Dictionary of (digital) photography terms and abbreviations

For people who are new to photography, and even to those who have been around for a while, the ocean of terms and abbreviations used by camera manufacturers can be quite confusing.
They are even worse than the military, whom are notorious for their love of the upper-case short-for.

Of course, every brand has its own favorite denominations, such as VR, OS, IS or IOS, which are all referring to optical image stabilization – either in a lens or in-camera (sensor shift).
Built-in silent focus motors in lenses also go by some unique brand short-for: HSM, USM, XSM, SDM, and SWM, among others, and the stuff you read on lenses or in lens spec sheets, these days, can be a real challenge: AF-S VR Micro 105mm f/2.8G ED Nikkor; G indicates it does not have an aperture ring, while, according to the spec sheet it is IF, features SWM and N, but is not DX – thus, FF or FX. How about that for lettersoup?

It would go too far to create a reference for all the imaginative terms the camera- and lens manufacturers invent and with this being a Nikon related blog, after the break you will find what is a – already very long – list of general photography and Nikon gear terms.
Enjoy!

¿What means AF-S DX IF ED D G fEE SLR APO APS-C HSM CCD?
Last update: 17-10-16. Content & images: © Gerard Prins.
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135-Format/35 mm Format
AE | AE-L/AF-L | ADR | AF | AF-A | AF-C | AF-I | AF-S | AI | AI-S | AoC | AoV/FoV Anti-CA | APO | APS-C | Aspherical
Blur | Bokeh | BSI
CA | CCD/CMOS | CF | Creep | Crop-Factor | CSL
D | D-Type | DC | DG | DoF | DSLR | DX
ED | EX | Exif | EV | EVIL/SLD
F | F- - | FE | fEE | FF/FX | FM | F-Mount | Focal Length | Focal Range
Grad | G-Type
HSM | Hotpixel
IF | Image Measure | IM | IQ
LD | Lens Mount | Live-view | Low-pass Filter
MB-D | MC | MD | Metering (Exposure) | MF | mm | Micro | Multiply Factor | Mount
Nikkor | Noct
Objetive (lens) | One-Touch | OoF | OS
PC | P&S | Prime
RAW | Reflex | RF/Rear Focus | RF/Back Focus | RF/Reproduction Factor | RF/Royalty free | RGB
SD | Sensor | Sharpness | SLR | Sun hood | SWM
TC | TTL
Viewfinder | VR
Zoom
135/35 mm. (Format)	With “135 Format” or also “35 mm Format” we refer to the 24x36 mm film format, used for decades in SLR cameras. Similarly, when referring to a 135 format lens, we refer to a lens with a angle of coverage (see AoC) or projection circle large enough to cover the entire 135 frame, as well as a full frame or “FX” sensor, which is of the same size - the reason for its designation. Today, we make this distinction because there are also so-called DX lenses, which have a AoC large enough to cover an APS-C frame of 16x24 mm, but not to cover a 135 format frame.
AE	Auto Exposure - automatic exposure. In essence there are four modes: Aperture Priority (A), Shutter Priority (S), Program (P, P*, P-Scene) and Manual (M). A and S modes are called semi-automatic, because in A mode the user selects the aperture, while in S mode the shutter speed. In both cases, the camera automatically selects the corresponding shutter speed or aperture to obtain correct exposure. P mode is fully automatic, because the camera selects both the aperture and shutter speed according to the lighting conditions. In virtually all Nikon models there is also a P* mode, which allows the user to modify - within certain limits - the values chosen by the camera. The more economical models also have a number of automatic or “scene” modes, such as portrait, landscape, sports, etc., which define how the program interprets the lighting conditions and selects the appropriate combination of aperture and shutter speed for the scene to be photographed. Note that in P and Scene modes some (or most) of the shooting options may be grayed out and cannot be modified. In M mode exposure metering is automatic, but users must select both the aperture and shutter speed according to the photometric information available in the display and/or control panel and decide on their own which is the most suitable combination for the scene at hand. See also: exposure metering, methods.
AE-L / AF-L	Auto Exposure Lock, Auto Focus Lock. Button that locks exposure and auto focus at the measured values at the time of pressing. On the large mayority of Nikons, the button functions can be set in the custom menu (CSM) to one of the following: AE/AF lock (default), AE lock only, AF lock only, AE lock hold, AF-ON. The latter option is only available if the camera does not have a dedicated AF-on button as is the case of the D200-D500 and D1-D5 series.
ADR	Aperture Direct Read-out. A additional series of small numbers, engraved on the aperture ring of all AI, AI-S and AF(S) type D lenses (photo above), which allows reading the selected diaphragm directly from the view finder of non-electronic cameras, through the ADR window located at the front bottom part of the prism (see photo here).
AF	Auto Focus - automatic focusing (Leitz/Leica, 1960-1973). There are different auto focus modes, which can be either passive or dynamic. Available modes depend of the camera model: AF-A, AF-F, AF-C, AF-S and M. Some of Nikon’s in-camera auto-focus systems are: Multi-CAM 1300 (12-1999) with 5 sensors (D1 Series), Multi-CAM 2000 (12-2003), with 11 sensors and 4 dynamic area modes (D2 series, D200, D90), Multi-CAM 3500 (08-2007) with 52 sensors and 6 dynamic area modes (D3 series, D700 and D300[s]). For the latest on AF, you may want to read this article
AF-A	Automatic AF. The camera decides between AF-S and AF-C, depending on the shooting situation. Available on more economical cameras.
AF-C	Continous servo AF. In AF-C the camera constantly adjusts focus once acquired, whenever the subject or the camera change position or distance, as long as the user keep the shutter release-, AE-L/AF-L or AF-ON button pressed.
AF-I	Internal Auto Focusing (Nikon - 1976). Moves optical elements inside the lens, resulting in faster auto focus, because the focusing motor needs to move fewer optical elements over shorter distances. An additional advantage is that the lens’ front end does not rotate, facilitating the use of orientation sensitive filters, such as polarizers. Although all Nikon DSLR’s are compatible with AF-I, the system was only used in very fast lenses (f/2.8 - f/4) with focal lengths from 300 to 600 mm., which – even today – are worth thousands of dollars. Nikon abandoned AF-I in 1995 for AF-S.
