SMC Pentax-DA 70mm f/2.4 Limited Lens Review

Features
Handling
Performance
Verdict
Specification



The Pentax lens repertoire seems to have its fair share of prime or single focal length lenses, bucking the trend towards the ubiquitous zoom. Many of these Pentax primes are described as Limited, not in the sense of them having a short production life, but rather in the limited number that can be made of these hand assembled, superior optics. The price is relatively high, so the questions are do these lenses indeed have superior finish and construction and are they of a higher optical standard? We shall now attempt to find the answers.

SMC Pentax-DA 70mm f/2.4 Limited: Features

The diminutive SMC Pentax-DA 70mm f/2.4 Limited weighs a very modest 130g, comprises 6 elements in 5 groups and has a 35mm-equivalent focal length of 107mm. This is very close to the traditional film 100/105mm lenses that are extremely popular as general short telephotos and portrait lenses. This 70mm lens, designed for the digital SLRs, is much more compact and machined out of aluminium to a very high standard.

A special extending lens hood, also in high grade aluminium, at first seems to be part of the lens but can be removed and 49mm screw filters can then be fitted. The lens design harks back to the M series days in that distance scales are viewed through a cut out. Depth of Field markings are also provided. The engraving of all the various markings is absolutely superb. The lens cap, again aluminium, is a generously deep push-on design that is lined with black plush velvet. There is no tendency for this to fall off.

There is no aperture ring on this lens, in common with most of the DSLR lens range. As befits a high end lens, a proper bayonet rear cap is provided rather than the push on transit type that comes with the kit lenses.

SMC Pentax-DA 70mm f/2.4 Limited: Handling

We have here a beautiful jewel of a lens, with clearly very superior finish and construction. In terms of handling, it fits cleanly and firmly onto the camera body and is instantly ready for use after the push on cap is removed. The built in extending lens hood is, as mentioned, detachable, but for most purposes can be considered an integral part of the lens.

Focusing is smooth and fast on the K-5 and the added advantage of Quick Shift is available. After AF has locked on, the focusing ring can be adjusted to tweak the final focus position. In this test, this never proved to be necessary but it can be a very useful feature. Manual focus is nicely damped and although a different feel to the classic manual focus lenses it is functionally perfectly satisfactory.

The 70mm focal length is perfect for portraits and during this test I was able to try this out extensively on a couple of photoshoots. This is always a personal choice, but when using film I preffered to use 100mm lenses, so this is as close to the same thing as it gets.

Short telephoto lenses are also very useful for picking out details in general photography and, coupled with such a compact size, this may well be an outstanding lens for general travel.

Those who enjoy fine engineering will also appreciate this lens, but it takes pictures as well and its handling is spot on.

SMC Pentax-DA 70mm f/2.4 Limited: Performance

Looking at the technical charts, it's clear that Pentax have made the decision to heavily correct for chromatic aberrations across most of the field, but allow the corners to drift a little. In the centre, CA is almost banished, as we move out into midfield the control is still excellent. The corners are quite demanding and although CA is visible it is only so in extreme conditions. In practice, CA will not be a problem.

With such a compact design, I had expected that there would be significant pincushion distortion, but the smaller sensor size does seem to have made lens design easier here. In fact there is indeed pincushion distortion, as with most strong telephoto designs, but it is fairly minimal and in general use not apparent. A better than expected result.

Flare, in common with other Pentax lenses I have tested, is very well controlled and almost impossible to induce. The effective pull out hood helps here as well as the SMC coating.

		The MTF50 graph looks at the fine resolution and ability to record a very high standard of detail. When MTF measurements started to be used in the 1970s many magazines started off using MTF40 data and quickly reduced that to MTF30 as the figures always looked low. This goes to demonstrate how much more resolution we have for our DSLR lenses. MTF50 is a very high standard and this 70mm lens shows a very good but not exceptional performance in this respect. The resolution is well maintained across the field and there is a very clear peak at f8. This classic rise and fall pattern is the hallmark of a good lens.
		The MTF20 graph shows us information about the overall contrast or “bite” of a lens, and the 70mm is a typically Japanese design of the sort that caught the imagination of photographers after they discovered Nikon rangefinders in the 1950s. Rather than high resolution, low contrast lenses such as the German lens makers produced, we had very high contrast lenses with bite that have lower fine resolution. There is no free lunch in lens making. Here Pentax have opted for plenty of bite and at f8 the performance in this respect is superb.

Of course, in the end, these measurements give us clues as to how a lens will perform, but it is the practical result that is most important. The 70mm delivers a very high standard of performance and produces very clean, sharp and contrasty images with a minimum of distortion, flare or CA.

An unusual colour is recorded faithfully, ISO200, 1/50, f/11, 70mm (35mm equiv: 105mm)		A total lack of flare gives deep rich colour in this late evening shot, ISO200, 1/500, f/8, 70mm (35mm equiv: 105mm)
Details can be captured from a reasonable distance, thus reducing distortion, ISO200, 1/640, f/8, 70mm (35mm equiv: 105mm)		In the studio, the lens allows a reasonable working distance. This improves communication with the model and ensures flattering perspective, ISO200, 1/160, f/11, 70mm (35mm equiv: 105mm)
A grab shot in a high contrast situation. The lens focused swiftly and locked on with no problem, ISO1600, 1/200, f/4, 70mm (35mm equiv: 105mm)		Another spontaneous shot and there was no problem with catching the moment, ISO1600, 1/60, f/3.5, 70mm (35mm equiv: 105mm)
Difficult colours are handled well, ISO200, 1/30, f/8, 70mm (35mm equiv: 105mm)		Subject shapes are accurately recorded, ISO200, 1/200, f/8, 70mm (35mm equiv: 105mm)
CA is well controlled over most of the field, ISO200, 1/1000, f/8, 70mm (35mm equiv: 105mm)		70mm on digital is an ideal focal length for portraits, ISO200, 1/100, f/4.5, 70mm (35mm equiv: 105mm)

SMC Pentax-DA 70mm f/2.4 Limited: Verdict

Sometimes when reviewing a lens it's just so hard to actually hand it back after the job is done and this is one of those lenses. It's a superb piece of engineering and has optical qualities that are balanced to just my taste. It is not a macro lens, so very close shots are not possible, but it is ideal for medium range applications and especially portraiture. Highly recommended.

A compact, superbly built lens with real optical bite makes an ideal short telephoto for Pentax users.

SMC Pentax-DA 70mm f/2.4 Limited: Pros

High quality of construction
Compact
High optical quality
Excellent handling

SMC Pentax-DA 70mm f/2.4 Limited: Cons

Price

FEATURES
HANDLING
PERFORMANCE
VALUE FOR MONEY
OVERALL

SMC Pentax-DA 70mm f/2.4 Limited: Specification

Focal Length	70mm
Equivalent to 35mm format	105mm
Maximum aperture	f/2.4
Minimum aperture	f/22
Angle of View	68 degrees
Construction	6 elements / 5 groups
Focusing Range	0.7m - infinity
Magnification	0.12x Max
Filter size	49mm
Mount	Pentax K-AF
Weight	130g
Dimensions (Length x Diameter)	26 x 63mm
Kit Content	Front cap Rear cap Soft case
Special Features	Quick Shift focusing Super Protect coating