Laowa 105mm f/2 (T3.2) STF – Features
The lens’s Smooth Trans Focus design renders out-of-focus highlights beautifully
There’s a lot to learn about the optical construction of this lens. Starting with the apodization element, this is inserted next to the diaphragm, and designed to transmit all of the light that’s directed through the centre of the aperture, but reduce its intensity gradually towards the periphery. In layman’s terms, the apodization element resembles a circular graduated ND filter that becomes darker towards the outer edge – and it’s this graduation that’s said to help produce smooth tonal transitions and creamy defocused backgrounds. The lens is also interesting in the way it has two separate diaphragms, both of which are controlled manually via separate rings on the barrel.
The 14-bladed circular aperture, which is located closest to the front of the lens, provides users with the ability to produce the smoothest bokeh possible. With its de-clicked aperture ring, it can actually provide videographers with a silent way of controlling the light passing through the lens, and the transmission value (the amount of light that reaches the sensor) is marked in T stops from T3.2 to T8. The eight-bladed aperture that’s located behind the 14-blade circular aperture is intended for photographers to control the aperture opening (f-number) and the depth of field in the usual way. However, this ring does click between stops. Note that when either one or the other diaphragm is used, the unused one should always be left wide open. For example, if the 14-blade circular aperture is set to f/5.6 or f/8, the eight-blade aperture should be set to f/2. Likewise, if the eight-bladed aperture is set to f/11, the 14-blade circular aperture should be set to T3.2.
Aperture control aside, the lens arranges 11 elements in eight groups and includes one HR (High Refractive Index) element, three LD (Low Dispersion) elements as well as two floating elements, not forgetting the apodization element. With a complex internal construction, it’s a heavy lens for its size and weighs 745g on the scales. Other features to note include its 90cm minimum focusing distance and its 67mm thread for attaching screw-in filters and adapters. It’s currently available for Canon EF, Nikon F, Pentax K and Sony A-mount DSLRs, as well as Sony E-mount CSCs, including the Alpha 7 series, and is priced at £649.
