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Testbench LENS TEST

I n AP 17 May, we tested the Sigma 50mm f/1.4 DG HSM Art lens and found it to be one of the best 50mm

optics, if not the best, that we have ever tested at AP. Yes, at around £850, the Sigma 50mm f/1.4 lens is expensive, especially when you

Zeiss Otus 55mm f/1.4 vs Sigma 50mm f/1.4It may be heralded as one of the best lenses ever made, but is the Zeiss Otus 55mm f/1.4 really worth almost £2,500 more than the Sigma 50mm f/1.4 Art lens? Richard Sibley and Andrew Sydenham put the lenses head to head

a 50mm f/1.4 lens. We would expect this type of lens to have between six and eight elements in five or six groups, yet the Sigma design features 13 elements in eight groups, and the Zeiss lens 12 elements in 10 groups. Obviously, this significantly adds to the size and weight of these lenses, which we will come to later. To find out more on the optical design of each lens, read Professor Bob Newman’s article on page 63.

Build and handlingNeither of the standard lenses on test here is particularly small in comparison to the respective optics from Canon and Nikon. In fact, the lenses are both very substantial. The Sigma 50mm f/1.4 weighs 815g, but the Zeiss Otus tops this with a weight of 970g. It is the no-compromise optical design of the lenses that is the reason for their size and weight.

In both cases it is more like carrying a 24-70mm f/2.8 zoom. If you are more used to shooting portraits with a 50mm f/1.8, the weight will make itself known on your forearms before too long.

With the Zeiss Otus being a manual-focus lens, this mechanism has to be of the very highest quality, and indeed it is. It is the smoothest focusing ring that I have ever used on any lens. It feels like it is gliding as you turn it.

While the focus ring of the Sigma lens isn’t as wide as the Zeiss, it does have a ridged grip to prevent slipping. The focusing mechanism itself feels a little more rigid and less fluid compared to the Zeiss. However, the Sigma 50mm f/1.4 manually focuses just as easily as the vast majority of premium lenses on the market. It has nice torque, it doesn’t slip or feel loose, and there are no clicks or whirrs from the cogs that engage with the AF motors.

compare it to the Nikon equivalent, the AF-S 50mm f/1.4 G, which costs just £280 – almost £570 less.

However, if you thought the Sigma lens was expensive, make sure you are sitting down when you hear the price of the Zeiss Otus 55mm f/1.4. It costs around

£3,170 and it doesn’t even feature autofocus.

FeaturesThe first thing to mention about each of these lenses is that the optical design is very different from the more typical design for

Zeiss Zeiss f/1.4 Zeiss f/5.6

Sigma f/1.4 Sigma f/5.6Sigma

Images taken from a real scene, and of our test chart, reveal that the Zeiss is slightly better in the corners when shooting at f/1.4. Pull-ups shown at 100% at 300dpi

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Our cameras and lenses are tested using the industry-standard Image Engineering IQ-Analyser software. Visit www.image-engineering.de for more details.

Mean = -0.4Max = -1.7

Our graphs

The MTF resolution chart shows clarity on the vertical axes and the number of line pairs per picture height (lp/ph) on the horizontal. As the lp/ph increases, the lens is less able to define them, hence the typical downward curve of an MTF chart.

To show vignetting, we use a 3D rendering. The brightest part of the lens, in the centre, is measured at 0EV. As the edges get darker, the corners drop, representing the scale of the darkening. A 1EV difference in brightness is shown in red.

The red arrows on the distortion grid show the direction and strength of the shift in the image, compared to the original point on the photographed chart. The Mean and Max values are given to show the average and worst point shift as a percentage value.

Resolution

Shading

Curvilinear distortion

Image qualityTo test the lenses and really see the differences between them, we used each of them with a Nikon D800E in a Nikon fit. Looking at the comparison images, you would be hard pushed to see the difference between the two lenses. With very careful focusing, and keeping the camera as steady as possible, you can see that in terms of centre resolution the Zeiss is better – just.

Both lenses provide lovely smooth out-of-focus areas that look fantastic, and the rounded aperture blades keep them looking that way, even when stopped down.

Regarding the edges of the image, again the Zeiss is the better of the two lenses, and is amazingly sharp in the very corners, even when wide open. However, at f/5.6, both lenses are as close to providing edge-to-edge sharpness as any lens we have seen.

When wide open, there is the merest hint of chromatic aberration visible when high-contrast edges are in the corner of the frame. Red and cyan can be seen in the Zeiss, and green and magenta in the Sigma, but to reiterate, it is only really noticeable if viewing at about

200% and if you are looking for it. In both cases it is simple to remove in software.

There is some vignetting from both lenses, although for many subjects it wasn’t an issue and actually helped to draw the eye to the centre of the frame, particularly when shooting portraits.

