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ASPH, APO, OIS, WR, USM, GM, ED, VC, DG

We are used to seeing in the names of an optic, in addition to the focal length and aperture, a series of acronyms (also called acronyms) that we often fail to understand. At least not completely because the nomenclature is usually intricate, since it is usual for each brand to use its own terms to define the characteristics of its products or add certain surnames to try to highlight some feature included in a specific objective.

For this reason we have proposed to make a small guide to understand the meaning of the acronyms that appear in most of the latest lenses on the market. Of course, we have left out those used to distinguish between the different mounts and also the nomenclatures used to differentiate the ranges of each brand, because it is something that would give for another complete article (which we will do if you ask us). So let's go with it.

Common acronyms

Although most use a special nomenclature, there are some acronyms that are common to all brands or are very similar because they refer to the same characteristic.

• F: Actually, the only acronym that is usually common in all brands is F, often identified with the spelling “ƒ”, which refers to the maximum diaphragm opening of the lens, indicating a single number if the focal length is fixed and two values ​​if it is variable focal length.
• AF: This is another acronym common to all lenses that, as you may have guessed, means that the lens is autofocus or Auto Focus. However, for years this technology has been generalized, these acronyms are no longer usually included in its name unless you want to designate some special characteristic referring to the type of focus motor used or similar (which we will see in the next section).
• M or MF: On the other hand, if the lens in question does not have autofocus capability, it may include one of these acronyms to indicate that it is Manual Focus or Manual Focus.
• WR/ AW: From Water Resistant and All Wheather, they are the acronyms that are usually used to refer to the sealing of an optic that makes it resistant to the elements (water and dust) and that is used in different brands.
• PC: From Perspective Control, or "Perspective Control", they are offset optics that allow the parallelism between the plane of focus and the plane of vision to be varied and are mainly used in architecture.
• Macro: This one needs no explanation since its use is common in practically all brands to designate macro lenses, designed to make a very close focus and reproduce elements at real size (ideally 1: 1) in a photograph.

Focus systems

As we said, the different brands often use acronyms to indicate that a lens has a special focus system or motor. For example, the ultrasonic type is very common, an AF system based on ultrasonic waves that allows a fast and fairly silent focus. We also have so-called “step” lenses, which are more recent and are specially designed so that the rotation of the lens (when focusing or zooming) is not heard in video recording.

And there are also internal focus lenses, that is, those in which the focus is produced thanks to an internal displacement of their lenses (the lens does not "grow" in the focus operation). Here are some of the more common acronyms:

• USM: Ultra Sonic Motor used by Canon.
• SWM: From Silent Wave Engine used by Nikon.
• SSM: From Super Sonic Motor used by Sony (Konica and Minolta).
• STM: From Stepping Motor, the "Stepper Motor" used by Canon.
• SWD: From Supersonic Wave Drive used by Olympus.
• XSM: From Extra Silent Motor used by Panasonic.
• HSM: From the Hyper Sonic Engine used by Sigma.
• USD: From Ultrasonic Silent Drive used by Tamron.
• SDM: From Supersonic Dynamic Engine used by Pentax.
• IF / AF-I: From Internal Focus to Auto Focus Internal, used by various brands.

Image stabilization

A section in which there is clearly a problem with the nomenclature of the different brands is that of the image stabilization that some optics include. Although, logically, each one has its own methods to do it, it is still something common and nevertheless receives different names and, consequently, different acronyms:

• IS: From Image Stabilization used by Canon.
• VR: From Vibration Reduction used by Nikon.
• OSS: De Optical Steady Shot usado por Sony y Zeiss.
• OIS/ Mega OIS: De Optical Image Stabilization y Mega Optical Image Stabilization usado por Fujifilm y Panasonic.
• OS: Optical Stabilization used by Sigma.
• VC: From Vibration Compensation used by Tamron.

Correction and improvements

On many occasions we will find acronyms that are used to indicate that a lens in question uses some type of special lens to avoid optical problems such as chromatic aberrations, parasitic reflections, etc. Among these we can frequently find those that designate low dispersion lenses or special coatings:

• ED/ LD/ UD: From Extra-Low Dispersion, Low Dispersion and Ultra-Low Dispersion, used by different brands to designate that the lens uses low dispersion lenses to different degrees (normally different types of lenses are combined).
• SMC: From Super Multi Coated, referring to the multilayer coating of the lenses of some brands.
• ASPH/ ASP/ ASL: From Aspherical, referring to the use of aspherical type lenses (more curved than usual) used to reduce chromatic aberrations in lenses of different brands.
• APO: From Apochromat or “Apochromatic”, it refers to optics that have specially designed lenses for greater correction of chromatic and spherical aberrations.
• XR: From Extra Refractive, used by Tamron to indicate that the lens incorporates low dispersion glass lenses.
• T*: A “T” plus an asterisk on a Sony/Zeiss lens indicates that the lens has special anti- flare and anti-reflection treatment.
• DO: From Diffractive Optical used by Canon to name lenses with diffractive optical elements, used to lighten the size of lenses and control chromatic aberrations.
• FL: Used by Nikon to indicate that the lens includes special fluorite lenses.

Top quality lenses

It is also quite common to find special names that brands use to designate their most exclusive or, at least, higher-end lenses. Let's see the best known:

• L: for Luxury used by Canon for its most exclusive lenses.
• Limited/ “*”: The asterisk or the adjective *Limited* are two of the ways Pentax uses to designate its higher quality lenses.
• G and G Master: Nomenclature to designate the professional and superior ranges of Sony lenses.
• SP: From Super Performance used by Tamron to indicate superior quality lenses.
• EX: De used by Sigma to name their professional quality lenses.