The Sigma 18–250 mm OS had an opportunity to be tested on a spectrophotometer so we can present its transmission graph.
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%.
Please Support Us
If you enjoy our reviews and articles, and you want us to continue our work please, support our website by donating through PayPal. The funds are going to be used for paying our editorial team, renting servers, and equipping our testing studio; only that way we will be able to continue providing you interesting content for free.
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.
