Lens review

Pentax smc DA 50 mm f/1.8

22 December 2012
Arkadiusz Olech

10. Autofocus

When it comes to the speed of the focusing mechanism we have no reservations whatsoever. Taking into account the fact that the working range of the ring is wide, the speed reaching 0.6-0.7 of a second should be deemed very good.

However here ends the praise. The autofocus is very noisy – it is a typical whining ‘drill’, a mechanism which currently most of the producers shun. What’s more, the focusing mechanism of this lens should be rather called a ‘missing mechanism’. It doesn’t matter whether it is light or dark, whether you work with older or newer firmware, outside during the day or inside, with artificial bulbs, there are situations in which half of photos are misfocused. It is really a dreadful result – so dreadful that shooting photos of test charts I gave up working in the AF mode (usually I take the same number of photos in both modes, automatic and manual) and treated this lens as a completely manual instrument. Fortunately the manual focus ring, working as it should, made it completely possible.

To check how the lens performs on other bodies we decided to attach it to the elderly Pentax K10D. Unfortunately in that case the back focus was so significant that also working in the AF mode was impossible.

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It was difficult to determine any concrete tendency among misses the lens provided while working on the K-5; the same amount seemed to feature examples of front and back focus.

What’s more, that photo shows clearly that when you move from the centre to the edge the sharpness level decreases swiftly. The centre is still more or less sharp but it’s enough to move sideways to find out that the image becomes completely useless.

Pentax smc DA 50 mm f/1.8 - Autofocus