Glossary
“So what does it all mean…?”
Photography can be a very technical business (or even hobby), so I thought I’d put together a list of all the major terms so that you can understand what’s going on - most of the time…!
Aperture
The aperture is the size of the ‘hole’ in the lens that allows light to pass through the camera to the film or sensor. It’s measured in ‘f-stops’, and these are simply the numbers you get when you divide the focal length by the diameter of the aperture. Because each stop has to be a doubling or halving of the light and because a doubling of the diameter doesn’t give you a doubling of the area of the aperture, you get ‘funny’ numbers like f/5.6 or f/7.1.
Aspect ratio
This is simply the ratio between the long side and the short side of an image, and most digital SLRs create a 3:2 image although 4:3 is also common. It can also loosely be used to describe either a landscape (horizontal) or portrait (vertical) format.
Back button focus
This is a trick used by most DSLR photographers to separate engaging the autofocus from taking the picture. The advantage is that you can maintain focus when taking a burst of images of a moving subject, and you can also ‘lock’ the exposure and focus and then reframe the image if you want to change the composition (or if the focus point is outside the central area in the viewfinder). To set it up, you need to go into the menu system and do two things:
Make sure that half-pressing the shutter doesn’t engage autofocus
Set the AE/AF Lock button to do it instead
Blue hour
This is the period of time either just before sunrise or just after sunset when the light tends to take on a blue cast. The exact duration depends on the latitude, though, so it may be much less than an hour.
Bokeh
This is a term used appreciatively for an out-of-focus background in a photograph, particularly when it contains blurred points of light that appear as circles. Having more ‘blades’ in the diaphragm that controls the size of the aperture means that these blurred areas are more circular, so ‘good bokeh’ is one measure of a good lens.
Bracketing
In situations where the lighting conditions are difficult or unpredictable, bracketing allows you to hedge your bets by taking the same shot at different exposure values. On most DSLR cameras, you can control most of the variables:
whether to change the aperture or the shutter speed
the difference between exposures (eg 1/3 of a stop or a full stop)
the order in which to take the images (eg darkest to brightest or the central one first)
the number of shots to take (eg the central exposure plus three, five or seven either side of it)
Bulb
Bulb or ‘B’ mode is a setting that allows shots to be taken using longer exposures than the camera offers automatically. Usually, the longest exposure on a DSLR is 30 seconds, but bulb mode allows any duration. Cameras vary, but you either press the shutter to start the exposure and lift off to end it or press the shutter twice, once at the start and once at the end. Given that the timing is manual, you’ll need to have a stopwatch or some form of timer to make sure the length of the exposure is accurate.
Burst rate
This is simply the number of shots you can take in any continuous shooting mode before the frame rate starts slowing down. Every image is stored in a ‘buffer’ before being written to the memory card, so the size of that buffer determines the number of shots it can handle. This might be around 50 shots in a typical DSLR, but one or two of the latest cameras have no limit to the buffer, which means you can ‘spray and pray’ for as long as you like!
Candid
A candid shot is simply one that is not posed, but in some cases the subjects may not even be aware they’re being photographed. This is an important distinction when planning a wedding, for instance, when the bride and groom might specifically ask for ‘lots of candid shots’.
Chimping
This is a derogatory term for checking almost every photo on the back of the camera while doing a shoot. Yes, it’s important to check the exposure and focus, but looking at the pictures obviously means less time for actually taking them, and you might miss a crucial moment. The word is derived from the ‘oohs’ and ‘aahs’ photographers make while chimping that sound a bit like the noises of a chimpanzee!
Chromatic aberration
Due to the different wavelengths of different colours of light, lenses cannot focus them all on exactly the same plane. This leads to green and purple or blue and yellow ‘colour fringing’ on the edges of objects in the picture, particularly where there is high contrast, eg if there’s a bird in the sky. It’s easily fixable in Lightroom by clicking the Chromatic Aberration checkbox, but you may have to go into the colour fringing panel and manually play around with the settings to get perfect results.
Clipping
White or black clipping happens when the image is either overexposed in the brightest areas or underexposed in the darkest areas and the sensor therefore fails to record any detail. People might also say that the highlights are ‘blown out’.
