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Lens review

Sigma 18-125 mm f/3.8-5.6 DC OS HSM

4 September 2009
Szymon Starczewski

9. Ghosting, flares and transmission

As far as the transmission of light is concerned, we have nothing against the amateur Sigma. Although there are no reasons to praise, either. The most light, 90%, goes through the lens at around 630 nm wavelength. In the middle of visible spectrum (i.e. around 550 nm) it’s 85%. This level remains for green light and begins to drop for blue one, to reach slightly less than 70% for violet.

Sigma 18-125 mm f/3.8-5.6 DC OS HSM - Ghosting, flares and transmission

Losing so much light for blue and violet light doesn’t instill optimism, but we need to remember two things. Firstly, Sigma is a cheap amateur instrument and it’s hard to expect any wonders from the highest class. Secondly, we’re dealing with twelve groups of lenses here, so there were 24 air-glass boundaries to cover. The maximum transmission reaching 90% means that there are 0.4-0.5% loses of light on one boundary, which is a relatively good result.

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Sigma doesn’t really emphasize the great work against bright light, while my impressions are that this producer performs the best in this category of all the companies. The amateur Sigma 18-125 mm OS doesn’t bring shame on the producers and performs quite well. Light artifacts are obtainable at every focal length, but it’s not that easy and the reflections themselves are not intense and aren’t blatant.


Sigma 18-125 mm f/3.8-5.6 DC OS HSM - Ghosting, flares and transmission

Sigma 18-125 mm f/3.8-5.6 DC OS HSM - Ghosting, flares and transmission

Sigma 18-125 mm f/3.8-5.6 DC OS HSM - Ghosting, flares and transmission

Sigma 18-125 mm f/3.8-5.6 DC OS HSM - Ghosting, flares and transmission