEEKのその他の記事すべて表示
CALIBRATE YOUR COLOURS
Photography week

CALIBRATE YOUR COLOURS

James Paterson reveals how he captures stunningly colourful sunsets by using this secret weapon

time-read
1 min  |
September 26, 2024
ABSTRACT PORTRAITS
Photography week

ABSTRACT PORTRAITS

Mike Harris shows you how to use slow shutter speeds and multiple exposures to capture a series of motion-blur portraits

time-read
3 分  |
September 26, 2024
BREATHTAKNG IMAGES FROM ABOVE AND BELOW THE WAVES
Photography week

BREATHTAKNG IMAGES FROM ABOVE AND BELOW THE WAVES

A final hit of inspiraton: Ocean Photographer of the Year reveals stunning winning photos

time-read
1 min  |
September 26, 2024
THE ULTIMATE GUIDE TO AUTUMN
Photography week

THE ULTIMATE GUIDE TO AUTUMN

James Abbott reveals the secrets to capturing amazing images during the most eye-catching season of the year

time-read
2 分  |
September 26, 2024
CANON UNVEILS NEW PORTABLE, FULLY-WIRELESS PHOTO PRINTER
Photography week

CANON UNVEILS NEW PORTABLE, FULLY-WIRELESS PHOTO PRINTER

The Selphy QX20 is ideal for quickly printing your smartphone snaps on the go

time-read
1 min  |
September 26, 2024
FUJINON GF120MM F4 MACRO R LM OIS WR
Photography week

FUJINON GF120MM F4 MACRO R LM OIS WR

This powerful medium-format lens is ideally suited to extreme close-ups

time-read
4 分  |
September 12, 2024
HOW TO...CLEAN UP A SCENE WITH AI
Photography week

HOW TO...CLEAN UP A SCENE WITH AI

James Paterson shows you how the AI-powered Remove Tool can revolutionise your retouching

time-read
1 min  |
September 12, 2024
SHOOT AN '80S PORTRAIT
Photography week

SHOOT AN '80S PORTRAIT

Jason Parnell-Brookes recreates the neon look of the 1980s using torches and hollow acrylic rods

time-read
4 分  |
September 12, 2024
THE BEST MONOCHROME IMAGE OF 2024 IS A REAL CRACKER
Photography week

THE BEST MONOCHROME IMAGE OF 2024 IS A REAL CRACKER

Black and White Photo Awards announces stunning selection of winning images

time-read
1 min  |
September 12, 2024
88 TIPS FOR GREAT BABY PHOTOS
Photography week

88 TIPS FOR GREAT BABY PHOTOS

From lighting to posing and pacifying, here's how you get the perfect shot

time-read
10+ 分  |
September 12, 2024