An affordable, high-performing macro lens that is also ideal for copying.Sigma's 50mm f/2.8 EX DG has the shortest focal length and lowest price of the four macro lenses in the company's current line-up. Designed for use with full frame digital SLR cameras, it can also be fitted to DSLRs with smaller APS-C size sensors, where it covers a similar field of view to a 75mm lens in 35mm format with Nikon, Pentax and Sony cameras or 80mm with Canon cameras. . . [more]
Sigma's 50mm f/2.8 EX DG has the shortest focal length and lowest price of the four macro lenses in the company's current line-up. Designed for use with full frame digital SLR cameras, it can also be fitted to DSLRs with smaller APS-C size sensors, where it covers a similar field of view to a 75mm lens in 35mm format with Nikon, Pentax and Sony cameras or 80mm with Canon cameras.
The DG (‘digital') designation indicates specially-developed lens coatings that minimise the effects of internal reflections off the surface of the sensor. The EX (‘Excellence') tag denotes a special matte finish that provides a better grip and adds a touch of class to the appearance of the lens.
The Sigma 50mm f/2.8 EX DG Macro lens, shown without its screw-in lens hood. (Source: Sigma.)
No exotic glass elements are included in the optical design, which comprises 10 elements in 9 groups. Typically for a true macro lens, this lens has a floating internal focus system, which helps to correct aberrations across the magnification range. True 1:1 magnification is reached at a focus distance of 188 mm, which is pretty close. Such a short working distance makes it unsuitable for photographing easily-spooked subjects.
The Sigma 50mm Macro lens looks very smart and feels solidly built. With a weight of 320 grams and length of 64 mm at infinity focus it's also very compact. The lens barrel extends by about 36 mm at the closest focus but the front element doesn't rotate, allowing angle-critical attachments to be used.
The inner barrel carries prominent markings showing six magnification ratios, ranging from 1:1 when it's fully extended to 1:5 when it's pulled right in. These guides are handy for photographers who wish to shoot with specific magnification ratios.
A 22 mm wide focusing ring is located close to the front of the lens. It carries a 9 mm wide ridged rubber band that provides a secure grip. Distance markings in metres and feet are stamped on the ring behind this band. The focusing ring rotates through approximately 180 degrees, enabling accurate manual focusing.
Focusing is nicely smooth in Manual mode but a clutch is applied in AF mode preventing manual focusing. Manual over-ride of autofocusing is not supported. Note: This lens is not compatible with Nikon's D40, D40x, D60, D3000 and D5000 which lack AF motors in the camera body.
Autofocusing is driven by the motor in the camera body and a conventional AF/MF switch is located close to the camera for swapping focus modes. Between this switch and the focusing ring is an AF limiter slider with two positions: Limit and Full. The Limit position restricts the normal focusing range to between 188 mm and 235 mm to minimise hunting with close subjects.
The front element is recessed about 10 mm into the lens barrel, protecting it from dust, scratches and sticky fingers. Sigma provides a slim, cylindrical lens hood that screws into a threaded section near the front of the barrel. (Threading for the filter is a little further in.) Aside from the hood, only front and end caps are provided.
The lens hood is tricky to attach and makes it difficult to fit the lens cap when it is in place and it doesn't reverse neatly over the end of the lens for storage. The inner side of the hood is threaded so it may be possible to fit 72 mm diameter filters when the hood is in place. However, not having a suitable filter to try, we can only speculate.
We conducted our tests of this lens on the EOS 5D, the standard body we use for testing all lenses of this type. The mounting plate attached to the body positively and securely and, despite its compact size and light weight, the lens felt nicely balanced and comfortable to use.
While the small size and light weight make this lens easier to use hand-held than longer focal length lenses. However, its extremely short working distance requires special care and attention when shooting with a 1:1 magnification ratio. With the barrel fully extended, the front of the lens hood almost touches the subject. This can cause shading of part or all of the subject and makes it impossible to use the camera's on-board flash unit for flash fill. (A ring flash may be usable, provided its output level could be controlled.)
Swapping between manual and autofocusing was comparatively easy and the AF motor was quiet and reasonably fast for a macro lens - although it couldn't be classified as high-speed. Hunting only occurred when we photographed small, low-contrast subjects at high magnification in low light levels.