AF-S	Single servo AF. In AF-S, the camera acquires focus once, and does not adjust to changes in position, distance of the subject or camera, as long as the user keep the shutter release-, AE-L/AF-L or AF-ON button pressed.
	Silent Auto Focusing. Nikon Designation for lenses with a built-in “Silent Wave Motor” (SWM), which enables fast and quiet auto-focus. AF-S is considerably faster and quieter than the older AF-D system, where a focusing motor in the camera is responsible for driving focus adjustments. The difference between expensive AF-S lenses, like the 17-35 mm f/2.8D, and the (much) cheaper ones – like the 18-55 f/3.5-5.6G – is that the latter have a more simple motor and are of variable aperture, while the expensive ones are constant aperture (does not change with zoom). In addition, the expensive ones have Internal Focus (IF) and are FX (full-frame), while the cheap(er) ones are mostly DX and do not feature IF; their front end extends on zoom and it rotates when focusing. If the cheaper lenses are marked as ED, they generally have only one element of low dispersion glass, while the more expensive models may have 3 or more.
AI	Auto Indexing (Nikon 1977). System that allows “coupling” between the diaphragm of a lens and the camera. AI and AI-S compatible Nikkor lenses have a rim on their mount, which mates with the meter coupling lever on the camera, thus allowing the indexing of the diaphragm (see image). This way, the camera can index the maximum aperture of the lens, which in turn enables TTL metering at the maximum lens opening. All MF and AF D-type Nikkor lenses from this date on have a second set of small ADR numbers engraved on the aperture ring, which allows confirmation of the selected aperture from the viewfinder of Nikon cameras without an electronic interface, through the ADR window at the lower front part of the roof prism (foto above). AI and AI-S lenses can be mounted used in MF mode with most of the post 1977 film cameras, however, on the entry-level models the exposure meter does not work (D40-D100, D3000- and D5000 series). The camera’s mode dial must be set to M. In all other modes (A, S, P), the camera shows a flashing F-- symbol on its screen(s), viewfinder and will NOT fire. All models of the Dx series (D1-D5), the D200, D300(s), D500, D600/610, D700, D7000 series and D800/810 AE  meter in A or M mode, with center-weighted metering. From the D2/D200 models on, the user can manually enter lens data (max. aperture, focal length) into the camera’s lens database, thus enabling color matrix metering and the inclusion of shooting related meta-data in Exif. Note: the maximum aperture of the lens may not exceed f/5.6 (f/1.8, f/2.8, f/4, etc.). AI-P (“chipped” MF) lenses can be used on all D models with exposure metering; available AE mode(s) depend on the camera model. For more information, consult your owner's manual. Although we have come to denominate Nikkor MF lenses as AI or AI-S, all Nikkor and third-party AF lenses with and without aperture ring (D and G type) also comply with the AI-S specification. IMPORTANT NOTE: Pre-AI (Non-AI, NAI, F-type) lenses should NOT, under any circumstance, be mounted on post AI bodies (1977), as they may cause serious damage - like destroying the mirror. However, in most cases the damage make be less noticeable, because pre-AI lenses typically deform the metering coupling lever. Although on some cameras it can be unlocked and moved out of the way, on most it cannot. See this article for more information.
AI 50 mm. f/1.4 Nikkor and AI-S 35-105 mm. f/3.5-4.5 Macro Nikkor. (Note: on the latter the pre-AI prong has been removed)
AI-S	Auto Indexing Shutter, evolution of AI (Nikon, 1981). Lets the camera align the diaphragm via a small pin, which allows for more precise metering: TLL measures the incident light AFTER closing the diaphragm and before opening the shutter. The most visible difference is that these lenses have their minimum aperture marked in orange, while they also have a small semi-circular notch in the F-Mount (AI-S identification gouge), which allows the camera to identify them as AI-S. The major internal difference is that they have a linear action diaphragm (coupled through the automatic diaphragm pin), allowing higher shutter speeds. Although we have come to denominate Nikkor MF lenses as AI or AI-S, all Nikkor and third-party AF lenses with and without aperture ring (D- and G type) also comply with the AI-S specification.
AoC	Area of Coverage. Area covered by the projection of a lens on the focal plane (film or sensor) and which – therefore – must be superior in size. Where a lens projects a so-called “image circle” or “projection circle” while the focal plane is square or rectangular, optical flaws, such as unsharpness or distortion, are most evident at the corners of an image. Similarly, when the area of the focal plane of the camera exceeds the Area of Coverage or the Angle of View (AoV) of a lens, we can observe an optical defect called vignetting, which is a circular darkening – light fall-off – towards the corners of a square image, and the horizontal edges of a rectangular image. Vignetting is mostly associated with wide-angle lenses at their maximum aperture, and can generally be solved by stopping down (the diaphragm) and/or in post-production, except in the case of DX lenses mounted on film cameras. (See also 135/35 mm format, MF Format) Nikon FX (full-frame) cameras can be configured to automatically crop the image when a DX Lens is mounted.
AoV/FoV	Angle of View, also called Field of View. Refers to the part of a scene that a lens is capable of capturing, and should not be confused with “angle of coverage” (AoC) which describes a lenses’ projection area on the focal plane. AoV is measured in degrees, on the horizontal, vertical and diagonal axis. The horizontal viewing angles for some typical 135 format lenses are: 24 mm: 73.7 ºH, 28 mm: 65.5 ºH, 35 mm: 54.4 ºH, 50 mm: 39.6 ºH, 135 mm: 15.2 ºH, 200 mm: 10 3 ºH, 500 mm: 4.12 ºH. Tamron has a handy Flash tool for comparison of the AoV of the various focus lengths here (ranges from 10-500 mm.). It also allows comparison between 135 format (film, FX) and DX (APS-C).
Anti-CA	In-camera Chromatic Aberration (CA) suppression system. Used on certain Nikon models (D300, D700, among others) that use the power of their EXPEED processing engine to analyze a captured image and remove CA (if present) before writing the information to the memory card. This system only works with JPG files; to eliminate CA in NEF files (Nikon RAW), the Nikon Capture program must be used which, although generally effective, is optional and expensive.
