Some old-school photographers may tell you that you don’t need an autofocus (AF) system in a camera, but there are few that will dispute that a good one can make life much easier – especially if your vision is less than 20:20.
A good AF system will get a subject sharp faster than the blink of an eye and keep it in focus even if it moves. Our friends and guest bloggers at Photoventure take a look at some of the best AF systems out there.
1. Canon EOS-1Dx
While Nikon users swear by the D4 and D4S, professional Canon photographers are just as keen on the EOS-1Dx.
This full-frame camera has 61 AF points on offer, giving slightly more comprehensive coverage than the D4S.
What’s more it can continue to focus when shooting at 12fps, giving one more image every second than the D4S – that could be important when shooting fast moving sport.
Significantly for users of long telephoto lenses with teleconverters, the 1DX can focus with effective maximum apertures as small as f/8, a trick it offered following a firmware upgrade to bring it into line with the Nikon D4S.
The finer points of the AF system aren’t quite as intuitive to set-up as the D4S’s, but there’s lots of control and it works incredibly well delivering sharp images even in very low light.
2. Nikon D4S
Many professional photographers considered the full-frame Nikon D4 to offer the very pinnacle of autofocus performance, so the fact that Nikon managed to improve upon it for the D4S was quite an achievement.
The D4S uses an Advanced version of the Multi-CAM 3500AF module found in the Nikon D4.
This means that it has 51 AF points, but there’s a new Group-area AF mode in addition to the 9-, 21- and 51-point dynamic-area AF and 3D-tracking modes.
This new mode is designed to help when shooting small moving subjects against a high contrast or distracting background, and it works really well.
Nikon also dampened the mirror movement in the D4S and, as well as reducing the viewfinder blackout time, this gives the AF system more time to work between shots.
This, plus the move to Nikon’s Expeed 4 processing engine, enables the AF system to operate when shooting at 11 frames per second (fps).
The D4 could only achieve 10fps with autofocusing.
3. Canon EOS 5D Mark III
Stepping down a level from the 1Dx, the 5D Mark III is the camera of choice for many enthusiast photographers as well as budget or size-minded pros.
However, this camera has the same 61-point wide-area autofocus system as the bigger, more expensive model.
It offers a huge improvement on the Canon EOS 5D Mark II, which had just 15 AF points with only nine being user-selectable.
Of these 61 points, 41 are cross-type and five are dual cross-type points, which is good news for accuracy.
There’s also a dedicated AF menu screen to enable you to specify things such as how quickly it should respond to changes in subject distance.
It’s a great AF system that can be relied upon to get subjects sharp in a range of conditions that challenge lesser cameras.
This SLR has a Dual Pixel CMOS sensor which means that in live view and video mode it can use a combination of contrast and phase detection focusing.
This makes the focusing faster than most other SLRs in live view mode, yet smooth and positive in video mode to deliver high quality footage.
When composing images in the viewfinder, there’s a dedicated phase detection sensor with 19 AF points, all of which are cross-type for greater sensitivity – that’s just like the Canon 7D, which sits above the 70D in Canon’s SLR line-up.
The two cameras’ AF systems aren’t identical, however, as the 70D has three AF point selection modes: Single point AF, Zone AF and 19-point Area AF, whereas the 7D has five, adding Spot AF and AF point expansion to the list.
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