Camera Accessories

The two large-diameter, glass-moulded aspherical elements correct aberrations like curvature of field and distortion, both common in wide-angle lenses. In addition, two UD elements are used to minimise chromatic aberrations. Rear focusing with floating elements has been carried over into the new lens, along with an ultrasonic motor (USM), which supports fast and quiet autofocusing with full-time manual override.

The front element is non-rotating, allowing use of angle-critical attachments, such as polarisers and graduates. Like its predecessor, stabilisation is not provided. The new lens is 100 grams heavier than its predecessor and is made from lead-free glass in compliance with the European Union's Restriction of Hazardous Substances Directive (RoHS). It also features a newly-designed anti-reflective SWC (Subwavelength Structure Coating) technology.
Developed specifically for Canon's optics, this coating minimises flare and ghosting by aligning an array of nano-scale wedge-shaped structures smaller than the wavelength of visible light across the surface of the lens. The wedges continuously change the refractive index of light at the glass-air boundary, dramatically reducing reflections.


The above diagram shows how Canon's Sub Wavelength Coating subdues reflections at glass/air boundaries. (Source: Canon.)

Conventional anti-reflection coatings work by providing two light-reflecting surfaces, one at the glass/coating boundary and the other at the boundary between the coating and the air. This system is effective for relatively flat surfaces but not with highly-curved surfaces (such as those found in fast wide-angle lenses).  Here, high angles of incidence of the light can prevent reflections from being cancelled out. 

The new SWC system enables the thickness of the coating to be controlled progressively so that the wedges are always positioned at angles equivalent to a quarter of a wavelength. This ensures reflections off the glass/coating boundary are out of phase with light reflected from the coating/air boundary, effectively cancelling them out. Because Canon's SWC coating allows the effective thickness of the coating to be varied with the curvature of the lens, the system can be used with very wide-angle lenses.

Whereas Canon's earlier 24mm f/1.4 lens had seven diaphragm blades, the new lens has eight and they close to a circular aperture for attractive out-of-focus blurring. Both lenses accept the same 77mm diameter filters. 

Build and Handling
The EF 24mm f/1.4L II USM lens is built to professional standards and equipped with Canon's advanced weather and dust sealing making it ideal for all kinds of outdoor photographers, but particularly photojournalists and landscape photographers. Although heavier than its predecessor, it is relatively compact and a comfortable match with both the EOS 5D and EOS 40D bodies we used for our tests. The overall design gave the lens a nice balance, despite its weight, and the focusing ring was easy to reach and moved silently and very smoothly.

The metal mounting plate is accurately machined and easy to fit on the camera bodies, where it locks in securely. The lens barrel is made from metal and high-grade polycarbonate. It's solidly constructed and coated with a smart semi-matte black.  The overall appearance of the new lens is similar to its predecessor, with a narrow red ring (identifying it as an L-series model) towards the front and a 1.8 cm wide ridged focusing ring a little further back towards the mount.

Behind the focusing ring on the main barrel is a distance scale with distances in feet and metres, ranging from 0.25 metres to infinity. Associated with it is a depth of field scale engraved on the lens barrel, covering apertures from f/4 to f/22. Behind these scales and lower down on the left side of the main barrel is an AF/MF switch.

The large f/1.4 maximum aperture provides bright viewing for low-light photography and is ideal for differential focusing. Canon claims this lens is the brightest large-diameter f/1.4 high-performance wide-angle L lens in the 24mm class. The new lens is also compatible with Canon's E-TTL II flash system and has electronic contacts that provide distance information to current lenses.

Supplied accessories include the EW-83K lens hood (which is flock lined to suppress reflections), the E-77U lens cap and end cap and the LP1319 soft lens case. 

Performance
To illustrate some of the reasons for preferring a (significantly) more expensive prime lens over a zoom lens, we have run some parallel tests with the EF 24mm f/1.4L II USM and EF 24-105mm f/4L IS USM lenses, the latter set at 24mm.  For these tests we used a Canon EOS 5D body. Our tests covered both Imatest analysis and shots showing areas in which the lenses exhibited noticeably differing performance.

In Photo Review's Imatest tests, the prime lens delivered consistently higher resolution than the zoom lens in our Imatest tests, particularly at wider aperture settings. Edge sharpness was also measurably superior in the prime lens, although the difference between the two lenses closed as the lenses were stopped down.

