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Tokina 11-16mm f/2.8 SD (IF) DX

TOKINA lenses – the brand name for optical giant Hoya’s interchangeable range – have always been renowned for their tank-like build quality and resistance to plastic trends. They compare so well with Nikon’s own lenses it is hard to tell the difference by feel, and the current design also matches Nikon more than it does Canon.

The latest news is that Tokina is to introduce the 11-16mm ƒ2.8 in Sony Alpha mount. Tokina stopped making Minolta mount lenses shortly before their parent company Hoya acquired Pentax. On October 28th 2010, Kenro UK announced availability. B&H has the lens in Sony fit here. The Tokina factory has been producing Pentax lenses (not all of them) and also the Schneider-Kreuznach branded range for the Samsung GX Pentax clone DSLR system.

Now that Samsung has gone its own way with the N-system, abandoning Sony sensors and Pentax lenses, some of the conflicts which possibly inhibited Tokina from returning to the Alpha mount have disappeared – and some of the capacity and market share taken up by their Samsung contract likewise. Alpha lenses will fill the gap nicely.

Sony must, surely, have observed that the Tokina 11-16mm ƒ2.8 is not just the best such wide-angle currently made. It’s also the only one which activates the ƒ2.8 central double cross sensor of the Alpha 700 properly, doubling the focus accuracy which is critical with such short lenses. Depth of field may be huge, but depth of focus (the tolerance at the sensor plane) is not. Calibration needs to be perfect with lenses like this. The 11-16mm could be a perfect match for the next generation of Sony 700-level camera with one or more ƒ2.8-capable AF focus points… should such APS-C models ever be made, and the SLT ‘translucent’ generation not take over entirely.

Tokina has made lenses for the Alpha system in the past. They designed, and produced exclusively for Minolta, the 100-400mm ƒ4.5-6.3 APO AF lens. They made one variant of the 28-80mm ƒ3.5-5.6 kit lens, regarded as the best optically. It is possible that Tokina also designed the 100-300mm ƒ4.5-5.6 APO (D) and one or more of its predecessors, whether delivered to Minolta in element form for assembly or not. I would also suspect that odd and much acclaimed one-off, the 35-200mm ƒ4.5-5.6 Xi Power Zoom, of origins outside Minolta. Tokina would be the most likely source.

So it is not out of the question that Hoya/Tokina is once again involved in working with the Alpha system, this time with new owners Sony. But the released 11-16mm for Sony says otherwise. It has a screw drive focus, not SAM or SSM type, despite the Nikon version using motorised focus to ensure compatibility with all models. It has only five contacts on the mount, meaning that it is not ADI compatible (D series) and does not pass the full range of lens data to the camera. In fact the chipset must be very similar to that on much older Tokina designs before they stopped making Minolta AF fit.

I was able to test the Tokina 11-16mm on a Nikon D90 (same basic sensor as the A700, A500 in terms of resolution and physical size) thanks to professional photographer David Bryce, during a seminar held in Scotland in Autumn 2008.

The brief test

David Bryce was one of the first to obtain a Tokina 11-16mm ƒ2.8 zoom, and I had a chance to take a good look at it during a Master Photographers Association Scottish Region seminar in 2008. In addition to trying it out on the Nikon D90 with architectural subjects (the venue, Solsgirth House) I was able to make some full aperture and ƒ4 tests of no pictorial merit, positioning details in the corners to check out how well it performs. If you click on most of the images, you will be able to access full size 12 megapixel files.

Here’s the subject – using converging verticals and a very close viewpoint, at f/9 and 11mm, in nice sunny conditions. The sun kindly disappeared for the straight-on tests of wide open and f/4 performance.

11mm at f/2.8

16mm at f/2.8

11mm at f/4

16mm at f/4

There was some sign of softness in the corners which was not fully removed even by ƒ11. What was surprising was the relative lack of vignetting – even at ƒ2.8, the corners were well illuminated. Performance on Canon’s 1.6X sensor (substantially smaller than the Nikon 1.5X sensor) will appear a little better as the extreme corners are not included.

