Sigma 18-250mm f/3.5-6.3 DC Macro OS HSM Lens


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    Sigma 18-250mm f/3.5-6.3 DC Macro OS HSM Lens

      In Summary

      Buyers of all-in-one zoom lenses will welcome the arrival of Sigma’s 18-250mm F3.5-6.3 DC Macro OS HSM lens, which has just been released. Smaller and lighter than its predecessor, which we reviewed in May 2009, it is designed exclusively for DSLR cameras with APS-C sized sensors. This lens has been released initially with a Canon mount but mounts for Sigma, Sony, Nikon, and Pentax will follow.

      Buy this lens if:
      - You want a lightweight all-round lens with a competitive price tag.
      - You want a zoom lens that can be used with polarisers and graduated filters.
      - You require good flare resistance in backlit situations.
      - You want effective image stabilisation for both the viewfinder image and the capture system.

      Don't buy this lens if:
      - You have a camera with a 'full frame' (36 x 24mm) image sensor.
      - You need a fast lens across the focal length range for shooting action in dim lighting.

      Full Review

      Buyers of all-in-one zoom lenses will welcome the arrival of Sigma’s 18-250mm F3.5-6.3 DC Macro OS HSM lens, which has just been released. Smaller and lighter than its predecessor, which we reviewed in May 2009, it is designed exclusively for DSLR cameras with APS-C sized sensors. This lens has been released initially with a Canon mount but mounts for Sigma, Sony, Nikon, and Pentax will follow.

      Sigma's new 18-250mm F3.5-6.3 DC Macro OS HSM lens. (Source: Sigma.)

      Use of a new Thermally Stable Composite (TSC) material in the lens barrel has enabled Sigma to make a lens that's both smaller and lighter. TSC withstands dimensional changes in the internal and external barrels due to extreme temperature variations, which means it shouldn't be affected by heat when used outdoors in summer. 

      The other significant improvement is the addition of 'macro' focusing, which reduces the minimum focusing distance by 10 cm to 35 cm and provides a maximum magnification of 1:2.9 (roughly 1/2 life size with APS-C sensor size). The maximum magnification ratio is stamped on the internal lens barrel where it is revealed as you zoom the lens in from wide to tele positions. 

      Like its predecessor, the new lens covers focal lengths from the 35mm equivalent of 27mm to 375mm with most camera brands (28.8mm to 400mm on Canon bodies) and offers a 13.8 times zoom ratio. The table below compares the new lens with the previous model.

       

      18-250mm f/3.5-6.3 DC Macro OS HSM

      18-250mm f/3.5-6.3 DC OS HSM

      Lens construction

      16 elements in 13 groups (includes one SLD element and three aspherical elements)

      18 elements in 14 groups (includes four SLD elements and three aspherical elements)

      Minimum focus

      35 cm

      45 cm

      Maximum magnification

      1:2.9

      1:3.4

      Filter size

      62 mm

      72 mm

      Dimensions (Diameter x L)

      73.5 x 88.6 mm

      79 x 101 mm

      Weight

      470 grams

      630 grams

      Although the aperture ranges of both lenses are identical, the optical construction of the new lens is simpler, with only 16 elements in 13 groups. There are three aspherical glass elements (two of them double-sided) and one Special Low Dispersion (SLD) glass element to correct common aberrations. Super Multi-Layer Coating has been applied to internal surfaces to minimise flare and ghosting.

      A built-in Hybrid Optical Stabiliser counteracts camera shake both when shooting and in the viewfinder image. Internal focusing allows users to fit angle-critical attachments like polarisers and graduated filters

      Autofocusing is driven by the same Hyper Sonic Motor (HSM) as used in the previous model.  A rounded, seven-bladed iris diaphragm closes to a circular aperture to create attractive bokeh at wide aperture settings. 

      Build and Ergonomics
      Despite its lighter weight, the new lens has the solid feel that is typical of Sigma lenses. Its weight and size made it a better match for the Canon EOS 1100D than the larger and heavier EOS 40D, so we used the former body for our tests.

      Extending approximately 87 mm from the camera body (without the lens cap attached), this lens protrudes a further 72mm when zoomed to the 250mm focal length. The design consists of three barrels, the innermost containing the optical elements, the middle one engraved with 'macro' reproduction ratios that range from 1:2.9 at full zoom extension to 1:9.5 at the 18mm focal length.

      The focusing and zoom rings are mounted on the outer barrel. The former is approximately 16 mm wide with an 8 mm wide ridged, rubber grip band. Engraved on the ring just behind this band are distance markings in feet and metres ranging from the closest focus to infinity. In manual focusing mode, these distances can be lined up against a mark on the fixed section of the barrel behind. 

      The zoom ring is approximately 38 mm wide and located between the focusing ring and the camera. It has a 25 mm wide ridged rubber grip band and its trailing edge carries the branding and name of the lens plus markings for the 18mm, 28mm, 35mm, 50mm, 80mm, 135mm and 250mm focal lengths. These are lined up against a white mark on the non-moving part of the lens barrel close to the camera.

      On the left side of the main barrel are two sliders; one for switching between auto and manual focusing and the other (further around the barrel) for stabilisation. A zoom lock is located at the rear of the zoom ring, just above the AF/MF slider. Filters screw into the 62 mm threaded ring in front of the front element.

      The OS image stabilisation system has only two modes: on and off. You can't set stabilisation to operate in only one direction to get the best results with panning shots but the system appeared to handle panning reasonably well. The stabilised viewfinder image makes it easier to compose both pans and normal shots with longer focal length settings.

