Canon Lens Glossary


All older Canon EF lens versions function with the present DSLR cameras including, of course, the operational change in coverage when using the lenses with image sensors that are smaller than 35mm SLR size (i.e. APS-C). Even those old Canon FD lenses are able to be mounted, by using an FD-EOS Lens Converter Mount.

The EOS FD Macro Lens Converter Mount was available from Canon dealers and it worked with all FD camera lenses and accessories, although it functioned only with macro use. This mount was subsequently discontinued but you might still find it in the used marketplace.

The original EOS FD Lens Converter Mount included an extender that multiplied the actual focal length of the lens by a 1.26x factor , although it was only suitable for the majority of FD lenses with focal lengths longer than 200mm. This limitation was a consequence of a front element that protrudied on the tele-extender of the converter, that interfered with the shorter lens focal-lengths. This last converter was not available through dealers but only offered to members of a program for Canon Professional Services. When using either converter with an old FD lens on newer Canon DSLR cameras requires the lens to be manually stopped down since the operation of the diaphragm is only manual with no autofocus verification. When using either converter with any older FD lens, two basic options exist to control exposure; Manual mode by setting the speed of the shutter and then manually stopping the lens down or use stop down autoexposure when you stop the lens down and the camera automatically sets the shutter speed.

"II" or "III Series lenses are later versions of a particular lens, eg. EF 50mm /1.8 II. is a newer version of the EF 50mm/1.8 lens. It is also made of less expensive materials than the original model, but is still rated as being quite sharp for the cost of the lens.

AFD - Arc-form drive (AFD). Generally used in a number of older lower-cost lenses, AFD motors are simply little electric motors which drive a geartrain. Theyíre somewhat noisy - electric buzzing and grinding of gears - and not terribly fast. This isnít a big deal on smaller lenses since the distances the motors must move the focussing elements isnít very far. However, telephoto lenses with AFD motors can be quite sluggish.

AL - Aspheric Lens, used to minimize aberrations. Aspherical lenses incorporating some optical characteristics. These lenses are small, lighter and in general, better than similar lenses which only employ spherical elements. In some instances, using an aspherical element enable the lens designer to use fewer lens elements. The benefit can be a smaller, compact and lighter lens; with fewer lens surfaces, there is also less potential for internal reflection - that is why there are more and more zoom lenses incorporating a (or few) aspherical lens element within to substitute a number

CA - normally Chromatic Aberration, but Canon also use this abbreviation for Circular Aperture lenses (lenses with multiple aperture blades shaped to give as circular an iris shape as possible).

CaF2 - Fluorite element (even more effective than super UD for correcting chromatic aberration). Used in most Super-telephoto lenses.

Compatible with Canon EF and EF-S Lenses
Compatible with all Canon lenses in the EF and EF-S lineup, ranging from ultra-wide angle to super telephoto lenses. Canon lenses employ advanced optical expertise and micron-precision engineering to deliver unprecedented performance in all facets of the photographic process. Special optical technologies, such as aspherical, ultra-low dispersion, or fluorite elements are featured in the universally acclaimed L-series lenses. And Canon's Optical Image Stabilizer technology is featured in select lenses to minimize the effect of camera shake. Additionally, photographers can use for video the same lenses they do for still photography; Canon wide-angle, macro, super-telephoto, tilt-shift and fisheye lenses provide a wealth of focal lengths, depth-of-field and other creative shooting options once reserved for stills

18MP CMOS Sensor and DIGIC 4 Imaging Processor The Canon-designed 18MP APS-C size CMOS sensor captures such a high level of resolution, it's easy to crop images for enlargement without concern of losing detail. A major factor in reducing noise, the CMOS sensor assures that images shot at highest sensitivity will be remarkably smooth The improved DIGIC 4 Image Processor ensures that images are captured, processed and saved with remarkable speed. The 3:2 multiple aspect ratio, in-camera RAW image processing, creative filters, image resizing and provided S2 and S3 image-recording quality are all possible thanks to the DIGIC 4 Image Processor. With dazzling results, the new DIGIC 4 Image Processor also works to capture and process data of images shot at 18MP at 5.3 fps, as well as 14-bit signal processing for excellent image gradation, enhanced Face Detection Live mode, Full HD video recording, Auto Lighting Optimizer and Lens Peripheral Optimization