At a pinch this lens could be used for portraiture on an APS-C sensor, although a longer focal length would be more suitable for portrait photography. Instead, its high resolution and flatness of field make it ideal for copying work, particularly with DSLR cameras that have 36 x 24mm image sensors.
The Sigma 50mm f/2.8 EX DG Macro produced the highest resolution and second lowest chromatic aberration of the four macro lenses we reviewed in late July and early August 2010. Our Imatest tests on JPEG files taken with the Canon EOS 5D body showed it exceeded expectations for the camera's sensor with the peak resolution at f/9 and very high resolution between f/4.5 and f/16.
Differences between centre and edge resolution were small throughout the aperture range, indicating excellent flatness of field - as you would expect from a high-quality macro lens. The graph below shows the results of our tests across the aperture range of the review lens.
Lateral chromatic aberration was negligible also negligible at most aperture settings, ranging into the ‘low' band at the two widest apertures. This, again, is a characteristic of a good true macro lens. In the graph below, the red line marks the boundary between ‘negligible' and ‘low' CA.
Distortion was also negligible. We found slight vignetting at the widest apertures but it was gone by f/4, another expected characteristic. Bokeh was attractive, both at wide apertures and with the aperture stopped down, as is evident in the sample images below.
It was possible to force the lens to flare by pointing it directly towards a bright light source. However, normal backlighting created no problems and produced some attractive results.
Buy this lens if:
- You're comfortable with short working distances.
- You want an affordable macro lens that delivers sharp images at mid-range aperture settings.
- You require edge-to-edge sharpness for copying.
- You want competent auto and manual focusing.
- You want a lens that requires no readjustment when you fit filters.
- You'd like a lens that delivers attractive bokeh.
Don't buy this lens if:
- You want to photograph live insects and other small, mobile animals (the working distance is too short).
- You need a general-purpose lens that can be used for portraiture.
- You require built-in image stabilisation.
- You're not prepared to use a tripod for critical macro work.
Based on JPEG files taken with the Canon EOS 5D:
Taken with the Canon EOS 5D:
Vignetting at f/2.8.
Vignetting at f/4.
Camera on tripod; 1:1 reproduction of a postage stamp; ISO 200, 1/100 second at f/3.5.
Camera on tripod; ISO 200, 1/790 second at f/2.8.
Camera on tripod; ISO 200, 1/332 second at f/4.
Camera on tripod; ISO 200, 1/166 second at f/5.6.
Camera on tripod; ISO 200, 1/100 second at f/8.
Camera hand-held; ISO 200, 1/30 second at f/8. 1:1 reproduction ratio.
Camera hand-held; ISO 200, 1/197 second at f/8. 1:1.2 reproduction ratio.
Camera hand-held; ISO 800, 1/83 second at f/2.8. 1:1 reproduction ratio.
Forced flaring; camera hand-held; ISO 200, 1/250 second at f/2.8.
Backlighting; camera hand-held; ISO 400, 1/250 second at f/2.8.
Camera hand-held; ISO 400, 1/395 second at f/2.8.
Camera hand-held; ISO 400, 1/41 second at f/2.8.
Camera hand-held; ISO 400, 1/395 second at f/6.4.
Camera hand-held; ISO 400, 1/100 second at f/6.4. 1:1 reproduction ratio.
Camera hand-held; ISO 800, 1/125 second at f/5.6. 1:1 reproduction ratio. (Subject is approximately 3 mm in length.)
The same subject, taken with the lens on a Canon EOS 40D body, showing the effect of the crop factor of the smaller sensor; camera hand-held; ISO 800, 1/50 second at f/8.
Picture angle: 46.8 degrees
Maximum aperture: f/2.8
Minimum aperture: f/32
Lens construction: 10 elements in 9 groups
Lens mounts: Canon, Nikon (not fully compatible with D40, D40x, D60, D3000, D5000), Pentax, Sigma, Sony/Minolta
Diaphragm Blades: 7
Focus drive: Micro-motor
Minimum focus: 188 mm
Maximum magnification: 1:1
Filter size: 55 mm
Dimensions (Diameter x L): 71.5 x 64 mm
Weight: 320 grams
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