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.
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
- 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.
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
- 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
- XSM: From Extra Silent Motor used by
- HSM: From the Hyper Sonic Engine used
- USD: From Ultrasonic Silent Drive used
- SDM: From Supersonic Dynamic Engine used
- IF / AF-I: From Internal Focus to Auto
Focus Internal, used by various brands.
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
- VR: From Vibration Reduction used by
- 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
- VC: From Vibration Compensation used by
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
- 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
- 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
- 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
- T*: A “T” plus an asterisk on a Sony/Zeiss lens
indicates that the lens has special anti- flare and anti-reflection
- 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
- 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