DO - Diffractive Optics, Multi layer diffractive optics is relatively new technology. At present there are only two lenses in the range that feature this technology. This revolutionary technology is unique to Canon and allows lenses to be made shorter and lighter than would be possible with conventional lens technologies. The performance of these lenses is outstanding and the lenses have a special lens coatings optimized to minimize the ghosting and flare that can be associated with this new technology. In most shooting situations they are superb but if you shoot a lot with backlighting or rim-lighting then flare can be an issue. This is just a different way of making lenses which uses fresnel technology.

EF - "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens. All communication between camera and lens takes place through electrical contacts; there are no mechanical levers or plungers. These are Canon lenses that will fit on any Canon EOS body. All EOS cameras have the EF mount and it is indicated on the lens and body mount by a red dot. Stands for electronic focus. The EF lens mount allows all the Canon EF lenses to be used on any of the Canon EOS line of cameras made by Canon Inc.

EF-S lens mount - A derivative of the EF lens mount created for a subset of Canon digital single-lens reflex cameras with APS-C sized image sensors. It was released in 2003. Cameras supporting the EF-S mount are backward-compatible with the EF lens mount. Only Canon cameras with the APS-C sized sensor released after 2003 support the mount. All other cameras do not support it. In 2003, Canon introduced the EF-S lens mount, a derivative of the EF mount that is strictly for digital EOS cameras with a 1.6x crop released after 2003. All other EOS cameras that only have an EF mount will not mount EF-S lenses.

E-M - Electronic manual focusing (used on some older USM lenses where manual focusing was done electrically via the USM motor).

EMD - Electro-Magnetic Diaphragm. All Canon EOS lenses use an electrically controlled aperture.

EOS - Electro Optic System. - The Canon EOS (Electro-Optical System) autofocus 35 mm film and digital SLR camera system was introduced in 1987 with the Canon EOS 650 and is still in production as Canon's current dSLR system. The acronym EOS was chosen for Eos, the Titan Goddess of dawn in Greek mythology, and is often pronounced as a word (i.e., EE-oss), although some spell out the letters. There is no officially correct pronunciation, as both seem logical.

EOS HD Video
The EOS HD Video capture technologies - manual exposure control for more creative control, for example - borrowed directly from professional Canon DSLRs to capture stellar video with all the benefits of shooting with a DSLR. By shooting video, photographers as well as filmmakers can take advantage of the creative features native to DSLR cameras. Along with its manual controls, allows for full use of Canon EF and EF-S lenses, including Macro and Fisheye, providing a plethora of shooting options once reserved only for still photography. The resulting HD video is a standout in its beautiful depth-of-field characteristics and remarkable capture capability under poor lighting conditions. Additionally, a Movie Crop function is included: An SD-quality video (640 x 480) can be cropped to the equivalent of about 7x magnification of regular shooting

The audio input level can be set to auto or manual, up to 64 levels, and a wind filter minimizes unwanted background noise. By pressing the Quick Control button, a simple graphic user interface for adjusting image quality, white balance, image creation and other settings appears on the LCD. The EOS 60D even lets users edit video in-camera: On-site or off, unnecessary scenes can be deleted and the start/end points of video footage can be designated via in-camera editing functions without the need of a separate computer

Video can be captured at a number of resolutions and frame rates for numerous applications. It can capture 1920 x 1080 Full HD video at frame rates of 30 (29.97 fps), 24 (23.976 fps) and 25.0 frames per second, for up to 4GB per clip. Video footage is saved as MOV files and can be viewed in Full HD through the EOS 60D DSLR's HDMI output. Other recording sizes include HD at 1280 x 720 (50/60 fps) or SD/VGA at 640 x 480 (50/60 fps) -24/30 fps delivers cinema-like motion, while 60 fps is perfect for footage being uploaded to video-sharing websites. The EOS 60D also has a built-in microphone for simple mono recording and stereo sound can be recorded through a self-powered external microphone