Putting real-life images to one side for a moment and looking at the resolution graphs, the shape of the graphs produced by each camera is strikingly similar. However, the Zeiss lens is fractionally better at each aperture, but again, only just.

ONE THING that is important when considering a lens that is manual focus only is just how well you can manually focus. This isn’t just down to your eyesight, but also the camera that you are using, and the subject matter of your images.

When shooting at an aperture of f/1.4, with the very shallow depth of field that comes with this, it only takes the focusing to be fractionally off for the subject to be slightly out of focus.

Another consideration is how the camera aids you to manually focus. Some cameras with live view will allow you to use a 100% pull-up, which is very precise, and you may also be able to use focus peaking to get an indication of the sharpest points of focus. AF indicators are also found in the viewfinders of most DSLRs.

It is vital to understand how these manual-focus aids work in your particular camera. Focus

peaking and the AF indicator systems often work over a small range of focus, rather than a particular point, so it is important to know where the precise point of focus is in that range. Check by taking a series of images at the largest lens aperture between where the focus peaking or indicators come on and go off. This should help you discover how to best use them to help manually focus your camera.

This portrait image shows just how difficult it can be to precisely manually focus a lens with the aperture set to f/1.4. Here the Zeiss is just a fraction off compared to the Sigma lens, which was autofocused

Full image

Zeiss

Sigma

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MANUAL FOCUSING

COMPARED to a proprietary 50mm f/1.4 lens, the Sigma version is expensive, although it is far cheaper than the Zeiss Otus 55mm f/1.4. When you pick up the Sigma lens, though, it quickly becomes clear why it costs what it does. The optical design of the Sigma has much more in common with the Zeiss lens than its cheaper equivalents, and it is this break away from a more traditional design that pays off with excellent image quality.

The images produced by the Sigma 50mm f/1.4 DG HSM Art lens display a staggering amount of detail, and the lens is as sharp in the corners as many lenses are in the centre. Better still, if you have a DSLR with an APS-C sensor, it becomes a great 75mm (equivalent) portrait lens and you will benefit from corner-to-corner sharpness with little difference across the frame.

Overall, the performance of the lens makes it one of the best lenses we have ever tested, and if you are in the market for a 50mm f/1.4 optic, then the Sigma is worth spending a little extra money on. It is already an early candidate for Fixed Lens of the Year at the 2015 AP Awards.

Testbench LENS TEST

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NO EXPENSE has been spared in the production of the Zeiss Otus 50mm f/1.4 lens. It has an extremely high-quality construction that can be physically felt when you focus the lens. Its engineering makes this one of the best lenses to manually focus that we have ever used. It really is a fantastic piece of glass.

In terms of image quality, the Zeiss Otus 50mm f/1.4 lens will be difficult to beat in terms of resolution and distortion, and out-of-focus areas are rendered beautifully. There is some vignetting wide open, but this is expected, and more important is how sharp the lens is when shooting wide open. However, all this comes at a very obvious price.

The money spent on the Zeiss Otus could buy a Nikon D800 and a Sigma 50mm f/1.4 DG HSM Art lens, with enough left over for another lens or a flash. And let’s not forget that the Zeiss lens does not feature autofocus, which will make it awkward to use for some photographers and subjects. However, when we score, we don’t account for the price of a product, we simply judge it on how well it performs, and in this regard the Zeiss lens is exceptional.

Filter diameter 77mmLens elements 12Groups 10Diaphragm blades 9Aperture f/1.4-16Minimum focus 50cmLength 141mmDiameter 83mmWeight 970gLens mount Canon EF, Nikon F

Data file

GOLD

Filter diameter 77mmLens elements 13Groups 8Diaphragm blades 9Aperture f/1.4-16Minimum focus 40cmLength 99.9mmDiameter 85.4mmWeight 815gLens mount Canon EF, Nikon F, Sony A, Sigma

Data file

GOLD

ALL P

RICE

S AR

E STR

EET P

RICE

S

It’s expensive, but it is one of the best standard lenses ever made

A reasonably priced lens offering outstanding image quality

A few other options if you are interested in a 50mm f/1.4 lens

Zeiss Otus 55mm f/1.4l £3,170

Sigma 50mm f/1.4 Artl £850

Canon 50mm f/1.4 EF USMl Reviewed 20 July 2013 l £280

CANON’S 50mm f/1.4 lens is something of a good all-rounder, with a reasonable performance when shooting wide open, although it does lack the bitingly sharp resolution of the two 50mm lenses on test here. When shooting between f/2.8 and f/11, there is little difference in sharpness between the centre of the image and the corners, although to get the most from the lens it is best to shoot at f/8. There is also some curvilinear distortion at the edges of the frame that will require straightening. A very good, reasonably priced lens for Canon users.