Composite
This is simply a combination of multiple images into one. It can either be done through multiple exposure in camera or by using Photoshop to create different layers and ‘painting' over certain parts to make them appear or disappear.
Composition
This is simply the arrangement of the elements in a photograph. Good composition is one of the keys to good photography, and various rules of composition have been developed (or borrowed from the art world) in order to make life easier, including framing, leading lines and the rule of thirds.
Contrast
Contrast is the range of tonal values in a photograph, from the brightest areas to the darkest. Digital images normally need a boost to the contrast in order to make them ‘pop’, and this can easily be done by moving the Contrast slider in Lightroom or playing with the Whites and Blacks sliders in order to control both elements individually.
Crop factor
The crop factor is the number you get when you divide the diagonal distance from corner to corner of a 35mm camera’s sensor by the equivalent measurement in another camera format. For example, a DSLR has a 36 x 24mm sensor, so the diagonal is 43.27mm long. The Nikon CX sensor is 13.2 x 8.8mm with a diagonal of 15.86mm, so the crop factor is 43.27 divided by 15.86, or 2.73 (rounded to 2.7). This number is useful as you can multiply it by the length of any lens on a crop format camera to get the equivalent focal length on a 35mm camera. For instance, a 300mm lens on a CX format camera is the equivalent of a 540mm lens on a full-frame DSLR as 300 x 2.7 = 540. This might be seen as a ‘good’ thing, but what’s really happening is that the same image is just being cropped so you don’t see as much of it in the final photograph. Crop format cameras may be cheaper and lighter, but that comes at the expense of fewer pixels, which means image size and quality both suffer.
Depth of field (DOF)
This is the distance between the nearest and furthest objects in an image that are acceptably sharp. Typically, a third of this zone will be in front of the focus point and two thirds behind it. To increase the depth of field, you have to do any or all of these things:
close the aperture (eg f/8 rather than f/5.6)
use a wider angle lens (eg 50mm rather than 100mm)
increase the distance to the subject
To reduce the depth of field, you simply have to do the reverse.
Diaphragm
This is the part of the lens that controls the aperture. Modern DSLR cameras have what’s called an ‘iris diaphragm’ that has a number of overlapping blades that swivel open and shut in order to create the required f-stop.
Dynamic range
This is the range of light values between the brightest and the darkest, measured by stops or Light Values (LV). Strictly speaking, this refers to the scene in the real world rather than the image in your camera, but most people use it for both. Note that digital cameras generally have a slightly lower dynamic range than film cameras, but both are beaten by the human eye.
Compact cameras: 5-7 stops
DSLRs: 8-11 stops
Human eye: 10-14 stops
EXIF
EXIF stands for the EXchangeable Image File format, which is a standard for images, sound, and tags used by digital cameras, scanners and other devices. It’s mostly used to refer to a series of EXIF metadata fields. These cover basic information about each image, including the file name, pixel dimensions, date and time of capture and the shutter speed, aperture and ISO value. They’re created automatically, but you can also edit them in Lightroom or other software programs.
Exposure
This is the amount of light that reaches the sensor and thereby controls the brightness of the image. You can change your exposure by changing any or all of the elements in the Exposure Triangle:
aperture
shutter speed
ISO
Exposure compensation
This allows you to brighten or darken an image when the camera’s built-in meter is likely to be fooled (or just for artistic effect). Cameras are ‘told’ by the manufacturers to expect a scene with a tonal value of 18% - in other words, 18% of the light is reflected. That may be true in general, but it’s not going to be true if you’re shooting a black bear in the woods or a polar bear on the ice! On most DSLRs, there’s a dial that allows you to add or subtract exposure compensation in increments of 1/3 of a stop in order to cope with similar situations. Just remember which way it works:
The camera will try to underexpose a bright scene, so you’ll positive exposure compensation.
The camera will try to overexpose a dark scene, so you’ll need negative exposure compensation.
To give you an idea, you shouldn’t ever need more than a couple of stops of exposure compensation in either direction.
Exposure Value (EV)
This has a couple of different meanings:
A number that represents the same exposure given different combinations of shutter speed and aperture value, eg 1/500 of a second at f/11 or 1/1000 of a second at f/8
An interval on the photographic exposure scale, with 1 EV representing either a doubling or halving of the exposure
F-stop
See Aperture.