Flash Photography
With a flash sync speed of 1/250 of a second, the E-TTL II flash metering system. With any of the optional flashes in the EX Speedlite line, E-TTL II provides reliable flash output whether shooting fill-in flash pictures in sunlight, or using flash in total darkness. With E-TTL II, the exact same 35-zone metering sensor used for measuring ambient light is also used for flash metering - giving even finer metering command of the image area. If you prefer a broader area for flash metering, there's a menu setting to change to "Average" flash metering - where the entire 35-zone area is measured evenly for flash exposure. Additionally, the Speedlite transmitter is built-in for convenient, full-featured wireless control of EX-series Speedlite flashes set as slave units The optional Canon Speedlite 430EX II is a step-up accessory for powerful flash shooting. It has excellent flash power (maximum guide number of 141 ft./43m at ISO 100), and is the perfect way to get great flash pictures when you can't get right up to the subject. The 430EX II is also great for bounce flash, with its tilting and swiveling flash head. It automatically zooms the flash head to cover lenses ranging from 16mm up to 105mm or longer. Of course, it works with the camera to provide full E-TTL II automatic flash exposure. And the 430EX II has a powerful AF-assist beam, which allows the camera to autofocus even in total darkness on subjects as far as 32 ft. from the camera

Float - Floating elements which move to correct aberrations when close focusing. Nikon call this CRC (Close Range Correction).

FF - Full-frame Canon CMOS sensor - A full frame digital camera is equipped with the full frame CCD which is the simplest form of sensor in which incoming photons fall on the full light sensitive sensor array. To readout the sensor the accumulated charge must then be shifted vertically row by row into the serial output register and for each row the readout register must be shifted horizontally to readout each individual pixel.

FP - Focus Preset. A single focus distance can be preset and instantly returned to. This is available on some super telephoto lenses.

FR - Filter rotation, front element rotates during focusing.

FS - Focus Range Selector. Some lenses can restrict focus range for faster operation

FT-M - Full time manual focus. Manual focus is possible even with lens in AF mode.

G-E - Groups/Elements. How the individual lens elements are arranged within the lens.

GMO - Glass-molded (aspheric) Optics, less expensive than ground and polished aspheric.

High ISO Sensitivity
With a wide range of ISO settings, expandable up to 6400 in automatic mode, and 12800 with custom function that allows shooting from sunrise to sunset and helps ensure the collection of the finest details . Optimization with improved high sensitivity, subjects can be captured clearly and easily at high shutter speeds without flash, with a minimal blur and noise. In bright scenes, especially for long exposures in daylight, optimal exposure is obtained with a large diameter lens fully open, no need to use a filter

I/R - Internal or Rear group focusing (lens length does not normally change during focusing, front element does not normally rotate).

IS - Image Stabilization, Image stabilization was another system pioneered onto the market by Canon. Today this has become a standard technology with lots of manufacturers now featuring a similar technology. The Canon system actually is very simple in how it works and having the image stabilization in the lens rather than in the body still offers significant advantages as it can be custom made for what the lens really needs. This system is designed to counter hand or other movement that would result in camera shake. It allows lenses to be used depending on the lens in use 2, 3 or even 4 stops slower than would normally be possible. However it needs to be remembered that if a certain shutter speed is needed to freeze action then having IS in the lens will not help freeze the subjects' movement. It is however very beneficial for photographers who have to pan a lot making the subject easier to follow and allowing panning at shutter speeds much slower than could have been successfully used in the past.

L - This indicates that the lens is a professional L series lens. Take it for granted that along with the letter L comes a high price tag as these lenses are made to the ultimate quality and offer the very best in performance. They also offer the ultimate in terms of focusing performance. Just like the GT-i badge on cars and the lenses even have a nice red strip to indicate what they are! Generally the lenses contain special technologies that give them the increased performance and these include Aspherical elements, Flourite glass, UD or ultra low dispersion glass and super UD elements, though many great lenses from Canon are not L.

