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Lens review

Canon EF 85 mm f/1.8 USM

8 March 2011
Arkadiusz Olech

9. Ghosting, flares and transmission

The transmission of the Canon EF 85 mm f/1.8 USM was tested on an optical table with the use of a spectrophotometer. Its graph, depending on wavelengths, is presented below.

Canon EF 85 mm f/1.8 USM - Ghosting, flares and transmission

It would be difficult to complain about anything here. In a quite wide range - from 450 to over 650 nm - the transmission reaches over 90%, being at its peak (92%) for green-yellow light. Taking into account the fact that there are 7 groups of elements in the tested lens so we deal here with 14 air-to-glass surfaces, you can calculate easily that on one surface we lose about 0.6% of light. Such a result doesn’t bowl us over because lenses with the best anti-reflection coatings, produced nowadays, can get to the level of 0.2%. Such coatings, though, are used only in devices from the top-end price segment and the Canon EF 85 mm f/1.8 USM doesn’t belong there for sure. On the other hand, though, the Samyang 1.4/85, cheaper than the Canon, featured better coatings because in its case the transmission could even reach as much as 98%.

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The photos below show how the Canon fares against bright light. Artifacts are visible both on the APS-C sensor and on full frame. Fortunately they are not especially big.

Canon EF 85 mm f/1.8 USM - Ghosting, flares and transmission

Canon EF 85 mm f/1.8 USM - Ghosting, flares and transmission