Optical performance

Sharpness (Full-Frame)

Sharpness is outstanding. It's in a different league to the Canon MkI at low F/numbers, and this is the sharpest 35mm F1.4 currently available. It's also the joint-sharpest lens we've ever tested below 200mm – that is, aside from some of the uniquely special and very costly tele-primes that still hold a small advantage. The Canon MkII runs neck and neck with the mighty Zeiss Otus 55mm F1.4, and the highly regarded Sigma 35mm F1.4 Art also performs very well, but loses out on edge sharpness at F1.4.

What's really exceptional about the Canon 35mm F1.4 MkII is the image quality at maximum aperture, right across the frame, especially when mounted on a Canon 5DS R with 51mp sensor (with AA canceling filter). In the MTF-50 graphic above, the blue sea of high resolution extends all the way to the corners. There's much less need to stop-down for excellent sharpness as there is none of the slightly dreamy look at F1.4 often found with older designs. This is a revelation, and is characteristic of a new breed of premium quality fast primes that can now be used wide open without much compromise.

Stopping down improves fine detail usefully, as the blue in the MTF-50 graphic spreads out to mauve from around the center - the highest level on the chart. Sharpness in the center peaks at F2.8, with edge definition close behind and only a small dip towards the corners. The MTF-50 graphic shows edge sharpness improving to F4-5.6.

At higher F/numbers, sharpness reduces gradually in line with the inevitable impact of diffraction. The Canon 35mm F1.4 MkII is still delivering a very high standard of sharpness, but from mid-range and higher F/numbers, diffraction caps performance and holds it more in line with other high performance lenses. Most of the Canon MkII's sharpness advantage, and it is considerable, lies in the F1.4-4 aperture range.

Sharpness (APS-C)

Compared to full-frame, the higher resolution demands of the smaller APS-C format always push the levels down at MTF-50 (because it has to be enlarged more). On the other hand, APS-C sensors only use the sweet-spot around the centre of the image circle, so there's an upside.

The net result is reduced sharpness compared to full-frame - which is just the laws of physics at work - though the best quality lenses hold up relatively better on APS-C and the Canon 35mm F1.4 MkII is still well into the blue in the centre at F1.4, with only slight softening towards the edges. Sharpness improves incrementally to F4, peaking at a very high level. It's still the sharpest 35mm F1.4 you can buy, on either full-frame or APS-C formats.

Real-world sharpness

Canon 35mm F1.4 MkII and MkI versions compared, with and without aberrations corrections in ACR for distortion, vignetting, CA and LoCA. Canon 5DS R, ISO100, mirror lock-up.

The MkII's improved sharpness is clear, especially at F1.4 and towards the edges, and there's much better control of aberrations, with the exception of slightly worse vignetting at F1.4. The MkI is prone to purple fringing around bright areas and the MkII's BR Optics layer works well here. Correcting purple fringing in post processing is usually effective, though not always 100% successful when it's strong, occasionally throwing up artifacts - check the blue water bottle bottom-left with the MkI lens, where Lightroom has identified the fine red lettering as fringing and attempted to neutralise it.

Real-world aberrations

Chromatic aberration (CA) comes in different flavors and it looks like BR Optics may be contributing improvements to all of them, though Canon says it's particularly effective for Longitudinal CA (LoCA) (often known as purple and green fringing). This is commonly found in fast lenses, particularly at lower F/numbers, producing purple (or green) halos around bright highlights. Take a look at the real-world performance between the Mark I and Mark II lenses below.

Aberrations for inspection - the Canon 35mm F1.4 MkII vs MkI at F1.4, with and without aberrations corrections applied in Lightroom. Like all very low F/number lenses, vignetting is prominent and actually slightly stronger with the MkII. The MkI has mild barrel distortion, whereas the MkII has almost none. The MkII's sharpness advantage is clearly evident towards the corners (default sharpening applied), particularly around the sundial bottom-left, the plaque bottom-right, and along the towers. CA is most visible in these areas too, and also purple fringing with the MkI, though the MkII required no correction for this (BR Optics works). Apart from that, post-processing is identical in both images. Canon 5DS R, 1/400 sec at F1.4, ISO100, mirror lock-up. 

LoCA, usually seen as purple and green fringing on either side of the focus plane, tends to be prominent at wide apertures on fast primes. While it can be reduced in post-processing, it's tricky to remove completely, and although both green and purple fringing reduce in severity as the F/number is raised, they can linger on - as users of the Canon 35mm F1.4 MkI will testify. The effectiveness of BR Optics is convincing on both LoCA, and with the MkII version Canon moves from the bottom of the class to the top.