APO	Sigma designation for Aspherical lenses. (See Aspherical)
APS-C	The type of sensor used in Nikon DX format cameras (other brands use different Designations). It measures 24x16 mm., which equals 2/3 of a 35 mm film frame. More information This is currently the most widely used sensor in DSLR cameras and cause for the so-called crop-factor, also – mistakenly – called multiply factor (See crop factor).
Aspherical	Usually used in reference to a lens that has one or more a-spherical elements in its configuration. An aspherical lens has a different frontal and rear curvature, which helps to eliminate and/or reduce optical defects and aberrations, particularly Chromatic Aberration (CA). More information >
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Blur	Smearing or lack of sharpness due to camera shake (camera blur) or when shooting moving subjects at low shutter speeds (motion blur). In the case of lenses, we speak of "Lens blur" when a given lens is incapable of achieving the required sharpness – mostly in the corners of an image – or due to other optical defects such as front-, back focus or optical aberration.
Bokeh	The word comes from the Japanese Boke, which means blurry. It refers to the way a lens generates light points in out of focus areas, when used at or near its maximum aperture, which creates a shallow depth of field (DoF). Bokeh is not the same as “Blur”, because blur is the result of a defect, either optical or of camera management (see Blur) Bokeh is largely a matter of taste, however, most photographers agree that Reflex lenses have the least pleasing bokeh, because they yield out of focus (OoF) light sources as donut-shaped rings. Good photographers take advantage of the bokeh typical of certain focal lengths, to add to the composition, dynamics and atmosphere of a shot.
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CA. Effect exagerated in Photoshop.
CA	Chromatic aberration. Occurs when the lightrays of different wave-lengths do not coincide at the focal plane (where a lens is sharp). They may either focus at a different focal points – ahead or behind the focal plane – or be slightly displaced in relation to one another. This leads to the red, green and blue (primary CA) yellow, blue or purple (secondary CA) fringes that sometimes mark high-contrast edges in an image. Although this is generally considered to be an optical defect in lenses, it may also have to do with the lens-sensor combination (see sensor, anti-CA). In the particular case of purple fringing, this may also be caused by so-called “sensor blooming”: the overload of the pixels or photo-sites on the sensor, generally due to overexposure. This phenomenon is most common in P&S type cameras because of the inferior size and quality of their sensors, however, this does not mean it is absent in DSLR's.
CCD/CMOS	CCD: Charge Coupled Device. Light-sensitive RGB semi-conductor chip, found in video cameras, scanners and digital cameras (amongst others) able to translate light into an electrical charge and convert that into an analogue electronic signal. More information > CMOS: Complementary Metal Oxide Semiconductor. Idem, but converts the electrical charge into a digital electronic signal. More information: Nikon CMOS FX > The difference is that in a CCD sensor the signal of all pixels is output through a few channels and as an analog signal, where a CMOS is multi-channel because every pixel converts its own signal. A CMOS sensor generally incorporates per pixel signal amplifiers, correction and noise reduction circuitry and AD converters, and therefore outputs a digital signal. Some experts claim the CCD may “be running out of steam”, because it requires a dedicated, relatively expensive manufacturing process, where CMOS can now be produced in “fabs” that turn out all kinds of standard semi-conductor chips. Both sensors are used in digital cameras, from FX and DX DSLR’s, to the most modest P&S. Nikon currently employs CMOS in its professional and semi professional line-up from the D3X to the D5000, and CCD in the D3000, D80, D70, D60, D40 and the large majority of its Coolpix cameras.
CF	1 – Compact Flash (CF-I, CF-II). “Solid State” type Memory Card, mainly used in professional and semi-professional cameras. Other commonly used types are: SD, Memorystick (Sony), MMC y xD. More information >
	2 - Close Focus. Refers to the ability of a lens to focus, even at a very short distance of a subject. This is usually only possible with specialized Macro lenses, bellows, extension tubes or an inversion ring, which allows lenses to be mounted reversed.
Creep (lens)	With lens-creep we refer to the tendency of a zoom lens to slide under its own weight toward the forward end of its zoom trajectory - usually its maximum focal length. Creep can be particularly uncomfortable when shooting vertically, when the only way to avoid creep is to keep one’s hand on the zoom ring. Some lenses who suffer from this problem, have an “anti-creep” button, which locks the zoom at its shortest extension, thus preventing it from sliding down - at least during transport.
Comparison between the viewfinder of a Nikon film and DX camera clearly shows how much is lost to the crop factor.
Crop-Factor	The 30% trim that applies to cameras with an APS-C sensor (DX), which crops the projection circle of 135 format lenses (35 mm., FX or full frame) on the focal plane to two thirds of its usable, due to the smaller size of the sensor chip in comparison with film (16x24 mm). See also: angle of coverage (AoC). An advantage of the crop factor is that it trims down to the center of the projection circle of full-frame lenses, where they are usually the sharpest, and suffer less from optical defects and aberrations, vignetting, distortion and blur. This is not the case with DX lenses, which have a smaller AoC, and suffer on an APS-C camera from the same defects as 135 format lenses on a digital full-frame or film camera. The crop factor is also called mistakenly called “multiply factor” which is not correct because the lens does not multiply its focal length. Rather, its angle of view (AoV, FoV), is “trimmed down” by the sensor, “enlarging” it by a factor of 1,5 for Nikon and 1.6 for Canon. The latter also produces some cameras with an APS-H sensor with a crop factor of 1.3. This implies that on a Nikon DX camera, a 135 format 24-mm. lens has an AoV equivalent to 36 mm. and a 300 mm. lens that of a 450 mm.. For Canon, these numbers are 38.4 and 480 mm. (APS-C) and 31.2 and 390 mm. (APS-H), respectively. The crop factor has created a new market segment of so-called “extreme” wide-angles (10 to 18 mm.), because what was once considered a wide-angle or extreme wide-angle lens, multiplied by 1,5 becomes a standard or moderate wide angle lens: 21 mm. (AoV: 81.2 ºH) = 31.5 mm. (AoV: 59.3 ºH); 24 mm (AoV: 73.4 ºH). = 36 mm. (AoV: 53.8 ºH); 35 mm. (AoV: 54.3 ºH) = 52.5 mm (AoV: 37.5 ºH).