Zeiss Planar T* 50mm f/1.4 l Reviewed 20 July 2013 l £600

IF YOU hanker after a Zeiss lens, but the Otus is out of reach, the Planar T* 50mm f/1.4 may be the answer. Available in Canon EF and Nikon F mounts, the lens has a solid metal construction and, like the Otus, is manual focus only.

In terms of image quality, it is superb when shooting at f/8-11, but is let down by poor performance when shooting wide open. The lens also suffers from far more curvilinear distortion than both the lenses on test here.

Nikkor AF-S 50mm f/1.4Gl Reviewed 20 July 2013 l £300

NIKON’S current Nikkor AF-S 50mm f/1.4G lens is around the same price as the Canon equivalent and performs roughly on a par. Curvilinear distortion is a little less, although vignetting is around 0.3EV worse in the corners. The latest optical lens coatings ensure that the Nikkor lens has a good level of contrast, and it is very good wide open. Once again, to get the best from the lens you need to be shooting at between f/8 and f/11.

Alternatives

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Resolution

Shading

Curvilinear distortion

The Sigma 50mm f/1.4 DG HSM Art lens resolution chart is almost identical to that of the Zeiss lens. However, there is more of a spread in the resolution at different apertures, where the Zeiss lens is more consistent, with the lines closer together. The Sigma lens does show impressive corner sharpness when shooting at f/5.6.

Sigma’s 50mm f/1.4 performs slightly better in terms of corner shading when shooting at f/1.4. The very corners of the lens are around 0.6EV darker than the centre, but like the Zeiss lens, by f/2.8 the vignetting is reduced to 0.25EV and less than 0.1EV by f/4.

Interestingly, the Sigma 50mm f/1.4 shows pincushion distortion that is usually associated with telephoto lenses, as opposed to the barrel distortion of the Zeiss lens. However, the amount of distortion is again remarkably similar in terms of strength, it just occurs in the opposite direction.

Mean = 0.1Max = 0.5

Resolution

Shading

Curvilinear distortion

The resolution chart shows that the Zeiss Otus 55mm f/1.4 is among the best lenses we have ever tested. At f/5.6-8, the lens is supremely sharp in the centre, and it is almost as good at the edges. The graph doesn’t quite do justice to just how good this lens is at the edges of the frame.

Both lenses show quite severe vignetting when shooting wide open. At the very edges of the frame, the Zeiss 55mm lens is around 0.75EV darker than the centre when shooting wide open, but by f/2.8 the vignetting is reduced to 0.25EV and less than 0.1EV by f/4.

There is some slight barrel distortion on the Zeiss 55mm f/1.4 lens, although it really is nothing to be concerned about. With a mean distortion of just -0.3EV and a maximum of -0.7EV at the very edges, any distortion should be easily corrected using image-editing software.

Mean = -0.3Max = -0.7

GOLD GOLD

Zeiss Otus 55mm f/1.4

Sigma 50mm f/1.4 Art WHILE I fully appreciate that few, if any of you,

are going to withdraw £3,170 from the bank and head out to buy the Zeiss Otus 55mm f/1.4 lens, I hope this test has shown that there are occasions where differences in image quality are not proportional to price.

There comes a point where differences are so slight that, even if you were considering spending £3,170 on the Zeiss Otus lens, you may stop to think about whether you actually need it, and whether the Sigma 50mm f/1.4 DG HSM Art lens is actually more than good enough.

The Zeiss lens needs to be manually focused, and while this is a joy to do with the large focusing ring, it does take time, good eyesight and for absolute precision it will also require a camera with a good viewfinder or a 100% magnification live view screen. The Zeiss lens does resolve more detail than the Sigma 50mm f/1.4 lens at both the centre and the edges, but not enough to warrant the average enthusiast even contemplating buying it.

In summary, the Zeiss Otus 55mm f/1.4 lens is superb. It really is a triumph of lens design. It is going to take a lot of hard work for any manufacturer to better it, and for this reason it has to be awarded five stars. However, whether or not you should buy one is another question, and one to which I think the answer is obvious. If you want to try the Zeiss Otus 55mm f/1.4, I would suggest that you rent it for a weekend from www.hireacamera.com – which very kindly lent us the lens we tested in this review.

As for the Sigma 50mm f/1.4, it also is a triumph. Everyone in the AP technical team has been impressed with the lens, and a few have already added it to their own wish lists. Sigma’s designers have managed to match the central image quality of the Zeiss lens, but at a quarter of the price. And for that reason it, too, scores five stars, and, like the Zeiss Otus, is worthy of an AP Gold Award.

Our verdict

‘The Zeiss Otus 55mm f/1.4 lens is superb. It really is a triumph of lens design’

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