Fast
A lens is fast if it has a wide maximum aperture such as f/1.8. ‘Fast’ lenses are especially useful in low light and for generating good bokeh due to the lower depth of field.
Flare
This is stray light that creates interference in the image in the form of bright circles, haze or desaturation, particularly when shooting into the sun. It can be quite fashionable, and you can even create it yourself in Lightroom by using a radial filter angled in from one of the top corners of the image.
Focal length
This is basically the length of the lens, which determines the magnification and field of view (FOV), but it’s not quite that simple. Modern lenses have lots of different elements, and telephoto lenses even have concave lens elements that make light rays diverge rather than converge in order to reduce the overall length of the lens, so the focal length is hard to work out and is rarely the actual length of the lens. In fact, what focal length really means is ‘effective focal length’. That is a simplification that assumes the lens is actually the pinhole in a pinhole camera, and the focal length is just the distance from that to the image on the back of the camera. Anyway, the important point here is that the longer the lens, the more magnification you’ll get. As a rough rule of thumb, you can work it out by dividing the focal length by 50mm - which is approximately the same focal length as our eyes. Thus, a 400mm lens has a magnification of 400 divided by 50, which is eight. Lenses are produced with all kinds of focal lengths, but the basic groups are the following:
wide angle: less than 35mm
standard: around 50mm
medium: 70-135mm
long (or ‘telephoto’): from 135mm all the way to 800mm
Frame rate (FPS)
This is the number of pictures that a camera can take in one second and is therefore expressed as Frames Per Second, or FPS.
Full frame
A full frame DSLR has a 35mm sensor (36 x 24mm).
Glass
This is a common term for the lenses people own.
Golden hour
This is the period just after sunrise or before sunset when the sun is near the horizon, leading to ‘warmer’ light that is redder than normal.
High Dynamic Range (HDR)
HDR images try to reproduce more of the bright and dark areas of a scene by combining multiple images at different exposures. The brighter areas are therefore darkened, and the darker areas are brightened in order to retain detail.
Histogram
Histograms appear on the back screen of DSLRs and in the Develop panel in Lightroom. They are simply frequency charts showing how many pixels in an image correspond to a given light level. The darkest values are on the left, and the brightest values are on the right. The usual histogram is in black and white, but you can also have histograms that show the primary colours of red, green and blue (RGB). Histograms help to show the real brightness of an image in a convenient and standard visual form. This avoids problems caused by the differing brightness levels of monitors and LCD screens.
Hyperfocal distance
The concept of the hyperfocal distance allows photographers to keep as much of the scene as possible in focus right up to the horizon. Simply put, if you focus on a point at the hyperfocal distance, everything from half that distance away to the horizon will be acceptably sharp. Some people call the near point the hyperfocal distance, but that’s just confusing!
Image Stabilisation (IS) or Vibration Reduction (VR)
These are Canon and Nikon phrases to describe a system of stabilisation that allows you to take pictures at slow shutter speeds without having to worry so much about camera shake. The system can be found in either the lens or sometimes the camera body, and its effectiveness is measured in stops. For example, a lens with IS/VR might have two stops of vibration reduction, meaning that you could take shots at 1/15 of a second rather than 1/60 without worrying about motion blur. When using tripods or at high shutter speeds, these systems are not necessary and should probably be switched off.
IPTC
IPTC stands for the International Press Telecommunications Council and is mostly used to refer to a series of IPTC metadata fields. You can edit these in Lightroom and other software programs to specify various pieces of information, such as the headline and copyright status of each image and the contact details of the photographer.
ISO
This is the standard measure of a sensor’s sensitivity to light. Conveniently, if you double the ISO, you also double the sensitivity, so that makes it easier to work out what it should be in certain situations. Confusingly, ISO doesn’t actually stand for anything. People sometimes assume it stands for the International Organization for Standardization in French, but that’s not true. The organisation refers to itself as the ISO, but they realised that any abbreviation would be different in English, French and many other languages, so they decided to go for something that sounded similar and had echoes of ‘isos’, which is the Greek word for equal.
JPEG (or JPG)
JPEG stands for Joint Photographic Experts Group, but it’s more commonly known as one of a few popular compression formats for photographic files. There is a loss in quality from RAW files, for instance, but the gains in convenience generally outweigh that loss except if you’re editing an image or you want to print it out in a large format.