      A chromed brass bayonet mount ensures long-term stability and accurate connection between the lens and camera body. The lens comes with a petal-shaped, hard plastic hood that extends its overall length by about 40 mm when fitted and reverses over the lens for storage. The supplied lens cap clamps firmly into place with spring-loaded clips.

      Performance
      Although no match for a high-quality prime lens (or even shorter zoom), the review lens turned in a good all-round performance for its type and price tag. Overall image sharpness was a cut above many extended-range zooms we've tested and the Sigma lens was relatively free of common aberrations.

      Autofocusing was fast, accurate and quiet in most shooting situations, making this lens suitable for photographers who shoot movies with their DSLRs. Hunting was less common in low light levels than we found with the previous model.  

      Imatest showed the review lens to be capable of meeting expectations for the EOS 1100D's 12.2-megapixel sensor (or coming quite close) at all the focal lengths we were able to measure. It also provided a more consistent overall performance than the previous model. (As before, lack of space in our test set-up prevented us from evaluating performance at the 250mm focal length setting.) 

      The best performance occurred between f/4.5 and f/6.3, with the 35mm focal length delivering the highest resolution at f/4.5. Edge softening was evident at shorter focal lengths, with the gap between centre and edge resolution narrowing by the 35mm focal length. The graph below shows the results of our Imatest tests.

      We found lateral chromatic aberration to be somewhat lower in the new lens. Whereas the older lens was mainly in the low-to-medium range, the new lens dipped into the negligible band at all but the two shortest focal lengths and never strayed into the medium range. In the graph of our Imatest tests below, the red line marks the boundary between negligible and low CA values, while the green line separates low from moderate CA.

      Although it was possible to force the lens to flare, internal reflections and scattering were generally low, thanks to the internal surface coatings and an excellent lens hood. Shots taken in relatively strong backlighting showed very little loss of contrast and colour fidelity was well maintained. 

      Slight vignetting was observed with the widest apertures at all focal length settings. As with the previous lens, closing the aperture by one f-stop eliminated this problem.

      Barrel distortion was visible at 18mm but by 50mm pincushion distortion began to appear. Fortunately, neither vignetting nor distortion was severe enough to affect the kinds of shots most potential purchasers of this lens would take and both are easily corrected with a moderately capable image editor.

      Close-up performance was a real improvement over the previous lens. Not only was it possible to focus closer; the new lens delivered better bokeh than its predecessor, particularly at longer focal length settings with the lens stopped down.

      As before, we found the OS system could provide up to four f-stops of shutter speed advantage for general shooting, enabling us to use shutter speeds slower than 1/60 second with moderate zoom settings when subjects were brightly lit and/or high ISO settings were used. It was particularly effective for close-ups.

      Conclusion
      With its relatively low price tag and great versatility, the Sigma 18-250mm f/3.5-6.3 DC Macro OS HSM represents a worthwhile all-in-one solution for everyday picture-taking. It's also an excellent choice for travellers who want a single lens to pair with an entry- or mid-level DSLR camera body.

      Buy this lens if:

      - You want a lightweight all-round lens with a competitive price tag.
      - You want a zoom lens that can be used with polarisers and graduated filters.
      - You require good flare resistance in backlit situations.
      - You want effective image stabilisation for both the viewfinder image and the capture system.

      Don't buy this lens if:
      - You have a camera with a 'full frame' (36 x 24mm) image sensor.
      - You need a fast lens across the focal length range for shooting action in dim lighting.

      SPECS

      Picture angle: 76.5 to 6.5 degrees
      Minimum aperture: f/22
      Lens construction: 16 elements in 13 groups (includes one Special Low Dispersion (SLD) element and three aspherical elements)
      Lens mounts: Canon EF, Nikon F, Pentax K, Sigma SA and Sony Alpha
      Diaphragm Blades: 7 (rounded aperture)
      Focus drive:  Hyper Sonic Motor (HSM)
      Stabilisation: Approx. 4 stops of correction (Canon, Nikon and Sigma mounts only)
      Minimum focus:  35 cm
      Maximum magnification: 1:2.9
      Filter size:  62 mm
      Dimensions (Diameter x L): 73.5 x 88.6 mm
      Weight: 470 grams

      RRP: AUD$699; US$850
      Distributor: C.R. Kennedy & Company; (03) 9823 1555; www.crkennedy.com.au.

      TESTS

      Based on JPEG files taken with the Canon EOS 1100D.

       

      SAMPLES

      Vignetting at 18mm.

      Vignetting at 50mm.

      Vignetting at 250mm.

      Rectilinear distortion at 18mm.

      Rectilinear distortion at 50mm.

      Rectilinear distortion at 250mm.

      18mm focal length, ISO 100, 1/200 second at f/8.

      35mm focal length, ISO 100, 1/200 second at f/8.

      50mm focal length, ISO 100, 1/250 second at f/8.

      250mm focal length, ISO 100, 1/250 second at f/8.

      Close-up at 250mm; ISO 200, 1/80 second at f/6.3.

      Close-up at 250mm; ISO 800, 1/30 second at f/16.

      Flare; 18mm focal length, ISO 100, 1/500 second at f/8.

      Strong backlighting outside image frame; 28mm focal length, ISO 100, 1/125 second at f/11.

      Backlighting behind subject; 18mm focal length, ISO 100, 1/80 second at f/9.

      Stabilisation test; 61mm focal length, ISO 200, 1/13 second at f/5.6.

      37mm focal length, ISO 200, 1/125 second at f/7.1.

      250mm focal length, ISO 100, 1/125 second at f/7.1.

      Rating

      RRP: AUD$699; US$850

      • Build: 8.8
      • Handling: 8.5
      • Image quality: 8.5
      • Versatility: 9.0

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