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Thursday, February 14, 2013

AF vs AF-S Lenses. Which to Get?

I will be trying to generalize on a topic that cannot really be generalized. When we compare lenses, the comparison and the conclusions reached usually make sense only in a closed group. That is, comparing lens A to lens B to lens C, we try to see which one does what best. However, I have had many discussions with many photographers regarding today's topic, and so I decided to give you my opinion - as always, hoping to help you reach an informative purchasing decision!

"Between an AF and an AF-S lens, which one should I get?"

The Basics
AF lenses are those bit older Nikkor lenses that require a Nikon camera body with a focus motor. These lenses have a screw which is driven by a shaft protruding slightly from the camera body. AF-S lenses have a built-in focus motor, and can be used either with motorized or non-motorized cameras. AF-S lenses are the future; as far as I know, there are no longer any AF lenses produced. But there are hordes of them in the used market. And sometimes, you can get a screaming deal for one of them

AF Nikkor 50mm f/1.8. Less than half of what the new AF-S 50mm f/1.8 costs, but as good (and even better in some ways)

Pros and Cons
In a nutshell, here is a short list with some of the main points.

AF lenses
+ cheaper than similar AF-S lenses
+ in most (but not all) cases, AF lenses also have aperture rings (can be important for cross-system compatibility, and also some applications as macro with extension rings)
+ sometimes, an AF lens is your only choice; AF-S models do not necessarily exist (yet).

- if your camera doesn't have a focusing motor, you can't have autofocus
- noisier autofocus than AF-S lenses
- future of motorized bodies maybe not a given

AF-S lenses
+ they can be used with all modern cameras, whether these have focus motor or not
+ modern technology, no worries about future compatibility
+ silent and often fast autofocus, with (usually) instant manual focus override (no need to flip switches)

- more expensive than AF lenses
- lack of aperture ring can be a problem in some specific cases (see AF lenses above)
- I have no extensive data to support this, but from personal experience, it feels as if AF-S lenses aren't built to the same quality standards. I've had more AF-S lens failures than AF

No aperture ring (left) vs aperture ring (right). Most AF-S lenses that I know of do not have an aperture ring

Conclusion - "So, what kind of lens should I get?" 
There are plenty of misconceptions regarding AF vs AF-S lenses out there. Some people believe that AF lenses focus slowly. This is not accurate, as focus speed depends on individual lenses, whether AF or AF-S. I have used AF lenses that are as fast as their AF-S counterparts, especially with a pro-body. Another claim is that AF lenses are very noisy and distracting. Although they are noisier than AF-S lenses, each lens is different - not to mention, whether it is too noisy is purely a matter of subjective perception. I was never annoyed by the noise of an AF lens.

So, to the question "Should I get an AF or an AF-S lens", my answer is this: First of all, if you have a camera without a focus motor, then obviously you cannot autofocus with AF lenses, so the discussion stops there. If you do have a camera with a focus motor, then it is a matter of budget, really. In general terms, I would say that if there is an AF-S lens for what you need and you can afford it, prefer it. AF-S lenses are the future, and their benefits outweigh their disadvantages.

When to prefer an AF lens over an AF-S even when you can afford the latter? In individual cases, some AF-S lenses are, sadly, not as great as their older versions. Not, at least, in some aspects that might matter to you. One typical example is the Nikkor 50mm f/1.8 - I still use the AF version, because it has no discernible distortion, unlike its AF-S counterpart. Another reason to go for an AF lens is if you need the aperture ring. No aperture ring (like in the modern G-type AF-S lenses) means you can't use them with most extension rings and you can't use them with adapters on other systems - if e.g. you have a mirrorless micro 4/3 camera on which you want to use your Nikkor lenses.

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