FLD ("F" Low Dispersion) glass using the highest level of low dispersion glass with high light transmission. Performance of the FLD with flourite glass which has a refractive index of low character and low dispersion. FLD glass offers superior optical performance, equivalent to flourite, and of course, at an affordable price
ELD (Extraordinary Low Dispersion) glass has a lower dispersion characteristics than SLD (Special Low Dispersion) glass. Sigma Lens APO to make use of (used also for some non APO Lens)
Reason code "DG" on Sigma Lens
Sigma DG lenses are used in the new version, which shows these special lenses for DSLR Camera. The increase in the distribution of light from the image center to the edge, using a multi-layer lens coating to prevent reflection from the camera sensor.
Where Sigma product (Lenses, Camera and Flash) made?
All products are made in factories in Sigma Aizu, Japan. None of the products of Sigma made outside the above mentioned plant.
APO Lens
Apochromatic are telephoto and telezoom lens type, that uses a special optical design and material (SLD or eld Glass) to improve performance. The result, the level of contrast, sharpness and better color.
Aspherical lenses
Many of the Sigma lens make used of elements Aspherical lens. This technology allows an aspherical element to perform the functions of two or more confessional spherical elements, therefore, the lens can be made more compact and lighter, without losing performance. Example: 20mm lens at f/1.8, 24mm f/1.8, 28mm f/1.8 EX DG, Aspherical elements eliminate the sagittal coma flare which is common in large diameter lens. At wide angle zoom lens, such as the 15-30 f/3.5-4.5 EX DG lens - the distortion can be corrected by using Aspherical elements.
Meaning of HSM in Sigma lenses
HSM (Hyper Sonic Motor). Type motors used Sigma lenses new output. Pros: smoother autofocus, autofocus is fast response.
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