Best performance for the prime lens was between f/4 and f/8, while the zoom peaked at f/6.3 but delivered relatively high resolution from f/4.0 to f/9.0. The performance of both lenses tailed off from f/8 on and the differences between them increased from about f/11.  The graph below shows the results of our Imatest tests covering apertures from f/4 to f/22.

Unfortunately, at wider aperture settings, the resolution of the EF 24mm f/1.4L II USM lens was disappointing, although by f/2.8 it had matched the centre resolution of the zoom lens at f/4. However, edge sharpness was no better than the zoom lens right up to f/6.3, although it improved rapidly thereafter. The graph below shows the results of our Imatest tests on the EF 24mm f/1.4L II USM lens across its full aperture range.

Lateral chromatic aberration was consistently low throughout the aperture range of both lenses with the EF 24mm f/1.4L II USM lens, remaining consistently within the negligible category except at apertures between f/1.4 and f/2.0. However, the difference between the results wasn't as great as we expected and the 24-105mm lens only crept into the 'low' category between f/4.0 and f/5.0 and f/18 and f/22. The graph below shows the results of our Imatest tests.


The blue line marks the boundary between 'insignificant' lateral chromatic aberration and 'low' lateral CA.

As a walk-around lens, the test lens was both a pleasure to use and surprisingly versatile for a prime lens. Despite its edge softness, it delivered outstanding results in very low light levels, where we were able to use shutter speeds as slow as 1/4 second with the EOS 5D. The wide aperture also provided a bright enough image to support manual focusing after dark. In bright conditions, flare and ghosting were negligible as long as the lens hood was kept in place.

Vignetting was obvious at the widest apertures but gone by f/4. Rectilinear distortion was negligible, compared with the EF 24-105mm f/4L IS USM lens, which also produced noticeable vignetting at apertures up to f/8. Sample images showing shots taken with each lenses at f/4 and the prime lens at f/1.4 are provided below.
 Close-up capabilities of the test lens are fairly limited, due to a minimum focusing distance of 25 cm. However, bokeh at wide aperture settings was smooth and attractive and the wide angle of view provided some interesting perspectives on subjects.

Despite its relatively high price tag, Canon's EF 24mm f/1.4L II USM lens will be attractive to wedding and landscape photographers, although for widely different reasons. The former will appreciate its superb performance for available light photography in low light conditions. They won't be fazed by vignetting and edge softening at wide apertures - which may even be seen as advantages.

Landscape photographers will love its rugged build and relatively light weight and compact size. They will also enjoy its superb performance at mid-range and small apertures.  Photojournalists may be the main class of photographers who will buy this lens since they will revel in all these advantages. All types of photographers will appreciate the easy compatibility of this lens with the 5D series bodies.

Buy this lens if:
- You have one of Canon's 'full frame' camera bodies.
- You want a fast lens for available light photography and require high centre-of-field performance across the aperture range.
- You need a wide-angle lens that can handle occasional mists, spray and light showers.
- You require distortion-free images.

Don't buy this lens if:
- You're using a body with an APS-C sized sensor (the 1.6x crop factor will limit the wide-angle coverage).
- You take most low-light shots with flash.
- You really need a zoom lens.
- You shoot lots of close-ups.

IMATEST GRAPHS

SAMPLE IMAGES

 
The test lens at f/1.4; ISO 200, 1/1000 second shutter speed; full image frame. (Note the vignetting at the wide aperture.)

Corner crop from the above image.

Centre crop from the above image.

The test lens at f/4; ISO 200, 1/125 second shutter speed; full image frame. (Note the reduction in vignetting.)

Canon's 24-105mm zoom lens at 24mm; ISO 200, 1/100 second at f/4. (Note the vignetting at the wide aperture.)

Corner crop from the above image. (Both distortion and edge softening are visible.)

Centre crop from the above image.

Close-up; 1/3200 second at f/1.4. (Note the smooth bokeh.)

Close-up; 1/50 second at f/16.

Close-up; 1/160 second at f/1.4.

ISO 400, 1/2 second at f/1.4.

ISO 500, 1/10 second at f/1.4.

ISO 500, 0.6 second at f/4.

ISO 500, 1/60 second at f/4.

ISO 400, 1/8 second at f/1.4.

ISO 200, 1/13 second at f/1.4.

ISO 400, 1/4 second at f/4.