CSL	Creative Ligthing System. Nikon denominación for their last generation of iTTL flash equipment (SB 600 AF, SB 900 AF, etc.).
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D	Designation of Nikon Digital SLR’s ever since the launch of the Nikon D1 (Professional, 1999) and D100 (Semi-professional - 2002).
D-Type lens (AF-S 17-35 mm. f/2.8D IF ED)
D-Type	Distance, D-Type. Designation of Nikon AF or AF-S lenses with an aperture ring, unlike G-Type lenses, which have none. The D or G marks follow that of the f/max. engraved on the lens (as 1:2.8D, 1:3.5-5.6G) and indicate that they are compatible with 3D Matrix and 3D Color Matrix I and II exposure metering (on compatible cameras). Both can convey distance information, which the metering calculations use to optimize exposure. All D and G lenses are also compatible with the AI-S specification, as can be seen on the aperture ring of D lenses, which include the ADR scale, in addition to having their minimum aperture marked in orange. On cameras with control dial(s), the aperture ring of a D-Type lens must be locked at its minimum aperture (typically f/16 or f/22) since aperture is handled directly from the camera body with the Main or Secundary command dial (according to configuration). When a lens is NOT locked at its minimum aperture, the camera shows an intermittent fEE error on its display(s), viewfinder and will refuse to fire.
DC	Confusing Sigma Designation of lenses designed for DX (APS-C) cameras. Most manufacturers talk about DX, at least in the case of Nikon mount lenses.
DG	Confusing Sigma Designation of lenses designed for 135 format (35 mm.) and digital FX (FF, Full-Frame) cameras. Most manufacturers talk about FX or FF, at least in the case of Nikon mount lenses.
DoF	Depth of Field is apparently one of the hardest concepts to understand for starting photographers. With depth of field we refer to the point or the distance between two points where a subject is in focus (sharp), while everything outside this point or area is less sharp or blurred. We talk about shallow or large depth of field, which is directly related to the selected aperture: large aperture (f/2.8) - shallow DoF; small aperture (f/22) - large DoF. For example: the AI 50 mm. f/1.4 Nikkor has a depth of field of a few mm. at f/1.4, at f/4 a close-focus DoF from 80 to 85 cm., and long-focus DoF from 5 to 10 meters. Meanwhile, at f/16 (minimum aperture) close-focus DoF is 70-90 cm. and long-focus DoF goes from 2 to 10 meters and 3 meters to infinity. Good photographers take advantage of DoF with selective focus and the blur effects and “bokeh” typical of certain focal lengths, to add to the composition, dynamics and atmosphere of an image. Tamron has a practical DoF comparison tool here.
DSLR	Digital Single Lens Reflex. A SLR camera with a sensor that records on a memory card instead of film.
DX	Coding system for 135 format film cartridges (35 mm), which allows compatible cameras to determine film speed (ASA 100, 200, 400, etc.) and number of takes (12, 24, 36).
	Designation for Nikon digital SLR cameras with an APS-C sensor of 24x16 mm.. In the case of lenses, these have a smaller projection circle (see AoC) than those designed for 135 format film cameras (35 mm.) or full frame DSLR's (FF/FX), which allows for more compact, light and economical designs. However, these lenses cannot be used on film cameras. Nikon FX cameras (for example, D3X, D700) can be set to automatically crop down when a DX lens is mounted, however, the resulting images are only half the camera’s native resolution. As a result, DX images from the D3X (24.5 Mp.) are 12.1 Mp. and from the D700 (12.4 Mp.) only 5.1 Mp..
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ED	Extra low Dispersion glass (Nikon 1975), has the grace to eliminate or reduce secondary chromatic aberration (yellow-purple), especially in long (300 mm. and longer) and fast (large aperture: f/2.8, f/4) lenses..
EX	Designation Sigma’s line of professional lenses, such as the 100-300mm f/4 EX APO HSM.
Exif	Exchangable image file format. System which enables digital cameras and photo editing programs to embed meta-data tags (labels) in the image header of JPG, TIFF and RAW files, such as – for example – shooting date and time, exposure, aperture, lens model and max. aperture, copyright, GPS data, flash values, etc., etc. More information>
EV	Exposure Value. Also popularly called exposure stop. The result of the increase or decrease of the amount of light entering the camera by opening or closing (stopping down) the lens diaphragm one step or stop: from f/2.8 to f/4 to f/5.6, etc. Each of these steps is equivalent of 1 EV, and by “stopping down” the exposure time doubles, while the inverse is true for opening the diaphragm one stop. For example f/2.8 @ 1/500s is equivalent to f/4 @ 1/250s and f/5.6 @ 1/125s.
EVIL/SLD	Electronic Viewfinder, Interchangeable Lens, also called SLD - Single Lens Direct View. New interchangeable lens camera cathegory, akin SLR, but without the mirrorbox and pentaprism. Instead, these cameras feature an electronic on-screen viewfinder for direct visualization, akin standard P&S cameras. They can, therefore, be much more compact, without losing the advantages of interchangeable lenses.
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F	Designation for Nikon film cameras of the Japanese Nippon Kogaku company, since the first Nikon F with F-Mount (1959), until the last models still in production today, the F6 and FM10.
F- -	Blinking symbol on the display(s) and viewfinder of a Nikon DSLR when you mount a manual focus (AI, AI-S) lens which the camera is incapable of indexing (read its maximum aperture), and/or coupling to its exposure meter. In most cases, you can still take pictures, but with certain limitations. For more information, check out this article.
Nikon FE with AI 50 mm. f/1.4 and MD-12 motor drive
FE	Nikon FE (1978), electro-mechanical SLR film camera with semi-automatic TTL aperture priority exposure metering, or – alternatively – manual metering. Specifically designed for use with AI (1977) and AI-S (1981) manual focus lenses. The camera is basically mechanical, but both the exposure meter – with overlapping needle system – and the focal plane shutter are electronic.
fEE	This error code blinks on the screen(s) and in the viewfinder of a Nikon body with control dial(s) when the aperture ring of a D-Type lens has not been locked at its minimum aperture (largest f-number, generally f/16, f/22 or f/32). For more information see the “Error messages” section in your camera manual.
