Friday, February 15, 2013

An Overview of the Canon L Series Lenses

The "L" lens series is a line of professional lenses for Canon's EOS EF auto focus 35mm SLR and DSLR cameras.  Due to their innovative optical technology and sturdy construction, Canon's L series lenses are popular with both professional photographers and high-end amateurs alike.  Although Canon has not officially defined the "L" designation, there are two prominent explanations as to the meaning behind the "L" name.  It is speculated that "L" stands for either "low dispersion" due to the UD (ultra-low dispersion) glass used in the construction of the lenses, or "luxury" as referenced in Canon's Lens Work III Book.  No matter which way you choose to interpret the "L" designation, both popular definitions are valid in their own right.  Canon utilizes "low dispersion" optical technology in all of their L series lenses, and the high price and noted quality of the L lenses lend themselves to the "luxury" definition.

Canon produces the L series line for both zoom and fixed focal length lenses.   The L lenses will also work on all film and digital Canon EOS cameras.  The red ring around the end of the lens barrel identifies all Canon L series lenses.  Some of the lenses have a black finish, but the majority of the telephoto and super telephoto L lenses come in Canon's famous white finish (take a look at the gear of the professional photographers the next time you watch a major sporting event and you will be sure to see many white Canon L lenses).

Canon 300mm L Lens w/ Signature Red Ring & White Finish

Canon incorporates a combination of optical innovation and technology with rugged design in the production of their L series lenses to differentiate them from other lenses.  Canon L lenses also feature wider maximum apertures than other lenses, as this is highly desirable for photographers shooting in low lighting conditions.  This combination of factors is the basis behind the high-end quality and reputation of the L series lenses.  For instance, Canon uses fluorite crystals in many of the L series lens elements.  Fluorite is a great material for photographic lens elements because it transmits UV (ultraviolet) and IR (infrared) light well, has a low index of refraction and has a low rate of dispersion.

Having a low index of refraction is desirable because the less the light refracts (or bends), the sharper the focus.  The sharpness of an image is also affected by the convergence of light through glass because it breaks the light into colors with different focus points.  This is known as chromatic aberration, and using a fluorite lens element helps to reduce this effect by allowing for a lower rate of light dispersion. 

Chromatic Aberration in a Normal Lens vs. a Fluorite Lens

Despite the benefits of using fluorite for the lens elements, it can be very cost restrictive due to the rarity and delicate nature of working with the material.  This is also one of the contributing factors for the high price of some of the Canon L series lenses.  To counteract the costly nature of using fluorite, Canon developed UD (ultra-low dispersion) and Super UD (ultra-low dispersion) glass.  It is much less cost restrictive using UD glass rather than fluorite to manufacture camera lenses.  Although not as optically superior as fluorite, UD glass is very similar in that it has a low rate of refraction and dispersion.  The performance of UD glass is better than normal optical glass, and much more cost effective than fluorite.

Canon's Super UD glass is optically superior to standard UD glass, and creates results similar to fluorite.  Super UD glass is used in many Canon L series lenses and in some instances, a combination of Super UD and fluorite is used to create several high performance lenses.  This optical technology is important because with the perpetual development of higher resolution digital cameras, the greater the demand for an optically superior lens.

Canon 24-70mm L Lens w/ Signature Red Ring & Black Finish

Another contributing factor in the optical innovation of Canon's L series lenses is the use of aspherical lens elements.  Aspherical lens elements are critical in producing sharp images because of the curved nature of a spherical lens.  Spherical aberration occurs when light passes through glass and converges at different focus points.  Eliminating the curve of a spherical lens element allows for light to converge into a single point, thus resulting in a sharper image.

Spherical Aberration in a Normal Lens vs. an Aspherical Lens

In addition to optical performance, Canon employs the use of various coatings on the lens elements to achieve premium image quality.  SSC (Super Spectra Coating) is multi-layered coatings created by Canon to reduce lens flare and to faithfully reproduce color balance.  SWC (Subwavelength Structure Coating) is an anti-reflective coating that serves to reduce lens flare.  Canon L lenses also have a fluorine coating on top of the anti-reflective coating to aid in the removal of dirt from the lens.  The fluorine coating technology works to repel oil and water from the lens, resulting in the elimination of using a cleaning solvent.  The special nature of the coating also creates a smooth lens surface, thus preventing scratches.

Robust construction is yet another important factor in the quality of the Canon L series lenses.  It is extremely critical for photographers to have a lens that can withstand adverse shooting conditions such as rain, wind, dust, dirt, and other environmental challenges.  Canon utilizes rubber sealing at interface areas and on moving parts to protect against dust and moisture.  Canon's L series telephoto and super telephoto lenses also feature a white finish, which aids in the prevention of heat inside the lens.  The white lens surface reflects the sun, thus helping to keep the lens cool in warmer temperatures.

Canon L Lens w/ Rubber Sealing

So what does this mean for the consumer?  Superior optical performance and rugged lens construction are necessary for the work of a professional photographer.  The optical technology of the lenses aids in the delivery of high quality images with great color, contrast, and sharpness.  Canon's L series lenses also meet the demanding requirements of rigorous shooting conditions so the photographer can focus on capturing the subject matter at hand, rather than worrying about performance of the equipment.

To shop KEH's selection of Canon L lenses, click HERE.

For more information on Canon L lenses, check out the following websites:
* Canon Camera Museum  
* Canon Professional Network Infobank
~L.M.

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