Flourite and LD/UD Glass, The refraction of light differs depending on the wavelength. The point of focus therefore differs depending on the different wavelengths or colors. When the different wavelengths are focused at different points, the colors look smeared. This is called chromatic aberration. The longer the focal length, the more pronounced chromatic aberration becomes. Usually, an achromatic element is used in a lens to correct chromatic aberration. However, normal optical glass can only be corrected for two primary spectral colors. An exception to this limitation is Fluorite, an ideal material. Fluorite, which is crystalline, has abnormally low refraction and dispersion characteristics, which optical glass cannot achieve. It also has anomalous dispersion from the green to blue wavelengths. Canon developed production technologies to manufacture fluorite. By incorporating Fluorite in lenses, the points of focus of the three primary spectral colors of red, green and blue all meet at one point for ideal correction of chromatic aberration. There is also UD-glass, which is a special type of optical glass whose properties nearly match those of Fluorite. The effect of two UD-glass elements gives almost the same effect as one Fluorite element. And one super-UD-glass element gives almost the same effect as one Fluorite element. (LD glass) is a type of glass with low dispersion glass elements. Its chief use is in lenses, where SLD elements minimize the chromatic aberration of the lens assembly. 

Macro lenses
A macro lens enables you to fill the frame with very small objects. The true definition of macro is photography at 1:1 or 1x magnifications. In other word the subject will be the same size on the sensor when captured as it is in life. Although many zoom lenses have a "macro or close up feature" they do not offer 1:1 magnification. This can only be achieved through the use of a specific macro lens.

MM - Micro Motor focusing motor. Slower and noisier then USM.
The mm indicated that the number it is after is the focal length of the lens. So 28mm indicates it is a 28mm lens which is generally known as a wide angle lens. 17-85mm indicates that it is a zoom lens with focal lengths between 17mm and 85mm. The lower the number the wider the lenses angle of view, the higher the number the narrower the angle of view becomes making the lens magnify the subject more making it appear closer. Numbers lower than 50mm are wide angle lenses and numbers higher than 50mm are telephoto lenses.

MTF - Modulation Transfer Function. A measure of the lens sharpness (higher is better).

SF - Soft Focus. The 135/2.8 SF is the only current Canon soft focus lens.

ē Super Spectra coatings
Canonís Super Spectra lens coating is used to prevent flare and ghosting. These are more prone to occur with digital cameras due to reflection off the image sensor. The use of optimized lens coatings prevent flare and ghosting and ensure excellent color balance and contrast.

Super UD - Super ultra low dispersion glass (even more effective than UD for correction of chromatic aberration)

T/S or sometimes TS-E - Canon's designation for tilt and shift lenses. These allow the lens to be tilted at an angle from the camera and to be shifted to allow perspective controls to be performed in camera rather than in the post production stages. They also can allow the depth of field in a scene to be manipulated. They take experience to understand and use correctly and are really only fully effective on the full frame or 1x chip models. They are mainly used in architectural photography but they also have their used in a commercial studio environment.

UD - Ultra-low dispersion glass used to correct chromatic aberration

USM - Ultrasonic Motor, specific to Canon models. Sigma calls it's version HSM (high speed motor?).This indicates that the lens is fitted with an USM or ultrasonic motors. This is technology that Canon pioneered and allows the lens to respond and focus incredibly fast due to the way it works. Today this technology is still very special and is one of the key reasons why the Canon focusing system is always held up as the very best available today.

Vari-Angle 3" Clear View LCD Monitor
The a bright, high resolution, flip-out Vari-angle 3.0-inch Clear View LCD monitor for shooting at a variety of angles. By easily switching between low and high angles, the vari-angle freely enables angle adjustments even if the camera is mounted on a tripod or has a battery grip attached

Wide angle
A lens that has a wide field of view. Wide angle lenses make things look further away than they are in reality and as a result thing will appear smaller on the image than they are to the naked eye. Lenses below 35mm are generally referred to as wide angle and lenses wider than 17mm as ultra wide