FF/FX	Full Frame. Designation for a digital SLR camera with a sensor the size of a 135-format film frame (24x36 mm.). Nikon full-frame cameras (D3S, D3X, D3, D700) are labeled FX. Because the sensor is the same size as a 135-format film frame, FF/FX cameras do not suffer from the APS-C crop factor. Thus, on FX cameras all lenses maintain the same angle of view (AoV/FoV) as on 135-format film cameras because the sensor does not crop their projection circle (AoC).
FM	Nikon FM (1977), mechanical SLR film camera with a manual TTL exposure system. Specifically designed for use with AI (1977) and AI-S (1981) manual focus lenses. Unlike the Nikon FE, the FM's focal plane shutter is mechanical, and the camera uses batteries only to power the LED’s of its exposure meter.
F-Mount	The Nikon-F mount, introduced in 1959, has survived basically unchanged for 50 years, unlike the Canon mount, which has seen five – not always backward compatible – changes in the same period (R, FL, FD, new FD y EOS). Today, you can mount virtually all Nikkor AI (1977) and AI-S (1981) manual focus lenses on virtually any Nikon body. More about the Nikon F-Mount on Wikipedia > On all professional Nikon DSLR’s since the D1, and semi-professional DSLR’s since the D200, these lenses can be mounted and used with either aperture priority or manual, center weighted, auto exposure (AE) metering. On the D40-D100 models, AI and AI-S lenses can be mounted, but the exposure meter does not work. For more information, read this article> Important note: do NOT mount F-Type (non-AI, pre-AI) lenses previous to 1977 on a body of later date. These lenses may damage your camera beyond repair!.
Focal Length (mm.)	The focal length of a lens is measured in millimeters from the center of its front element to the point where its projection converges on the focal plane, in other words: where it is focused or sharp. For the 135-format a lens with a focal length in the order of 50 mm. is considered “standard”, since it reproduces the approximate angle of view (AoV/FoV) of the human eye and matches its “zoom” ability. Other focal lengths are defined relative to this length as: • “fisheye” (circular or diagonal): 6, 8, 10, 12, 14, 16 mm. • “super wide-angle” or “wide-angle”: 10, 12, 14, 16, 18, 20, 21, 24, 28 and 35 mm. Fisheye and wide-angle lenses have a larger AoV than the human eye, but subjects appear to be (much) farther away. • “standard”: 45, 50, 55, 60 mm. • “short tele” or “portrait”: 70, 85, 105, 135 mm. • “tele”: 200, 300 mm. • “super tele”: 400, 500, 600 mm and more. The longer a lens, the greater its ability to bring a subject “closer” (enlarge it in the view finder), at the cost of an increasingly smaller angle of view: a 24 mm. lens has an AoV of 73.7º, while a 500 mm. lens one of only 4.12º. Fixed focal length lenses (50, 135, 400 mm., etc.) are called “Prime” while lenses of variable focal length (18-55 mm, 70-210 mm., etc.) are designated “Zoom”. The latter have the ability to change their focal length and, thus, the perceived size of the subject (Image Measure) in the viewfinder or on the focal plane (film, sensor). The distance between a zoom lenses' shortest and longest focal length is called “Focal Range”. Tamron has a handy Flash tool for the comparison of different focal lengths here (on both DX and film [FX], range: 11-500 mm.).
Focal Range	The distance or difference between the shortest and longest focal length of a zoom lens.
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Different filter-types. On the right, graduated orange, neutral density (ND), purple and “sunset”.
Grad	Gradual color-to-transparent filter, also called “Cromo”. They are used to change the tone or atmosphere of a picture, and are mostly - but not exclusively - applied on the sky. Grey grad filters are called “Neutral Density” (ND), come in several densities and are generally used to modify the luminosity of the sky in shots with dark foregrounds - like sunsets for example - where they allow exposing for the shadow areas, while preventing over exposing (blowing) the highlights, or, in other words: maintain detail and color in the sky and clouds.
G-Type	Designation of AF and AF-S Nikon and third-party F-Mount lenses without aperture ring. The aperture of these lenses is controlled directly from the camera, through the main or secondary command dial (according to camera model and configuration). Therefore, these lenses cannot be used on cameras without at least one control dial. All other characteristics are identical to those of D-type lenses, including the ability to provide distance information, which enables 3D Matrix and 3D Color Matrix I and II exposure metering.
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HSM	Hyper Silent Motor. Designation for the silent AF motor built into Sigma's flagship lenses. This system is mostly used in internal focus (IF) lenses and similar to the Silent Wave Motor (SWM) built into Nikon's top AF-S lenses.
Hotpixel	Hot pixels are easily recognizable because they always come in a cross-shape, their center pixel is always brighter than the pixels in the four “arms”, and they come - without exception - in a primary RGB color: red, green or blue. They are the result of: 1 - A failed pixel in the sensor, in which case it is called a “dead pixel”. If a camera still has its warranty, I recommended trying to swap it, or request the pixel(s) to be “programmed out” (not always possible). Otherwise, it is the inevitable result of aging and can be easily retouched. 2 – Over demanding the sensor, generally with a long exposures or high ISO’s. For example: the Nikon D1x was notorious for generating hotpixels at exposures of more than 2-3 seconds and ISO’s over 400. Modern cameras hardly suffer from this problem anymore, even though my D200 may sometimes generate a few hotpixels at very long (30 seconds and more) exposures.
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IF	Internal Focus. Lenses with internal focusing have the grace to focus faster, because they internally move fewer optical elements over shorter distances, in modern AF-S lenses with the help of a dedicated, built-in focusing motor. An additional benefit of IF is that the lens’ frontal element or front end does not extend on zoom nor rotate, which allows for the use of petal shaped lens hoods and orientation critical filters, such as polarizers and grads (See also AF-I, AF-S).
Image Measure	Proportion between the size of a subject and the size of its projection on the focal plane (sensor, film). At a fixed camera-subject distance, the Image Measure of a 50 mm. lens is approximately half that of a 100 mm. lens (50%) and slightly more than twice that of a 24 mm. lens (204%).
