The Sigma's task in this category was very difficult indeed. It's worth reminding that the lens features a big front element hardly sheltered by the edge of the tube and as many as 22 optical groups. In practice it means the light can be reflected by as many as 44 air-to-glass surfaces! If you add to that the new 1.4x converter the number of groups increases to 27 and the number of surfaces – to 54. In order to imagine the scale of the problem let's assume that Sigma employed top-of-the-range coatings which, for light falling straight on, lose just 0.3% of brightness on one surface. When you deal with 54 air-to-glass surfaces the transmission of the instrument still amounts to 85%, even without adding losses connected to light absorption in glass.
Small wonder the performance against bright light is the worst with the teleconverter attached to the lens. You can get shots completely spoiled by ghosting and flares but only if the sun is positioned right outside the frame corner.
At 70-135 mm focal lengths the performance against bright light can be called quite sensible, of course only taking the difficulty level into account. It decreases at 200 mm but in that case situations when the sun is close to the frame corner won't happen very often. What's more, the lens fares equally well as its predecessor which had only 17 groups so 10 air-to-glass surfaces less to cover.
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.
