Sigma 30 mm f/1.4 EX DC HSM review - Ghosting, flares and transmission

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Sigma 30 mm f/1.4 EX DC HSM

18 August 2009

Arkadiusz Olech

9. Ghosting, flares and transmission

The amount of unwanted flares generated when working against bright light depends mainly on the quality of anti-reflection coatings and the optical and mechanical construction of the lens itself. If only those two factors had an influence, we shouldn’t expect major differences between Sigmas of different mounts. As we’ll find out in a moment the differences exist, and a few factors can be blamed for that. The impact here may have the kind of filter used before the camera’s sensor, the quality of microlenses of the sensor and also a varying, bayonet from bayonet, length of the rear lens from the sensor itself.

Let’s start with a transmission curve depending on the wavelength, which we show in the picture below.

Sigma 30 mm f/1.4 EX DC HSM - Ghosting, flares and transmission

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You can see that the recorded results are really high. Taking into consideration that we’re dealing with 7 groups of lenses here, so 14 air-glass boundaries to coat with layers, the results are really good. In the red range we reach a very high 97% level, in the middle of the visible range we’re at 94-95% and only in the blue part of the spectrum we can have some reservations, as there the transmission falls below 90%. The general picture is very positive, though.

Sigma’s behavior when working against bright light is good, or even great. In the case of Canon, Nikon, Pentax and Sony we were unable to “catch” any serious artifacts, regardless if the light source was the Sun or a strong light of street lamps, and if the lens worked wide open or closed down.

The effect came after mounting Sigma on Olympus and closing it down noticeably. Placing the Sun in the corner of the frame resulted in a uniform green flare’s appearance, the kind of which we present in the picture below.