IR	Infrared. Photography that captures the infrared light spectrum (between 700 and 1200 Nm.), which is invisible to the human eye. IR images can be captured using filters and/or specialty films, while digital sensors are also suitable for IR photography. Its applications range from scientific - astronomy and medicine, for example - to artistic photography. More information >
	Infrared. Light rays, invisible to the human eye, used in cable-less remote control systems for cameras, such as ML-L3 remote control for the Nikon D40 to D90 cameras or the ML-3 Modulite for Nikon (semi) professional cameras. Modern flash systems also make use of infrared for the synchronized remote “triggering” of one or more off-camera flashes.
IQ	Image Quality. This term is generally used when comparing cameras.
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LD	Low Dispersion. Glass used in photographic lenses (See ED).
Lens-Mount	A system that allows securely mounting lenses on an interchangeable lens reflex camera or (D)SLR. There are two types: threaded and bayonet. The first is a system called M42 or Praktica-mount. M42 lenses have a threaded extension, which screw fits into the camera mount. It takes several turns to assure that the lens is properly seated. In the case of a bayonet, the lens has 3 protruding edges (bayonets) which fit the slots of the camera mount. A twist in the order of 120° suffices to correctly mount the lens on the camera. From the 1960's on, the bayonet quickly began to replace the M42 thread and today, the system is dominant. This is due to its quick mounting, as well as its ease and accuracy in providing proper alignment and connection for the complex electronic systems in modern cameras and lenses, such as distance measurement, auto focus, image stabilization, exposure metering, etc.. Brands which use a bayonet mount are Nikon (F mount), Canon (R, FL, FD, new FD and EOS mounts), Olympus (OM mount) and Pentax (K mount), amongst others. Unfortunately, bayonet mounts are proprietary, which makes it practically impossible to use the lenses of one brand on the cameras of another. More information >
Live-View	Real time display, much like what you see on the screen of any compact digital camera. The difference is that a (D)SLR is designed to display the image in the viewfinder through the lens and via a mirror plus a (penta) prism, which means that it needs to raise and lock the main mirror, or be equipped with a “see-through mirror” or additional sensor to be able to display the subject on the camera’s monitor.
Low-pass filter	Optical anti-aliasing filter which is an integral part of a photo-sensitive sensor (CCD/CMOS). Applies an indistinguishable blur, which avoids pixelation (staircase effect) on contrasting edges and moiré (cross-line effect) in fine details and repetitive patterns. The sensor cleaning systems built into some digital cameras do not actually “clean” the sensor but the low-pass filter of adhering dust and small particles.
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Macro	Extreme close-up photography, where the distance between the lens and the subject is in the range of a few millimeters to a few dozen centimeters. This can be achieved with dedicated macro- or zoom lenses, bellows, extension tube(s) or the inverted mounting of a lens with an inversion ring. Generally a shot is only considered a “true macro” when it has a reproduction factor or image measure of 100%, meaning that the image on the focal plane (film, sensor) is the same size as the live subject.
MB-D200. Battery pack for the D200
MB-D	Nikon multi-battery pack. Designation for the optional multi option battery packs (proprietary, alkaline, rechargeable) also called “vertical shooting grip” such as the MB-D90 (D90), MB-D200 (D200), MB-D10 (D300, D700), etc.. Depending on the model, it includes an AF-ON button, a shutter release button with button lock and the main and sub command dials.
MF and AF lenses of different focal lengths. The colors come from their coating.
MC	Multi-coated. Designation of optical elements with multiple layers of some type of coating material (such as magnesium fluoride), which helps to improve light transfer, to reduce internal reflections and to combat optical defects in a lens. Today, the vast majority of lenses is MC or at least SC (single-coated). Coated lenses can be easily recognized when observing the light refraction on their surface, because they show a wide variety of colors, the hue of which depends of the coating material used.
MD	Nikon Motor Drive o winder. Optional, “bolt-on” film transport motor or “motor drive” (MD-11, MD-12) for Nikon semi-professional film cameras like the FE and FM.
Metering (Exposure)	Exposure metering methods. Essentially they are three: “Matrix”, which calculates exposure taking the luminosity of the entire frame into account. “Center-weighted”, which uses the information of entire frame, but places emphasis on a central area of 8 mm. (Marked on the screen, customizable on certain Nikon DSLR’s). “Spot”, which calculates the exposure measuring a circle of 3 mm. at the focus point (Customizable on certain models).
MF	Manual Focus. There are four types of MF Nikkor lenses: AI (1977), AI-E (1979) AI-S (1981) and AI-P (1988). The latter come with a built-in chip, allowing electronic coupling with most modern Nikon bodies, which makes it possible to use them with different (semi) automatic exposure (AE) programs - usually Aperture priority and Manual but sometimes also Shutter priority and Program (depending on camera and lens model).
	Medium format. Named so because it lies in between the 135-format and the large image sizes of the so-called technical or flat-film cameras: 4x5" (10x12,5 cm.), 8x10" (20x25 cm.) and larger. The most common MF film and sensor sizes are: 6x4,5 cm. (Format 645), 6x6 cm. (Format 66) and 6x7 cm. (Format 67). Some manufactures of MF cameras and backs are: Phase One, Hasselblad and Mamiya.
mm	Millimeter. In a photography and/or optics context primarily used to indicate the focal length of lenses.
Micro	Nikon designation for dedicated Macro lenses. Currently available models come in the focal lengths of 60, 85, 105 and 200 mm. (AF), 55 and 105 mm. (MF), all capable of a reproduction factor or image measure of 100% (1:1). Nikon also offers a MF Micro 85 mm. lens with Perspective Control (PC).
Multiply factor	See Crop factor.
Mount	See lens-mount, F-Mount.
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Nikkor	Brand name of Nikon’s premium lens line for over 75 years. The first lens of this name was the 1933 “Aero-NIKKOR”, designed for aerial photography.
Noct	Very high brightness lenses, such as the f/1:1 Leica Noctilux and the f/1:1.2 58 mm. NOCT-Nikkor, specifically optimized for nocturnal photography. They are designed to avoid glare on point light sources, and corrected for color shifts related to artificial light sources such as fluorescents and sodium-vapor public lighting (green, orange).
