SMC Pentax-DA 55-300mm f/4-5.8 ED

SMC Pentax-DA 55-300mm f/4-5.8 ED: Performance

In practical picture taking there is no doubt that this lens produces sharp, excellent quality images, with outstanding colour reproduction.

Looking at the test charts the usual patterns of performance for a zoom of this type are evident. The best performance is found at shorter focal lengths and in the centre of the field, where the levels of correction are concentrated and very impressive. At longer focal lengths the resolution does drop, especially at the extreme corners, but, to be fair, this is not where the main subject usually is and it is quite a demanding set of tests.

Taking distortion first, we find mild barrel distortion at 55mm that soon changes to pincushion for the rest of the range. This is well controlled for such a compact design and should not impact on the types of photography the lens is aimed at.

Chromatic aberration is likewise well controlled, extremely well at the centre of the frame. Part way across this holds, but at the corners there is much more evidence of CA. However, it is still within a reasonable limit and should only become intrusive at the edges and in challenging circumstances. An example might be the branches of a tree against bright sky.

	CA	MTF20	MTF50
55mm
100mm
200mm
300mm

Fine detail resolution is indicated by the MTF50 charts, a very demanding standard. The lens is commendable for its uniformity of performance across the frame. Detail is well resolved but definitely better at shorter focal lengths.

The visual quality of the lens is enhanced by its good overall contrast, and this shows clearly in the MTF20 charts. This is ideal for wildlife and the lens produces punchy, sharp pictures with no problem. Again, uniformity across the frame is impressive.

This shot shows superb colour reproduction and fine detail, ISO800, 1/1250, f/8, 300mm (35mm equiv: 450mm)		Combined with the fast AF of the K-5 wildlife photography is well within range of this zoom lens, ISO800, 1/200, f/8, 300mm (35mm equiv: 450mm)
Aided by the use of a tripod, the sharpness is impressive, ISO200, 1/13, f/8, 230mm (35mm equiv: 345mm)		Long lenses are not only for isolating detail and full use can be made of the available depth of field, ISO200, 1/15, f/22, 98mm (35mm equiv: 147mm)

Likewise, pictures of small flowers are perfectly balanced against out of focus backgrounds and the long focal length means that specimens at the back of wide garden borders can be captured easily.

In summary, the lens shows a commendably uniform and very satisfactory performance and is suitable for a wide variety of applications.

70mm was selected as a flattering focal length for portraits, ISO200, 1/50, f/8, 70mm (35mm equiv: 105mm)		The lens is also a good choice for larger groups of fungi, ISO200, 1/8, f/16, 210mm (35mm equiv: 315mm)
The reach of the lens is ideal for isolating single blooms, even if they are at the back of wide flower beds, ISO200, 1/40, f/16, 150mm (35mm equiv: 225mm)		This feather, shot at the minimum focus distance, is full of detail, ISO200, 1/25, f/16, 170mm (35mm equiv: 255mm)

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