Every company has its own feature branding. It is confusing keeping this straight within your favorite brand, let alone when looking at other brands. This applies to understanding common lens features when comparing OEM lenses of independent manufacturers. The following enumerates some of these key lens features and identify the branding letters.
I will focus on key OEM brands, Canon and Nikon, but may add information for other brands as I find them. I’ve chosen to cover the more popular independent lens companies, Sigma and Tamron, as well.
|Full-frame coverage lens||EF – Electrofocus||AF, AF-S, FX||Di||DG|
|Optical/mechanical image stabilization||IS – image stablilization||VR – vibration reduction||VC – vibration compensation||OS – optical stabilization|
|Internal focusing lens||IF||IF||IF|
|Quiet focusing motor||USM – Ultrasonic motor, STM||SWM||USD||HSM – Hyper Sonic Motor|
|Low dispersion||LD, HID||LD, ED, UD||LD, XLD, HID||SLD, ELD, FLD|
|Premium / Professional||L – Luxury (red ring)||(gold ring)||SP||EX|
Full-frame Coverage Lens
“Full-frame” can be a mis-understood term. It refers to the 36mm×24mm frame size of “35mm” film cameras, the form-factor from which contemporary dSLR cameras have derived. This is a large-size sensor and has many advantages over “crop-sensor” dSLRs. For full-frame sensor cameras, it is important that lenses can “cover” the its large sensor. If you are using crop-sensor cameras, you can continue to use these lenses, should you ever move to cameras will full-frame sensors. (see “Crop-sensor” below).
A more popular class of dSLR cameras contain a sensor which is 1/1.5 or 1/1.6 the size of a full-size sensor (usually). Because of the smaller size, lenses designed to cover this smaller area can be made cheaper and more compact. If the camera has a full-sized sensor, then crop-sensor-specific lenses will not cover the full area of the sensor. The lens may not even fit on a full-frame sensor camera. (See “Full-frame, above).
Optical/mechanical image stabilization
Hand and camera shake can be counteracted by optical or mechanical “image stabilization”. If not built into a camera, it can be integrated into a lens, itself.
Internal focusing lens
It can be beneficial for lenses to be as static as possible during its operation. Those with internal focusing operation do not alter their external size as they are focused (lenses within the lens are moved internally, only).
Quiet Focusing Motor
Quiet shooting is always a desired feature; a quiet auto-focusing motor helps with this. As video recording becomes a more commonly used feature of dSLRs, a quiet focusing motor becomes even more important, to avoid being heard in a recording.
These designations highlight the use of exotic glass materials to minimize chromatic aberration (which results in colorations due to colors naturally focusing differently). Different glasses perform differently but are usually accompanied with higher costs due to rarity, purity, and manufacturing complexities.
Tilt-shift lenses are specialized lenses that allow manual manipulation of the geometry of the lens in a fashion which mimics large-format, bellows lenses.
Premium / Professional
This is a branding indicator for a lens by the manufacturer, a short-hand way to identify that the lens is the best of their best. Notably, Nikon does not have a separate designation for their premium lenses, but identifies them with a gold-ring around the front of their premium lenses.
If you are a Nikon user, it is important to notice whether the camera requires lenses to have their own focus motor. If your camera does not have a focus motor and the lens doesn’t either then auto-focus will not work. In other words, if your camera does not have a auto-focus motor, then you must use an AF-S lens (which have a built-in motors). Tamron designates such lenses as BIM.
I hope this makes it a bit easier to understand lens designations and make sense of them as you compare various lens features. There are many other designations that I did not cover, but these are the most common and the features which might be most important in understanding the differentiations between lenses. Did I miss anything important? Let me know.