What is it
L-lenses can be recognized by a red ring around the front part of the lens. Most recent L lenses have sealing to help resist dust and water. L-lenses are typically used by professionals and serious amateurs due to their high price and large mass.
Most L series lenses share a number of common characteristics:
- Tough build, made to withstand trials in the field (some incorporating dust and moisture resistant rubber seals).
- At least one fluorite or ultra-low dispersion glass element, combined with super-low dispersion glass and ground aspherical elements.
- Non-rotating front elements, which are optimal for some filters (e.g. circular polarizers).
- Relatively large apertures compared to other Canon lenses in the same focal lengths.
- Ring-type USM (ultrasonic motor) and full-time manual focusing.
- Three additional data communication pins on Canon Extender EF compatible lenses, compared to the standard EF mount.
There are some lenses which include one or more of these technologies but which are not designated L-lenses. L-lenses are often equipped with USM and/or IS, but optical performance is the key criterion.
Larger sized L-lenses, such as the 70-200 mm and 100-400 mm zooms and longer focal length primes (300 mm+), usually have an off-white barrel (sometimes referred to as the color “putty”) to reduce heat absorption under the sun that may otherwise affect the performance of the lens, as well as to identify Canon’s lenses (for example at sporting events). However, shorter focal length L-lenses can be black (such as the Canon EF 24-70 mm f/2.8L and all L-lens primes under 300 mm, with the exception of the discontinued 200 mm f/1.8L and newly announced 200 mm f/2.0L IS.). Therefore L-lenses can be identified by either a lens barrel’s off-white colour or, as on all L-lenses, the distinctive red ring on the lens barrel.
Wide angle L-lenses typically have a gelatin filter holder on the mounting point of the lens, which allows the photographer to cut a small, square piece of gelatin out of a larger filter sheet and place it on the lens. On film cameras, these are typically used to correct the color temperature, but on digital cameras this is largely unnecessary, as the color temperature can be corrected in software. The mount is still commonly used for neutral density gelatin sheets though, especially on certain wide-angle lenses where the protruding front element precludes the use of any screw-in filters. Some telephoto L-lenses, such as the EF 70-200mm zoom lenses, or the EF 300mm f/4L IS USM do not have rear gelatin filter holders. Super-telephoto lenses such as the EF 500mm f/4L IS USM, or the EF 200mm f/2L IS USM do have a rear 52mm drop-in filter holder, than can be used to hold gelatin type filters.
Is it worth the EXTRA COST
I do really think that the L glass is worth it, the image sharpness, quality, bokah, lower aberrations around the corners all are much better on the L glass lenses. Compared to some lenses, there is no question. Others, is it less noticeable. The 70-300 consumer glass version zoom can be VERY good and sharp. The newer 70-300L (a VERY expensive lens) is sharper, but mostly one gets a different form factor and four stops of image stabilization.
Another additional benefit of MOST L glass is weather proofing against water, dust, sand, etc. This can be VERY nice to have in such conditions. L zoom Lenses TEND to carry the same maximum aperture across the entire zoom range, which is nice to have. None of the consumer version will do that.
Another thing to note is that the L lenses hold their value much better. I tend to get equipment at about 10-15% off retail and then the lens will lose about another 10-15% value over time. The L glass can hold easily 65-75% of its value if well maintained and then sold through a photo forum or even ebay. Wereas most consumer version is at most 50%, or less.
You really have to assess if you need this extra quality. Working pro then yes, hobby, maybe not. These lenses with give superb results, in the right hands but if all you ever do is make 5 x 7 prints or small images for the web then a good generic consumer lens may be the better prospect. There are some excellent lenses produced not only by Canon but independents such as Sigma, Tamron and Tokina. Try before you buy.