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14-24 mm. f/2.8G Nikkor: 14 elements (lenses) in 11 groups, 3 aspherical, 2 ED.
Objective (optics)	Correct term for what in photography is popularly called a “lens”. The difference is that – in the strict sense – a lens is a single optical element (as in eye glasses), while a photographic objective is a combination of optical elements (lenses) and groups of optical elements with different characteristics. When the technical specifications of an objective indicate it is constructed of X elements in X groups, it means that it contains X lenses which are either stand-alone or combined in groups of 2, 3 or even more, often closely packed together. More information: Lenses, Objectives.
One-Touch	Reference used to identify zoom lenses that combine focus and zoom in one single ring, unlike the “standard” models with two dedicated rings, called dual-ring.
OoF	Out of Focus.
OS	Optical stabilization. Sigma designation referring to the image stabilization system built into a lens (See VR).
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PC	Perspective Correction (Nikon 1965). Highly specialized lens, which imitates the bellows-movements of view-cameras, allowing to correct perspective as well as precise control over focus (selective focus), which is particularly useful in architectural photography. A PC lens allows front element movements – up and down (tilt) left and right (shift), angle and rotate – in relation to the optical axis and the focal plane, resulting in very precise focus control and the possibility to correct the so-called “Scheimpflug” effect, which is the exaggerated perspective or inward inclination of converging lines, particularly noticeable in wide-angle lenses.
P&S	Point & Shoot. Automatic compact camera with a built-in fixed or zoom lens (not interchangeable). Generally speaking, their image quality is inferior to that of DSLR cameras due to the smaller size of their sensors. These are mostly 1/17" (7,6 x5,2 mm - 48 mm2) or 1/2.5" (5.76x4.29 mm - 25 mm2) compared to 24x16 mm (370 mm2) for a APS-C DSLR.
Prime	Lenses of a fixed focal length (not zoom). The most common 135-format primes are: 10.5, 14, 16mm (fish-eye or extreme wide-angle), 20, 21, 24, 28, 35mm (wide-angle), 45, 50, 55, 58mm (Standard), 85, 105, 135mm (short tele), 150, 180, 200, 300mm (long tele), 400, 500, 600 and 800mm (super or ultra tele). More on Nikkor lenses>.
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RAW	Native format that DSLR cameras (and also some more expensive P&S) use to record an image. Unlike JPG, the camera does not process the information output by the sensor, but writes it as is (raw=unprocessed) to the memory card. The format has several important advantages: loss-less compression, greater color depth (12 or 14 bits per RGB channel compared to only 8 bits per channel for JPG) non-destructive corrections in post production of - among others: exposure (+/- 2 EV typically), highlight recovery and clarifications of shadows, correction of white balance, color profile, sharpness, contrast, color balance, saturation, image size, etc. RAW processing programs are capable of demosaicing the RAW sensor image information and extrapolating it into 48-bits (16 bits x 3 channels RGB) PSD, TIF or 24 bits (8 bits x 3 channels RGB) PSD, TIF and JPG. The RAW format is considered to be a “digital negative” and from a quality point of view, JPG is a mere printout in comparison. Nikon’s proprietary RAW file format is called NEF (Nikon Electronic File). You might want to read this article for more information.
Reflex (camara)	The Single Lens Reflex or SLR camera uses Through The Lens (TTL) viewing, metering, focusing and exposing, while the Twin Lens Reflex or TLR camera (such as the Rolleiflex, for example) uses one lens for viewing, metering, focusing and a separate lens for exposing.
Reflex (lens)	Reflex or “mirror” lenses, such as the 500 mm. f/8 Reflex-Nikkor (discontinued) are quite exotic in their optical design, because they achieve very long telephoto lenses in a compact housing. This is accomplished through the Maksutov Cassegrain principle, which uses two mirrors to multiply the lens’ physical focal length through internal reflection. The great advantage of this system is that it “compresses” extreme focal lengths (between 500 and 1200 mm.) into a lightweight, compact, barrel-type package. Disadvantages are that reflex lenses are MF and have a fixed aperture – generally f/8 or f/11 – complicating focusing in low light to the point of the imposible due to the dim image in the viewfinder. Furthermore, their bokeh is considered ugly by the vast majority of photographers, because they render out-of-focus light points as donut-type rings.
RF/Rear Focus	Rear Focus 1. Internal Focusing (see IF) system that moves optical elements at the back-end of a lens, unlike standard IF, which generally moves optical elements at the center or front-end of a lens (illustration: Canon).
	Rear Focus 2, also called "back focus". Optical defect that causes a lens to project its focal point (where it is sharp) behind the focal plane. There is also a defect known as "front focus" where a lens projects its focal point ahead of the focal plane. Both defects are cause of unsharpness or “focus blur”, which may be corrected by adjusting the position of one or more optical elements in the lens. There is a related phenomenon, called optical aberration, which – for different reasons – also causes blurring. This phenomenon occurs because the light waves that pass through different points of an optical element (or lens) have different focal points, in other words: do not coincide. This flaw has to do with imperfections in the lens, and cannot be corrected. Also see: Chromatic Aberration.
Animated illustration. Click to open, then roll the cursor over the texts at the upper right to observe the different phenomena.
RF/Reproduction Factor, Ratio	Reproduction Factor, also Reproduction Ratio. The reproduction factor is measured in percentages and expressed as proportions. 1:1 is 100%, 1:2 is 50%, 2:1 is 200%, etc.. RF refers to the proportion in which a subject is reproduced on the negative or the sensor, while the size in which the subject appears in the view finder or the image is called Image Measure. An Reproduction factor of 1:1 is considered the most genuine, because it presumably does not introduce any optical distortions in the photographic reproduction of a given subject. Nikkor Micro lenses are 1:1, most other lenses usually do not go beyond 1:2, except when mounted inverted (with an adapter ring), on a bellows or extension tubes.
RF/Royalty free	Royalty free images can be used at will once bought, unlike normal stock images where every use must be clearly defined and paid for separately.
