Sigma Lens Glossary

Sigma Logo

APO (APO Lens) At Sigma Special Low Dispersion (SLD) glass becomes labeled as an APO lens. While the glasses refractive index is dependent upon the light's wavelength, color aberration happens when different colors develop images at unique points. This issue often happens with telephoto lenses. When using normal optical glass, correction can only be for two spectral primary colors by combining convex low dispersion and concave high dispersion lenses. All Sigma Apo lenses employ (SLD or the new Extraordinary Low Dispersion (ELD) glass to provide superior sharpness, elevated Contrast and color adjustment by minimizing any chromatic aberration..

APO Macro Super - Although telephoto zoom lenses can be used closer to the object than single-focal length telephotolenses, there is still a minimum shooting distance. SIGMA has made this minimum distance smaller and developed the zoom MACRO lens for taking close-up photographs of the same quality as those taken with a regular MACRO lens, while maintaining the performance specific to an APO lens. Rather than carrying around the cumbersome accessories required for close-up work, the photographer can now take photographs at a magnification of 1:2 (one half lifesize) using a telephoto lens, by quickly shifting from the normal setting to the full macro setting.

 ASP (Aspherical Lens) The aspherical lens complex allows freedom of design, improved performance, a reduced number of component lenses and a compact size. This lens provides high optical performance while maintaining a compact size. For example, the 12-24 mm F4.5-5.6 EX DG ASPHERICAL lens widens the range of wide-angle lenses, and it provides distortion-free images with image reproduction performance equivalent to that of a single focal length lens. Aspherical lenses allow the production of high-quality images from compact, lightweight telephoto zoom lenses.

Conv (APO Teleconverter EX)This lens can be used with the APO Teleconverter EX. It can increase the focal length and will interface with the camera's AE (automatic exposure) function.

 DC (DC Lens)
These are special lenses designed so that the image circle matches the smaller size of the image sensor of most digital SLR cameras. Their specialized design gives these lenses the ideal properties for digital cameras, the compact and lightweight construction is an added bonus!  These lenses will not give a full image on 'full frame' cameras.

DF - Dual Focus System.
The DF system disengages the linkage between the internal focusing mechanism and outer focusing ring when the focusing ring is moved to the AF position. This system provides easy and precise handling of the lens, since the focusing ring does not rotate during autofocusing. The wide focusing ring also enables easy and accurate manual focusing.

 DG (DG Lens)
The DG designation indicates that the lens has been optimized for use with digital SLR cameras. These are large-aperture lenses with wide angles and short minimum focusing distances. With an abundance of peripheral illumination, they are ideal lenses for Digital SLR Cameras while retaining suitability for traditional 35mm SLRs. DG lenses are designed to work on 35mm film cameras and digital cameras with 'full frame sensors. They can also be used on the cropped sensor Cameras mentioned above because the image circle they cast on the sensor is larger than needed.

The DG lenses feature improved (more even) light distribution from image centre to edge, especially at maximum aperture, compared to conventional fast wide-angle lenses. This is important in digital photography, but is also useful in 35mm photography, especially when slide film is used. The lens elements also utilize Sigma’s super multi layer coating which reduces flare and internal reflections from the highly sensitive surface of image sensors.

The improved DG lens design corrects for various aberrations. This macro lens is specially coated to get the best color balance whilst cutting down on ghosting caused by reflections from the digital image sensor. The lens provides the utmost correction against lateral chromatic aberration which is a serious problem for digital SLR cameras.

DL - DeLuxe.
This refers to Sigma lenses having this designation, which are supplied with a number of features and accessories, such as: a custom lens hood, DOF scale, distance scale, infrared correction mark, etc. Sigma says, "One or more of these features are usually missing from comparable lenses of similar price from other manufacturers, so the lens is considered DeLuxe".

EX (EX Lens)
The exterior of this lens is EX-finished to denote the superior build and optical quality, and to enhance its appearance. High performance

FLD glass is the highest level low dispersion glass available with extremely high light transmission. This optical glass has a performance equal to fluorite glass which has a low refractive index and low dispersion compared to current optical glass. It also benefits from high anomalous dispersion. Using these characteristics gives excellent correction for residual chromatic aberration (secondary spectrum) which cannot be corrected by ordinary optical glass and ensures high definition and high contrast images. FLD glass offers superior optical performance, equal to fluorite, at an affordable price. The density of FLD glass is lower than traditional optical glass, ensuring a lighter construction of large aperture lenses.

FLD glass has been incorporated into some of our recently announced lenses; 4 elements have been included in the Sigma 8-16mm F4.5-5.6 DC HSM as well as 2 elements in both the Sigma APO 70-200mm F2.8 EX DG OS HSM and the Sigma 17-50mm F2.8 EX DC OS HSM.

Floating System
The floating system is used to control the focus. This system moves the different lens groups in the optical system to different positions, thereby minimizing the telescoping distance and the fluctuation of aberration at different shooting distances. This system is particularly effective for macro lenses (which encompass a wide range of shooting distances) and wide angle lenses (for Single-Lens Reflex cameras) whose lens composition is asymmetric. SIGMA uses the floating system for the MACRO 50 mm F2.8EX DG lens and the large-aperture wide-angle 28 mm F1.8 EX DG ASPHERICAL MACRO lenses.

