LensTip.com

Lens review

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

12 April 2011
Arkadiusz Olech

9. Ghosting, flares and transmission

The Sigma 18–250 mm OS had an opportunity to be tested on a spectrophotometer so we can present its transmission graph.

Sigma 18-250 mm f/3.5-6.3 DC OS HSM - Ghosting, flares and transmission

As you can notice, the most of light is transmitted for red colour – the optical system lets 94- 95% of it in. The colour rendering is not completely natural, though, because the transmission decreases when we move to shorter wavelengths. For green-yellow light the transmission amounts to just a tad above 90% and for blue light it decreases to near 85%.


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To assess the quality of the coatings, used in the Sigma, you must take into account the number of air-to-glass surfaces which had to be coated. Here we have as many as 28 of them. It is a huge amount so if you want to get a transmission on the level of 95% you can’t lose more than 0.2% of light on one such surface. It means the lens should be equipped with coatings of the highest quality. The efficiency of the coatings is a bit worse for blue light but even there on one surface we lose about 0.6% of light – such a result is still quite decent.

We usually praise Sigma lenses for work against bright light but this time there will be no praise – the tested lens fares badly in this category. You can understand why looking at the photos below.

Sigma 18-250 mm f/3.5-6.3 DC OS HSM - Ghosting, flares and transmission

Sigma 18-250 mm f/3.5-6.3 DC OS HSM - Ghosting, flares and transmission

Sigma 18-250 mm f/3.5-6.3 DC OS HSM - Ghosting, flares and transmission

Sigma 18-250 mm f/3.5-6.3 DC OS HSM - Ghosting, flares and transmission

Sigma 18-250 mm f/3.5-6.3 DC OS HSM - Ghosting, flares and transmission