Uncorrected at 11mm (click image for a larger, but not full size, view)

Corrected in Photoshop (Distortion>Lens Correction) with 3% de-barrelling

The lens turns out to have very good flare resistance, and better geometry than might be expected, needing only 3% correction for pure barrel distortion at 11mm. On most distant subjects, or buildings photographed to allow convergence rather than correct the verticals no correction is really needed.

Compared to Nikon’s 18-105mm VR lens, the Tokina had higher contrast and produced a more punchy image. Both lenses at their widest needed a similar CA correction in Adobe Camera Raw of around -30 Red/Cyan defringeing, and the Nikon showed more vignetting. On revisiting the files, I found the Tokina could survive with -20 CA correction and was generally cleaner than the 18-105mm. I’ve since bought an 18-105mm VR Nikkor myself and can confirm it’s a modest performer optically, but cheap.

16mm at minimum focus, f/8, into the light with a very bright sky

Close focus was impressive, more useful at 16mm than 11mm, with not too much field curvature or corner sharpness loss. The close-focus shot also shows pretty good bokeh, and being taken directly into the light, well controlled internal reflections with no veiling glare over the shadows.

For most medium and long distance subjects, full aperture would not produce an acceptable print. The 35mm shaped frame would need to be cropped to 10 x 8 shape to lose unsharp zones at the ends of the shot. The centre, even wide open, is exceptionally sharp. At ƒ4 there is a small improvement but not enough to make the full frame useful.

Interior at f/8, 1/30th. The Nikon D90 has no sensor stabilisation and the Tokina also has no IS/VR. You can see the degree of barrel distortion present at the frame end (the example above shows it on the long side, this displays it on the short side. The good news is that although it is strong barrel, it is simple, not moustache-shaped wave form distortion. This means a simple correction can fix it, no need for a lens geometry map.

By ƒ8 sharpness is good across the frame bar the extreme corners; these may demand ƒ11, an aperture which now begins the soften the whole frame as a result of diffraction. Even so, for architectural or industrial shots, ƒ11 would be a suggested setting to get corner to corner sharpness at 11mm. With the right subject and precise focusing, wider apertures may produce perfect results, as the very ordinary shot below shows.

Normally, I either wouldn’t put up an image with a badly angled composition and poor lighting like the one above – at the least it would be cropped and straightened. However, this particular shot at f/7.1 and 11mm must have been optimally focused (I’d guess, on the gravel not the house) and shows what the Tokina can do when the depth of field is adequate. The grass is sharp pretty much to the extreme corner. Click to view the full size file.

The centre to edge difference at full aperture is emphasised by the unusually high resolution on-axis. The ƒ2.8 aperture enables extra accurate focusing with most DSLRs including the D90, and this really pays off in terms of micro-contrast and detail.

We do not yet know how Sony will tackle the problem of ensuring accurate Phase Decect AF with new higher resolution values. It is a more complex subject than I thought possible, with everything from the focal length and aperture to the design parameters of each lens affecting accuracy. AF point (front or back focus) even changes with temperature, more so for outer field sensors than the central point. The Canon 1D MkIV has a temperature sensor in its AF module to apply recalibration on the fly and correct for the differential expansion of silicon and glass components of the AF array within its working temperature range.

There is one surefire way to get perfect wide angle focus – contrast detect focusing from the imaging sensor itself as found on the Alpha 33 and 55 in video mode, or for more conventional Alpha system owners (so far), Manual Focus Check Live View on the Alpha 580, 560, 550 and 500. The Tokina 11-16mm will be perfect for this method as the wide aperture will show the correct focus point clearly.

The 15-point AF sensor in the SLT models 55 and 33 has three cross-sensors, but all are ƒ5.6 sensitive just like all of Nikon’s sensors from entry level to D3X. Nikon has never gone down the ƒ2.8 sensor route used by Canon and Sony. My tests of the Sigma 8-16mm on the Alpha 55 indicate that with wide-angles, the phase detect is just as vague as ever – capable of locking confirmed focus over a huge distance range.

The Tokina seems to be a lens suited perfectly to one body only for Phase Detect AF – the Alpha 700. And there is no guarantee such a camera will ever again be made by Sony.

B&H has the lens in Sony fit at $599 when last checked

– David Kilpatrick


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