G- This lens (similar to Nikon "G" type lenses) does not have an aperture ring on the lens, and is not fully compatible with the F4, N90-series, N70, N8008-series and N6006 (or older model) cameras. With these cameras, only programmed auto or shutter-priority auto exposure mode can be used.

HF — "Helical Focusing", front element of lens does not rotate (useful for polarizing filters and petal lens hoods)Helical Focus. Eliminates front lens rotation, allowing the use of a perfect hood and easy to use polarising filters.

HSM (Hyper-Sonic Motor)
Sigma HyperSonic MotorThis lens uses a motor driven by ultrasonic waves to provide a quiet, highspeed AF. With conventional auto-focusing, auto-focus is driven by electromagnetic force of a DC-motor, gear and shaft mechanism. However, Ultrasonic Oscillation Energy operates the HSM lens and creates high-torque drive. Since this motor has no reduction gears, it has much quicker response to start and stop compared to DC- motor lenses. HSM system has virtually silent auto focus function, very quick responsive auto focus function and "full-time" manual focus, wherein a lens incorporating HSM is capable of autofocusing at high speed and low noise, and can also be used in full-time manual focusing operation with which fine focus adjustment is possible by simply turning the focusing ring after approximate focus has been obtained with autofocusing.This lens will autofocus on Nikon D40/D40x, Nikon D60, Nikon D3000, Nikon D3100 and the Nikon D5000

IF (Inner Focus)
To ensure stability in focusing, this lens moves the inner lens group or groups without changing the lens' physical length.

OS (Optical Stabilizer) Function
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.

Developed with Sigma's own technology, the OS (Optical Stabilizer) function uses two sensors inside the lens to detect both vertical and horizontal movement of the camera. This function, which works by moving an optical image stabilizing lens group, to effectively compensate for camera shake, helps to set our lenses apart from the rest. To handle all types of shooting conditions, the system has two optical stabilizer modes. Mode 1 determines camera shake in vertical and horizontal panning and compensates for image blurring. It is therefore effective for taking general photography or for shooting landscapes and other static subjects. Mode 2 detects vertical camera shake and compensates for blurring. It is effective for panning the camera to photograph moving subjects such as motor sports.

RD- Rounded Diaphragm
Soft-focus images of point light resources create accepted polygonal shapes that mirror the form of the cavity produced by the diaphragm blades. The rounded diaphragm employs blades designed to produce a circular style opening for an added lovely soft-focus result

RF (Rear Focus)
This lens is equipped with a system that moves the rear lens group for high speed , silent focusing.

Conventional focusing has normally been performed by moving either all lens groups as a fixed unit or only the first lens group. AF cameras are now widely used, even for close-up photography. Consequently, demand has arisen for a focusing system that will keep the length of the lens unchanged while showing little fluctuation of aberration. In response to this demand, SIGMA has developed a new inner focus system that moves two lens groups inside the telephoto and telephoto MACRO lenses. This system has floating elements that substantially improve the close-up capability of the lens. The super wide angle lens having a large front-lens uses a rear focusing system to move the rear-lens apparatus and enhance the floating effect, and the18-125 mm F3.5- 5.6 DC lens uses an inner focusing system to move the secondary lens apparatus. SIGMA has also succeeded in attaining a minimum shooting distance of 19.7 inches/0.5 m throughout the entire zoom range of this lens. The rear focus system ensures high-speed focusing with the APO 135-400 mm F4.5-5.6 DG and APO 170-500 mm F5-6.3 DG telephoto zoom lenses.

SLD - Special Low Dispersion -  glass elements provide excellent correction of all types of aberrations and the Super Multi-Layer Coating reduces flare and ghosting. This lens has superior peripheral brightness and provides sharp, high contrast images even at the maximum apertures.

The Super Multi-Layer Coating reduces flare and ghosting and provides high contrast images throughout the focal range.

Tele-macro mechanism lets you select a magnification of up to 1:2 at the telephoto end simply by engaging a switch. With a minimum shooting distance of 19.7 inches (50 cm) over the entire zoom range, turning on the Macro switch at the telephoto end allows the focus ring to enter the macro range,allowing close-up photography. Since close-up photography with a magnification of up to 1:2 is possible without attaching a close-up lens or changing to a macro lens, this mechanism gives you extra versatility in photography. When the Macro switch is engaged, the zoom control ring is fixed at the telephoto end.

UC - Ultra Compact - which is more or less equivalent with ultra crappy build quality

Zoom Macro
Although telephoto zoom lenses can be used closer to the object than single-focal length telephoto lenses, there is still a minimum shooting distance. SIGMA has made this minimum distance smaller and developed the zoom MACRO lens for taking close-up photographs of the same quality as those taken with a regular MACRO lens, while maintaining the performance specific to an APO lens. Rather than carrying around the cumbersome accessories required for close-up work, the photographer can now take photographs at a magnification of 1:2 (one half life size) using a telephoto lens, by quickly shifting from the normal setting to the full macro setting.


Corresponding AF Mounts: "o"=available,"-"=not available, S=Sigma; SO= Sony/Konica-Minolta; N=Nikon; P=Pentax AF; C=Canon EOS, FT=Four Thirds mount, G=G type Nikon mount lens (There is no aperture ring on the G-type lenses), D=Distance Information Function for Minolta or Nikon, J=J type Pentax AF mount lens (There is no aperture ring on the J-type lenses), HSM=Hyper Sonic Motor AF drive