Voigtlander Ultron 40mm f/2 SL II (Canon EF) - Review / Lab Test Report - Analysis
Lens Reviews - Canon EOS (Full Format)
Article Index
Introduction
Analysis

Distortion

The Ultron produces a moderate amount of barrel distortion on a full format camera (1.6%) which is usually not disturbing from a field usage perspective.

Vignetting

Full format DSLR are difficult partners when it comes to vignetting and the Ultron struggles here as well. The light falloff at max. aperture is quite hefty at around 2.3EV (f-stops) so unless you can live with the issue or are willing to post-correct it in an imaging applcation you should consider to stop down to at least f/2.8. There's no substantial light falloff anymore from f/4 onward.

MTF (resolution)

The resolution figures produced by the Voigtlander are pretty good although not superb. The center resolution is very sharp at f/2 and f/2.8 whereas the border/corner quality is only good. This isn't bad for sure - the lens is still very usable here. The center region receives quite a quality boost at f/4 but if you prefer to achieve a sharper border/corner region you should stop down to f/5.6 or f/8 - f/8 is also the global sweet spot of the lens. Diffraction has a limiting effect from f/11 onward.

The Ultron shows only a moderate amount of field curvature.

The centering quality of the tested sample was good.

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)

Chromatic aberrations (color shadows at harsh contrast transitions) are very well controlled at the image borders. This is actually a little surprising because we've seen slightly higher CAs in the APS-C so the issue does acutally improve a bit again in the outer image field.

Bokeh

The Ultron is a fairly fast lens so it's worth to have a look at its bokeh (the quality of the out-of-focus blur).

Out-of-focus highlights are pretty circular but at f/2 they have an "onion-like" inner structure which is certainly not pleasing. The aperture "disk" is already visible edgy from f/2.8 onward.

The background rendering is also relatively nervous whereas the foreground is smoother albeit still not perfect.

There are certainly better lenses regarding this specific aspect.

Verdict

The Voigtlander Ultron 40mm f/2 SL II is certainly a cute lens and such pancake lenses are generally "hip" at the moment. It does stop here though. Performance-wise it is a very decent lens. It may not be tack sharp at f/2 and f/2.8 but it's still a usable lens at these settings. The center quality is superb in the medium aperture range but if you want to achieve very sharp results across the frame you need to stop down to f/5.6 or f/8. Lateral CAs are very well controlled - this contributes to the subjective sharpness perception. The Ultron produces a moderate amount of barrel distortion. Light falloff can be a problem at f/2 but it's not extreme anymore at f/2.8 and not really an issue anymore beyond. The biggest problem of the lens is the rather rough quality of the bokeh (out-of-focus blur). This is a bit unfortunate because this is one of the primary playgrounds of such large aperture lenses. The build quality of the lens is exceptionally high and it is a joy to use it in field conditions despite or maybe because of the lack of AF. Regarding its small size and very low weight it is certainly a nice option if you want to travel with minimal gear.

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