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- 50 mm Bokeh Contest -

Review Versioning:

• 29.5.2010: Initial upload

From left to right: Sigma 50 mm f1.4 EX DG HSM, Nikkor AFS 50 mm f1.4 G, Nikkor AIS 50 mm f1.2, Nikkor AIS 50 mm f1.8

The 50 mm lens has been a popular choice for portraits with APS-C sensor cameras and for low light photography in general. For Nikon based photographers the AF-D version of the 50/1.4 was long overdue for an update when Nikon introduced the AF-S G type version with a fresh and new lens design.
Lets summarize: mapping the market for a 50 mm for a while the only AF alternatives for the Nikon F-mount right now are:

1. the new Nikkor 50 mm AFS f1.4G,
2. the old D-type Nikkor 50 mm AF 1.4D,
3. the D-type Nikkor 50 mm AF f1.8D and
4. the Sigma AF 50 mm f1.4 EX DG HSM.

For manual focus lenses there are more alternatives around. Usually with these low light and minimal DOF lenses you do want an AF option. But if that's not the case - here are some other candidates:

Of the 4 AF lenses 2 have an ultrasonic ring engine for focusing. So lets concentrate on these two concepts. The Sigma 50 f1.4 EX DG HSM and the Nikon AFS 50 mm f1.4G are the most recent developments. There are rumours floating around of a new Nikon f1.2 AFS version to be released soon (might never happen - but who knows).

Sigma did put some effort into redesigning the 50 mm so it will be interesting to see how the Sigma compares to the Nikon. This lens comparison will primarily focus on some often not described characteristics of these lenses: out of focus properties or often labelled "bokeh" characteristics. There are some other important aspects to consider when one decides which lens to buy. Sharpness and focus accuracy comes to mind. But my primarily concern was how the out of focus areas look like in these lens designs. The Sigma received lots of praise for its bokeh in various comments and net reviews - so this lens seems to be a clear option for portraits, weddings and child photography.

The Sigma is a huge lens compared with the usual lens size in this class. The front element is close in size to the Nikon 85 f1.4 AF-D but the hefty feeling of this lens makes the lens/camera combo just feel right - especially with larger Nikon DSLR bodies the Sigma seems to be just right in size and weight. And that should be mentioned: the lens just looks somehow good with this massive amount of glass (was just wondering why I hesitate to name it: the lens looks sexy! here we go). The lens comes with the typical Sigma surface finish. This crinkle paint seems to attract dust and dirt but the grip with this lens is perfect.

The AF with my Sigma sample was constantly back focusing on close and far range objects (could be corrected with a focus calibration enabled camera body). The Nikon sample that I used is doing much better here. AF is nearly always spot on - but the Nikon AF is much slower than the Sigma HSM AF system. If you need a fast AF than the Nikkor is not the lens for you. The AF just doesn't "snap" to its focus point and seems slow and sluggish. The Sigma is more responsive here and the quick lock on objects makes fun. The Sigma seems however to miss the precise focus point more often.  

Resolution figures are not my main concern with these lenses. If you want to know more about MFT etc. than check the DPReview pages about both lenses:

DPReview Nikkor 50 mm AFS G f1.4
DPReview Sigma 50 mm DG HSM f1.4.

One aspect that is rarely tested is the quality of the OoF highlights and the quality of the bokeh of these two lenses. This is a property that is difficult to measure and also subjective.
The Sigma has a very two-sided character here. It renders the out of focus objects with better (smoother) bokeh than the Nikkor - the style has a painting like finish - but this is only true as long as your out of focus area has no strong highlights.

Top: Nikon AFS 50 mm f1.4G, below: Sigma AF 50 mm f1.4 EX DG HSM, both lenses @ f1.4

Top: Nikon AFS 50 mm f1.4G,  below: Sigma AF 50 mm f1.4 EX DG HSM, both lenses @ f1.4

Nikon AFS 50 mm f1.4 G

Sigma AF 50 mm f1.4 EX DG HSM, both lenses @ f1.4

With the Sigma the out of focus highlights come with a strange concentric ring shape structure that seems to originate from the aspheric lens element design. The aspheric lens element is not precisely polished in all direction because the lens radius changes all the time. I am not entirely sure why this is a necessary consequence but the concentric ring structure is clearly visible.

Nikon AFS 50 mm f1.4 G,

Sigma AF 50 mm EX DG HSM f1.4,

Subset from the test picture right above: Sigma HSM 50 mm f1.4 DG, all lenses @f1.4, Light source at 2 m distance.

Nikkor AIS 50 mm f1.2 @f1.2, the f1.2 of the 50s shows slightly shaped OoF confusion discs where the brass housing of the lens intrudes into one lens element and reduces the diameter at one specific point. Its the only lens that I know that does this. Usually this is just invisible but the point light highlight clearly show this "feature". 

Nikon AFS 50 mm f1.4G @f1.4, just what one expects, clear and homogenous discs.

Sigma AF 50 mm f1.4 EX DG HSM @f1.4, the green discs show the problem with concentric rings clearly here.

If out of focus highlights with clean circles of confusion are the dominating graphical element in an image than the concentric ring features are obviously not desired and the Sigma could be the wrong lens for the job.

Both lenses - the Sigma as well as the Nikon - are designed with 9 well rounded aperture blades and the aperture stays nicely rounded until f4 or so. Most of the older 50 mm designs show edges when the diaphragm is closed to f2 or even to f1.8. On the other side: with the well rounded aperture blades its difficult to create star reflections of point light sources if the aperture is closed down to very large f-stops. But the Nikon AFS and the Sigma EX are obviously designed to be used wide open and that's where the differences are important.

Sigma AF 50 mm f1.4 EX DG HSM @f1.4, the green discs show the problem with concentric rings clearly here. But this test image also clearly shows that the background bokeh is very gradual and soft without any indication for hard edges. The rendering is painting like and probably is the best bokeh of all 50s (if no point light disc comes into the play here).

So to sum this up:

Go for the Nikon if OoF highlights are important for you and fast AFS is not relevant for your shooting style, go for the Sigma if you need the best bokeh but your don't care about the OoF highlight characteristics. If you need a bokeh king with fast AFS and perfect OoF highlight than I am afraid there is no perfect option available right now. I though about keeping both lenses but ended with sending both lenses back. I might opt for the Nikon later but I would like to see more samples from the Sigma first. I might update this review if sample variation plays a role with the OoF highlight rendering. There are indications that the concentric feature is not clearly visible with all Sigma 50s.

Want more opinions? Check this pages here:

- ByThom Review of the Sigma AF 50 mm EX DG HSM f1.4

- The Digital Picture Sigma Review

- Ryan Brenizer's Review of the Sigma

- Photozone Review

More sample images:

Above: Nikon AFS 50 mm f1.4 G, below: Sigma HSM 50 mm f1.4 DG, the Sigma shows smother (blurred) flowers without harsh edges.

Sigma HSM 50 mm f1.4 DG @f1.4 (the ring artefacts seem to be less prominent when the contrast is reduced, in this example the concentric ring artefacts come from traffic lights in 150 m distance)

Above: Sigma HSM 50 mm f1.4 DG @f1.4 with focus shifted from far to near.

Above: the scene in focus from the Nikkor

Above: Nikon AFS 50 mm f1.4 G @f1.4 with focus shifted from far to near.

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