Suffering from perpetually blurry images? The order in which you shoot may be having an impact. See why after the jump.

The Trick

The typical focus trick used by a lot of photographers is to always make use of the lens’s zoom capability - even if the final shot will be shot at a wider angle. To get a better focus, it makes sense to simply zoom in, depress the shutter halfway (typically) to lock focus, zoom out and recompose. That’s all there is too it. Intuitively, it seems that the camera’s auto focus system has a smaller area to hone in on, leading to more accurate results. It’s a common sense approach to solving a frustrating problem, but it doesn’t always work as advertised. In fact, sometimes it can actually hinder the focus.

The Caveat - Varifocal or Parfocal?

The success of the focusing trick depends on if your lens is varifocal or parfocal by design. A varifocal lens is designed so that the minimum focusing distance changes based on the length of the lens. A parfocal lens has a single minimum focal distance, regardless of the length of the lens itself.

Varifocal lenses are cheaper to design and comprise most consumer-level zooms on the market today. The problem with using the focusing trick with these lenses is that a focus shift occurs. What was once in focus when the lens was zoomed in is thrown back out of focus when you zoom back out. The trick doesn’t work as advertised.

Parifocal lenses don’t suffer from this type of problem, but a parfocal design is limited to the higher-end lenses on the market. There’s even some argument as to whether a true parfocal lens exists any more. For most hobbiest photographers, it’s a good idea to simply compose the image, focus and shoot. Leave the zoom method out of your bag of tricks.

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