Sigma 18–250mm f/3.5-6.3 DC OS MACRO: Jack of All Trades

The Sigma 18–250mm f/3.5-6.3 DC OS MACRO

Ambarin Afsar finds out whether Sigma’s latest superzoom offering, the 18–250mm f/3.5-6.3 DC Macro OS HSM, lives up to the promises it makes.

Superzoom lenses are always very interesting for me. I like the freedom to go from wide to tele in a matter of seconds. These allin- one lenses are something that third-party manufacturers keep updating and reworking, so much so that they end up giving better value than proprietary lenses. The Sigma 18–250mm f/3.5-6.3 DC Macro OS HSM is one such update.

Features
The 18–250mm Macro OS HSM offers two main updates over its predecessor, the 18–250mm DC OS HSM. These are improved close-up capabilities and a much reduced size and weight. The updated lens offers a magnification ratio of 1:2.9 while its predecessor offered a ratio of 1:3.8. Its competitor, the Tamron 18–270mm f/3.5-6.3 Di II VC PZD, also offers a ratio of 1:3.8.

The lens features a maximum aperture of f/3.5-6.3 and 16 lens elements in 13 groups. It also features a Hypersonic Motor for quiet focusing, and focuses on entry-level Nikon bodies. It is optically stabilised, and the manufacturers promise a 4-stop advantage.

Sigma has also limited the minimum aperture to f/22, in order to help prevent degradation of image quality. On the other hand, Tamron offers f/40 at the telephoto end.

Handling
The 18–250mm reminds me a lot of the Tamron 18–270mm in terms of design, size and build quality. The lens is lightweight, with a solid plastic barrel.The zoom and focus rings operate quite smoothly.

The lens also features a depth-of-field scale and an image magnification scale. The lens features two switches on the left side of the barrel. These control AF and OS, while there is another smaller button located on the zoom ring to lock the lens at 18mm for transport and to avoid zoom creep. All three buttons can be reached quite easily.

I did find the lens suffering from a lot of zoom creep, when pointed downwards. Sigma would do better to make the zoom ring more resistant to this.

Additionally, what I found unnecessarily lacking was a full time manual focus override option. I do not know why this could not have been included and seems quite irksome to me, especially since the lens has macro capabilities.

Performance
The autofocus is very quiet and impressively fast, even at the telephoto end. I found the Sigma’s AF system to be faster than competing lenses from third-party manufacturers. My observations about the sharpness of the lens are slightly mixed. At 18mm, sharpness is average in the centre and quite soft towards the edges of the frame when the lens is wide open. However, stopping down to f/5.6 improves centre and corner sharpness drastically.

If you want optimum sharpness at 135mm, it would be best to further stop down to f/8 and f/11. At 250mm, detail suffers a little, and if you want peak image quality, you will necessarily have to stop down to f/11.

Vignetting is apparent only at the maximum apertures throughout the zoom range, and stopping down by one stop eliminates it entirely.

What was surprising was the amount of pincushion distortion that I observed at 35mm. This gets better as you progress towards 135mm and 250mm. There is the usual barrel distortion, which is to be expected at 18mm.

Chromatic aberration is reasonably low. It is most noticeable at the wide angle, where there is some red and purple fringing towards the corners of the frame. This lessens when you move to mid-range focal lengths and becomes apparent at the extreme tele end again.

Shot at 62mm, this image displays a lot of pincushion distortion. Exposure: 1/1000sec at f/8 ISO: 400 Photograph/Ambarin Afsar

Conclusion
Priced at Rs. 30,500, this lens is complete value for money. It offers you macro capabilities, a good autofocus system and a large zoom range. While its Tamron rival is also a wonderful performer, it is priced a little too expensively. On the other hand, you have to make do with slow apertures—a trade-off, which seems palatable, given the price.