The function of certain focal lengths has changed with the introduction of the APS-C-sized digital sensor. A 30mm lens, once considered fairly wide, becomes equivalent to a standard 50mm view, while a 10mm or 12mm optic, once the place of a fisheye, becomes a standard wideangle.

Although cheaper, lighter lenses are now designed purely for these smaller sensors, professional lenses are still designed for full-frame use. It is rare, however, that both formats are considered, as it is difficult to satisfy both from one lens without overly inflating the cost or sacrificing the quality.

The Canon 8-15mm f/4L Fisheye USM, then, is unique in that, despite being a full-frame lens, the zoom range contains markings for APS-C and APS-H sensors, which correspond to the minimum focal length that can be used without vignetting.

Using this lens on a full-frame camera will provide a circular fisheye at its minimum and a full-frame wideangle image at its maximum, while on an APS-C or APS-H sensor it will produce a partial vignette at its widest point.

With this information it might be concluded that the lens is designed mainly for the full-frame user. After all, the L-series badging is usually for the realm of the professional or EOS 5D user. However, on an APS-C sensor this lens performs a similar function to a 12-24mm optic, which has always been a nice range for landscapes.

Features and build

The styling of this 8-15mm lens is in keeping with other L-series zooms, with the signature red ring around the barrel. The zoom ring sits at the back and offers a fairly free adjustment of less than a quarter of a turn. However, with both internal focusing and focal length adjustment, there is no need to worry about lens creep.

The manual focus ring sits at the front of the lens and is only very slim, as this lens is less likely to be operated in manual mode for the majority of users. The autofocus employs a ring ultrasonic motor (USM) for fast and quiet operation, and manual override always remains active should it be required. The focus window shows the small adjustment in focus point required for the widest 8mm focal length in red.

The front element is extremely concave and is protected by a removable lens hood, over which the lens cap attaches. Due to this large, domed front element there is no filter thread available, nor is there a rear filter slot, although with an APS-C sensor it is possible to cover the field of view with a standard square filter – if held in front of the lens.

The construction is fairly complex, comprising 14 elements in 11 groups including one aspherical and one ultra-low dispersion element. All elements are coated with Canon’s Super Spectra coating to reduce ghosting and flare, while the inside of the front element also features a subwavelength structure coating (SWC). The front and rear elements have a fluorine coating for water resistance.

At its 8mm setting, the lens offers an 180° field of view, although for APS-C and APS-H cameras this view is cropped, mostly in the vertical axis. The aperture maintains a constant f/4 maximum, which is more than adequate for a lens this wide, and with a minimum focus of just 15cm, a very shallow depth of field is achievable. As with most L-series optics, the mount includes a rubber ring to seal the unit against moisture and dust when attached to the camera body.

Handling

This lens is one of the most compact in the L-series range, and is shorter than even Canon’s EF-S 10-20mm wideangle model. Due to its size and field of view, stabilisation really isn’t missed in this model and the additional weight and cost would actually impair its handling and value.

When using the lens on an APS-C camera such as the EOS 7D, the limit switch – designed to stop the lens extending into a vignette – is useful as a guide, although I preferred to allow it to extend as required and crop the scene where necessary, as this allowed the full distortion effect to be achieved. The lens hood is handy for protecting the front optic and can remain on for APS-C use. However, when using the lens for its circular fisheye effect on a full-frame body, the front element becomes fully exposed, which does encourage the return of the lens cap between shots.

The autofocus is extremely rapid and left very few situations where manual control was necessary. With the minimum focus only slightly longer than the lens itself, it is possible for the subject to be almost touching the lens, although this can drastically reduce light levels as the lens starts to shade the subject, so careful metering is needed. Also, when dealing with more distant subjects, the huge field of view can skew the light levels so a centreweighted, or even spot, metering mode can be useful.

Image quality

A circular fisheye image is a very stylised effect and the lenses that create them rarely conform to regular optical demands. Distortion, for example, is a natural characteristic of a fisheye lens, so to mark a such an optic down for it would be counterproductive. This lens provides extreme barrel distortion throughout the range, and therefore the angle of the camera needs to be carefully observed if attempting a straight horizon. With an APS-C sensor, the distortion effects are less obvious and, at the maximum 15mm focal length, minimal correction is needed.