RGB	Red-Green-Blue. Additive color composition system, comprising the primary colors red, green and blue, designed for color reproduction in electronic systems (TV, monitor, scanner, digital camera, etc.). Digital recording systems use one or more electronic sensors, called CCD or CMOS, to “decompose” visible light through color filters to be captured by a patterned array of 3 pixels (photo-sites) each sensitive to only one RGB wavelength (650 nm, 510 nm, and 475 nm approx., respectively). More information > In the case of professional 3-CCD video cameras, these break the light down through a dedicated sensor for each wavelength.
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SD	Tokina designation for optical elements using low dispersion glass (see objective/optics, ED).
Sensor	Light-sensitive RGB semi-conductor chip, used in digital cameras, scanners, camcorders, etc. (See CCD/CMOS). Sensors come in a large variety of sizes, from 45x60 mm and larger (MF) to the tiny 1/2.5" (5.76x4,29 mm) models used in many P&S cameras. More information>
Sharp/Sharpness	Refers to the sensation of focus and the amount of fine detail contained in an image or rendered by a lens. An image can be crisp (sharp) or blurry (unsharp) and – in the case of lenses – we speak of sharp or unsharp in reference to their ability or inability to render crisp, clear images with large amounts of well-defined fine detail. Generally speaking, the sharpest lenses are almost without exception also the most expensive.
SLR	Single Lens Reflex camara. More information (Also see DSLR). Uses a mirror and a (penta) prism to project the image to be captured in an eye-level viewfinder. The difference with a “viewfinder / rangefinder” camera (with the viewfinder next or above the lens) and mid-format cameras (with waist-level viewfinders which project an inverted image), SLR cameras have the advantage to allow the photographer to compose the scene and measure incident light through the mounted lens (see TTL). The other benefit of the eye-level viewfinder is that external light is shut out, while composition is more precise, because the photograher is composing based on the focal length of the mounted lens, and - thus - sees what the film or sensor "see" at shooting time. More information
Petal-shaped sunhoods. For a tele-lens (top) and wide-angles (bottom)
Sun Hood	Lens– or sun-hoods are mounted to prevent the ghosting and flare that may occur when shooting at a critical angle against the light, or with the sun just at the edge of the image frame. Wide-angle lenses are particularly sensitive to this phenomenon, even though it is generally recommendable to use sun-hoods on all lenses, especially in broad daylight. It does not affect their operation and avoids the before mentioned annoying optical effects, which may not always be observed in the viewfinder. Most IF lenses come standard with petal shaped lens hoods, which can be deeper, shade a lens’ front element more effectively from stray light rays and are, therefore, better in combating ghosting and flare without producing the feared vignetting.
SWM	Silent Wave Motor. Quiet internal focusing motor, built into professional Nikon AF-S IF lenses. Economical AF-S models lack both IF and a silent wave motor.
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TC	Tele-Converter. Adapter ring that multiplies a lens’ focal length, typically by 1.4, 1.7 or 2, usually sacrificing 1-2 EV (diaphragms) of maximum aperture. Tele converters can also cause optical quality degradation – most notably contrast – apart of being an additional source of chromatic aberration, especially the more economical models.
TTL	Through The Lens. Exposure metering system that measures incident light through the lens, first used in the Topcon Super D (1963). The first Nikon camera with TTL was the F Photomic T, introduced in July 1965. An improved version of this system,  introduced in the late sixties and used in all modern SLR cameras, measures light at maximum aperture (f/max. of the attached lens), and determines the correct exposure at the selected aperture through a diaphragm indexing system (AI). Since TTL measures the light that effectively enters the camera on the focal plane, it is much more accurate than separate incident light meters or other systems that do not meter through the lens, especially for flash photography. Modern flash systems, such as iTTL no longer rely on sensors on the focal plane, but use pre-flash to determine correct exposure.
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Viewfinder	Small window in – or on top of – the camera body, which allows the photographer to compose an image. In SLR cameras, the viewfinder shows exactly (or almost exactly) what the camera is about to capture, because it redirects the lens’ projection on the focal plane (film, sensor) to the viewfinder, using a reflex mirror placed at a 45º angle in the lens’ projection path, a focusing screen and a pentaprism. Modern SLR camera viewfinders show a host of other information, such as shooting speed, ISO, aperture, focus, etc.
VR	Vibration Reduction. Nikon designation for its proprietary image stabilization system built into a lens or (P&S) camera, targeted at electronically reducing the effects of horizontal (pitch) and vertical (yawn) movements when using a camera handheld. (See also OS). Works well with long and heavy lenses with relatively small maximum apertures (f/4 and smaller), where it gives the photographer up to 3 EV (stops/diaphragms) latitude in circumstances where a lens without this system would need a tripod or at least a monopod to avoid camera blur (shake). However, the latest clean high ISO Nikons may allow up to four stops of latitude by raising ISO - up to 1600 (or even more). This is why investing in VR is worth careful consideration, taking into account that VR lenses are more expensive, heavier, technically more complicated (hence: more vulnerable and expensive) and that VR apparently is still not 100% free of “childhood diseases”. Despite this, VR has become so popular that it is used as a selling proposition, even for lenses that do not need it at all, such as – for example – the AF-S DX NIKKOR 18-55mm f/3.5-5.6 GII, which weighs in its non-VR version only 265 grams while measuring less than 8 cm. long. Principles of VR >
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Zoom	Lenses of variable optical length. Zoom also refers to the action of modifying the subject’s Image Measure by varying the optical length of a lens: zoom in/out. Zoom lenses have been considered inferior in quality compared with the primes (single or fixed focal length), which is not necessarily true. Nikon MF Zoom classics are the 35-70 mm, 35-135 mm and 70-210 mm, however, with the advent of the DX sensor – and its 1.5x crop factor – increasingly shorter lenses have appeared. The typical standard kit lens today is the 18-55 mm. f/3.5-5.6G (27-82.5 mm. equivalent), however manufacturers offer a very wide range of alternatives. Extreme wide-angle: 10-24, 11-16, 12-24; wide-angle to medium: 16-35, 16-80, 17-35, 18-70, 18-105, 18-135; wide-angle to tele: 18-200 or even 18-250 (13.8x). In the high-power zoom segment there is also a wide range of choices: 55-200, 70-200, 70-300, 80-400, 200-400, 50-500, 150-600, 200-500, 300-800 and even 400-1000 (200-500 with a dedicated 2x TC)
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