DG Lens - These are high-performance lenses optimized for digital cameras. They are ideal not only for 35 mm digital SLR cameras and film SLR cameras but also for APS-C digital SLR cameras. They deliver superior image quality by correcting for all types of aberration, especially distortion, and they have high resolution capability because they minimize chromatic aberration of magnification, which is particularly a problem for digital cameras. What is more, these lenses incorporate optical designs optimized for digital cameras and Sigma's own Super Multi-Layer Coating technology, so they reduce flare and ghosting due to reflection between the image sensor and lens surfaces, and they provide high contrast and a wide range of tone. They also provide enough peripheral brightness with little vignetting.

APO Lens - In order to attain the highest quality images, the APO lens has been made using special low-dispersion (SLD) glass and is designed to minimize color aberration. SIGMA's APO zoom lenses minimizecolor aberration. As the refractiveindex of glass depends on thewavelength of light,color aberrationoccurs when different colors formimages at different points. Thisproblem often occurs with telephotolenses,but the Special Low-Dispersion(SLD) glass and Extraordinary LowDispersion (ELD) used in SIGMA'sAPO lenses helps to compensate forcolor aberration, thereby allowingthem to produce of sharp images.

Hyper Sonic Motor (HSM) - HSM lenses are equipped with a motor driven by ultrasonic waves. The motor makes high AF speeds and quiet shooting a reality.

Rear Socus (RF) - This lens is equipped with a system that moves the rear lens group for highspeed , silent focusing. Conventional focusing has normallybeen performed by moving either all lens groups as a fixed unit or onlythe first lens group. AF cameras are now widely used, even for close-upphotography. Consequently, demand has arisen for a focusing system thatwill keep the length of the lens unchanged while showing little fluctuationof aberration. In response to this demand, SIGMA has developed a newinner focus system that moves two lens groups inside the telephoto andtelephoto MACRO lenses. This system has floating elements thatsubstantially improve the close-upcapability of the lens. The superwide angle lens having a large front-lens uses a rear focusing system tomove the rear-lens apparatus andenhance the floating effect, and the18-200mm F3.5-6.3 DC features aninner focusing system to move thesecondary lens group duringfocusing. This lens has a minimumfocusing distance of 45 cm / 17.7inch throughout entire zoom range.The rear focus system ensures high-speed focusing with the wide lens20mm F1.8 EX DG ASPHERICAL RF.

Optical Stabilizer (OS) - This function utilizes a built-in mechanism that compensates for camera shake. It dramatically expands photographic possibilities by alleviating camera movement when shooting by hand held camera. The OS function uses two sensors inside the lens to detect vertical andhorizontal movement of the camera and works by moving an optical imagestabilizing lens group to effectively compensate for camera shake. The OSfunction offers the equivalent of using a shutter speed 4 stops faster makingit suitable for telephoto and low lightphotography. As the stabilizing feature is built intothe lens, it can be designedspecifically to suit the characteristicsof that lens. This provides precisecompensation for camera shakethroughout the entire zoom range.This also enables the correctlystabilized image to appear in theviewfinder aiding autofocus andcomposition.

Teleconverter-Compatible Lens (CONV) - The "CONV" mark designates lenses that can be used with the APO Teleconverter EX (sold separately). The teleconverter increases the focal length and interfaces with the AE (automatic exposure) function of the lens.