Aside from the areas of the frame that sit beyond the lens’s image circle, there is little light fall-off, creating a clean, circular fisheye with no sign of vignetting within the limited range on an APS-C sensor.

Our regular image chart was hard to capture with this lens due to the extremely wide view and the distance from the chart required. However, we have captured it at half size in the centre and in the corners of the frame to evaluative edge sharpness as well as maximum performance.

On a full-frame camera at 8mm for a completely circular fisheye, the sharpness appears impressive, resolving to an equivalent of 28 on our chart and remaining sharp right up to the edges of the circle. There is, however, significant signs of blue and magenta colour fringing towards the edges at all apertures. At the 15mm focal length, sharpness remains impressive, with a sweet spot of f/8 for optimum resolution, although edges still suffer from colour fringing. When mounted on the APS-C camera results were similar again, with slightly reduced signs of colour fringing around the edges but good overall sharpness, peaking at f/8.

For comparison, we took the same test-chart shots using the Sigma 8-16mm f/4.5-5.6 DC HSM, a digital-only lens that costs around £550. Designed as a wideangle rather than a fisheye, the Sigma offered a narrower but far less distorted view at 8mm and an almost distortion-free image at 16mm. However, sharpness at f/8 at the centre of the lens is almost identical to the Canon lens.

Image: Napoleon, taken at 15mm on an APS-C sensor

Image: Napoleon, taken at 8mm on an APS-C sensor (cropped to remove vignette)

The animals featured are homed at the Battersea Dogs and Cats Home and they, and many like them, are still looking for new owners. For more information, contact www.battersea.org.uk or 0207 622 3626

Distortion control

Many image-editing programs provide correction for lens distortion and these can often extend to extreme wideangles such as the 8-15mm optic. Panoramic software also tends to feature the ability to turn 360° circular images into regular framed scenes by a process known as unwrapping. However, as fisheye images are only 180° views, the process for converting them is not the same.

As the 8-15mm lens is still quite new it is not yet profiled in most software, so adjustments must be made manually. The controls will allow the removal of barrel distortion in the image, as well as control of colour fringing, although to return the circular shape to a standard rectangular frame it will be necessary to crop into the image.

DxO Optics Pro (www.dxo.com) is one of the most advanced lens-correction tools and, although it doesn’t currently have a dedicated profile for the 8-15mm lens within its controls, it has a fisheye option alongside barrel and pincushion correction to cope with the more extreme distortions at stake.

Images: Hayden, taken with the Sigma 8-16mm at 8mm on an APS-C sensor (cropped in). Hayden, taken at 8mm on a full-frame sensor for a full, circular fisheye effect

Image: Hayden, taken at 15mm on a full-frame sensor

The animals featured are homed at the Battersea Dogs and Cats Home and they, and many like them, are still looking for new owners. For more information, contact www.battersea.org.uk or 0207 622 3626

Resolution

We tested the Canon EF 8-15mm f/4L Fisheye USM on a Canon EOS-1Ds Mark III and an EOS 7D. An image was taken of our test chart with the lens set to each of its apertures, with the results shown below. Because of the extreme viewing angle of this lens, it wasn’t possible to fill the frame with the chart so the difference in size has been taken into account.

Our verdict

The Canon EF 8-15mm f/4L Fisheye USM remains a slight oddity and yet an extremely fun lens to use. The optical quality is impressive for such a wide lens and the performance is exceptional, from the autofocus to the weather-sealing.

For full-frame users, having the combination of a circular and full-frame fisheye in one optic will no doubt be appealing, although its use is limited by the subjects it will suit and the novelty of severe distortion can wear thin over time. APS-C users and, in some respects, APS-H users (EOS-1D range) are provided with a far less extreme effect and therefore a more widely usable lens.

The results still contain rather severe distortion, however, so remain suited to dynamic scenes and would need heavy lens correction for any landscape or architectural shooting.

Those seeking a controlled lens for APS-C should probably opt for the less expensive Sigma 8-16mm model, but those looking for extreme effects on both APS-C and, particularly, full-frame will really enjoy the possibilities this Canon lens has to offer.