Lateral CA is the most recognizable form of CA, usually producing reddish/blue-green fringes, increasing towards the edges of the frame, and largely unaffected by aperture setting. Lateral CA is minimal with the Canon 35mm F1.4 MkII, and what little remains is easy to remove in post-processing.

Distortion is the curving of straight lines, particularly noticeable towards the edges of the frame with subjects like architecture, and does not change with aperture. The Canon 35mm F1.4 MkII is particularly well controlled, with only the slightest amount of barrel distortion - barely visible, and class leading. It's a big improvement over the MkI, though distortion is easy to correct in post-processing (albeit sometimes with a sharpness cost).

Fast lenses are invariably prone to vignetting - darkening towards the corners of the frame. It can be very noticeable at maximum aperture, but reduces quickly on stopping down. The Canon MkII recorded 2.3 stops darkening at F1.4, reducing to negligible at F2.8-4 which is very much on par for the spec, but perhaps surprisingly, it's actually slightly worse than the MkI, by about 0.3 stops at F1.4. Vignetting is easily corrected in post-processing, though many find the effect quite attractive.

Other optical characteristics

Flare

The Canon 35mm F1.4 MkII has high resistance to flare, improving on the MkI, and also beating any zoom of similar focal length. These comparisons show performance with and without aberrations corrections applied in Lightroom - for distortion, vignetting, CA and LoCA (purple and green fringing). Check the area around the sun to see how the MkII lens retains more detail of the branches before blowing out, and the almost total absence of flare spots. Almost all very fast lenses are prone to purple fringing as a result of axial CA, and the MkI is well known for it. In this severe test, it's very evident in the MkI images, while the MkII shows the benefit of Canon's BR Optics layer. Canon 5DS R, ISO100.

Flare can have a serious impact on image quality, when very bright light, e.g. the sun, is either in the image, or just outside it. A lens hood helps a lot with the latter (as well as providing good physical protection) but can do nothing when it's actually in the frame. All lenses suffer from flare to varying degrees, depending on the optical design, number of glass surfaces, efficiency of anti-reflection coatings and internal light traps.

There are various types of flare, including veiling glare (overall loss of contrast), spreading highlights, colored flare spots, and ghosting (mirror image of bright lights). Using any kind of filter, even the best quality, can make all these things worse, though sharpness is usually unaffected with shorter focal lengths.

The Canon 35mm F1.4 MkII performed exceptionally well in this difficult test, shooting straight into low afternoon sun - better than the MkI version, retaining more detail in the brightest area at all apertures, and showing much less of the purple fringing that is often problematic with the MkI. There was a notable absence of any flare spots. See examples in our widget above, and compare images with and without purple fringing corrected in Lightroom. 

We also tested some top-quality 24-70mm F2.8 zooms, at the same time, and they were not as good as either Canon prime for highlight spreading, while picking up some flare spots too, as a consequence of their more complex optical layout. Primes are generally a bit better at flare control.

Background blur

The ability to throw backgrounds out of focus at very low F/numbers, combined with high sharpness at maximum aperture, is one of the Canon 35mm F1.4 MkII's strongest suits. Background blur, commonly known as 'bokeh' (a Japanese word that roughly translates as 'fuzzy') is a complex characteristic that's hard to define and includes several factors, but shallow depth of field is probably the main one. The quality of bokeh can be subjective, though the hallmarks are smooth transitions from highlights to shadows, with clean out of focus highlights devoid of any onion-ring patterns and as close to circular as the aperture blades will allow. Here the Canon 35mm F1.4 MkII has nine rounded aperture blades for slightly smoother bokeh than the MkI's eight, though the most beneficial upside of that is the creation of 18-pointed stars from bright specula highlights, rather than eight. Bokeh circles appear to be cleaner and less devoid of rings and patterns as well, which mean more pleasing out-of-focus highlights.

Canon 35 F1.4L 1.4 2 2.8 4 5.6 8 11 16
Canon 35 F1.4L II 1.4 2 2.8 4 5.6 8 11 16
Sigma 35 F1.4 Art 1.4 2 2.8 4 5.6 8 11

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Focus shift

This is when the sharply focused plane moves at different apertures. It is often found in fast lenses that are prone to residual spherical aberration, meaning that after focusing on a certain point at maximum aperture as normal, after stopping down to the shooting aperture, the focus plane shifts backwards as spherical aberration is reduced. The effect is usually very slight and often passes unnoticed, but can sometimes catch you out at close distance when depth of field is very shallow. Given the Canon 35mm F1.4 MkII's high standard of overall aberrations correction, we weren't expecting any problems here - and so it proved, even at close range.