Canon RF 85mm f/1.2 USM L - Review / Test Report - Analysis
Lens Reviews - Canon EOS (Full Format)

Distortion

Image auto-correction is a convenient way to hide design issues but Canon obviously thought not to bother with this. The original distortion characteristic of the Canon RF 85mm f/1.2 USM L is just ... perfect.

Vignetting

A similar degree of perfection can't really be achieved when it comes to vignetting - physics has its limits here. The front diameter of the RF 85mm f/1.2 USM L is pretty huge but this can't prevent a light falloff of 2.2EV (f-stops) at f/1.2. However, in the grand scheme of things, this is still relatively moderate for such a lens. The issue is greatly reduced at f/2 and mostly gone from f/4 in real-life terms.

If you choose to activate image auto-correction either in-camera or your favorite RAW converter, the vignetting is just noticeable at f/1.2 in very critical scenes. Please note that auto-correction will increase image noise in the image corners due to signal amplification.

MTF (resolution) at 30 megapixels

Coming back to perfection - the resolution. It's breathtaking really and that's not just at medium aperture settings but also at f/1.2. The center quality is already excellent and the outer image field is easily on a very good level. Stopping down increases the quality slightly from great to stellar. Pure lens porn ...

The centering quality of the tested sample was very good. The field curvature is negligible.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Lateral CAs have an average width around 0.3px at the image borders. This is negligible. So it seems as if Canon's new BR element did its job here.

Bokeh

The following discussion of the bokeh of this lens is probably like questioning the existence of a god for some owners ...

If bokeh just means a shallow depth-of-field combined with a maximum of foreground/background blur in your book - read no further because then this is about the most perfect lens in this respect that you can get.

If you think that there's a little bit more to the topic, you may wish to read further. Let's start with a sample of the worst-case scenario:

Is that a good bokeh? Of course, the worst-case scenario is just that - the worst case.

Anyway, let's not get ahead of ourselves here and continue with the rendering of out-of-focus highlights. They are, generally, nice with just a faint onion-like sub-structure and no outlining. The highlight discs are perfectly circular between f/1.2 and f/2 and there's only a hint of a more edgy aperture shape at f/2.8.

When broadening our view to the whole image frame, the situation is, of course, a little different. The shape of the highlights deteriorates towards the corners. Despite the huge lens barrel, this happens fairly early but this does, of course, also related to the extreme aperture. The "good" center area broadens quite a bit at f/1.6 although the corner highlights look less pleasant than at f/1.2 here. The corner highlights are almost restored at f/2 and basically circular at f/2.8. But then who wants to shoot at f/2.8 with this lens. Please note that the irregular shape in the corners is absolutely normal - it's a mechanical vignetting effect.

As far as the general blur is concerned, there are two stories. The sample crop to the right below shows the bokeh in the foreground. It is smooth and buttery. The background blur - shown to the left - is more complex. You may notice that the "crown" is actually fairly harshly rendered. Overall this is far from being bad but hard contrasts can be a bit of an issue as shown in the sample image at the beginning of this section.

Bokeh Fringing

In a perfect world scenario, you won’t see any axial CAs thus color fringing on the Z-axis. However, only a handful of fast lenses are correcting the issue effectively. The Canon RF 85mm f/1.2 USM L is very good in suppressing this but it's not fully corrected. At f/1.2 you should be able to spot the usual purplish color fringing in front of the focus point and a greenish halo beyond. However, the fringing is greatly reduced at f/1.6 and pretty much gone at f/2. As such it is better than the vast majority of fast 85mm lenses.

The focus point does only insignificantly shift to the rear when stopping down.