Kelvin
This is simply the Centigrade or Celsius temperature scale rebased to start at absolute zero, or -273°C, so one Kelvin is equal to one degree Centigrade. It is mostly used in photography to measure the colour temperature of a scene, which is important in getting the white balance right.
Light meter
Light meters can be bought separately, but they are also built in to most DSLR cameras in order to measure the brightness of a scene. That reading can then be used to produce the best combination of shutter speed, aperture and ISO when the camera is set to one of the automatic modes (or when using Auto ISO).
Light Values (LV)
This is the unit used to measure the brightness of a scene. Here’s a quick list of some typical Light Values, courtesy of Ken Rockwell:
LV 18 and above: Bright reflection off a sunlit object, including reflections off the sea
LV 17 White object in direct sunlight
LV 16 Light gray object or skin in full sunlight
LV 15 Gray card in full sunlight; typical exposure for ugly front-lit noon daylight photos
LV 14 Typical light level for side-lit daylight shots in good afternoon light
LV 13 Typical shadow cast in a daylight scene; cloudy bright days
LV 12 California bright overcast
LV 11
LV 10 Dark, dreary overcast day in Boston, London or Paris
LV 9
LV 8
LV 7 Typical indoors; light outdoors about 10 minutes after sunset
LV 6
LV 5
LV 4
LV 3 Brightly lit night street scenes
LV 2 Typical night street scenes
LV 1 Dark scenes outdoors at night
LV 0 LV Zero is defined as the light level that requires a 1 second exposure at f/1 with ISO/ASA100 speed film.
LV -1
LV -2
LV -3
LV -4
LV -5 Scene lit by the full moon
LV -6
LV -7
LV -8 The Milky Way
LV -9
LV -10
LV -11
LV -12
LV -13
LV -14
LV -15 Scene lit only by starlight.
Macro
This is the term used to describe photographing small objects and animals. A ‘macro’ lens is a lens designed to take such pictures, and it will often produce images in which the subject appears larger than it is in real life.
Manual
This is the shooting mode in which the photographer chooses the aperture, shutter speed and ISO, thus retaining complete control over the exposure and ‘look’ of the image. Note that it’s also possible to shoot in Manual while using Auto ISO, which takes care of the level of exposure.
Metadata
This is the catch-all term for all the information carried by an image file that is not actually used to create the physical image. It includes so-called ‘EXIF’ data that is unique to a particular shot, such as the shutter speed, aperture and ISO, but it also contains general information such as copyright details that are automatically added to every image. One of the joys of digital photography is that all this data can be edited in Lightroom or similar programs.
Noise
This is the digital equivalent of ‘grain’ generated in images from film cameras. It is the unsightly and uneven blotchiness resulting from errors and quantum variations in the recording of the image on the sensor. It’s called ‘noise’ by analogy with the related concept in audio electronics, in which the ‘signal’ is obscured by unwanted ‘noise’ in radio broadcasts, for example.
Overexposure
Overexposure happens when too much light is allowed to hit the sensor due to a poorly chosen aperture or shutter speed or when the ISO is set too high. It simply means that the image is brighter than it should be.
Program mode (P)
This is a semi-automatic shooting mode that allows the photographer to make a few choices when it comes to white balance, ISO and the use of flash, but everything else is controlled by the camera. It’s a kind of half-way house between fully automatic and shutter priority (S or Tv) or aperture priority (A or Av).
Pixel
The pixel is the smallest unit of an image created with a camera. It is simply a dot with a uniform tone and colour. Manufacturers publicise the number of pixels (or megapixels) in their cameras’ sensors in order to give guidance on how detailed the images can be.
Portfolio
A portfolio is simply a body of work. In the bad old days, you’d have to print out all your best images and collect them in an enormous black leather binder in order to show them off to potential clients. These days, it’s much more common to use websites.
Prime
This is just another word for a lens with a fixed focal length - in other words, the opposite of ‘zoom’. Prime lenses tend to have a wider maximum aperture and produce better images, but at a higher price.
RAW
RAW files are image files that come straight out of the camera. The word is written in capitals just to follow the convention of writing other format suffixes in capitals, such as JPG or TIF. Every camera manufacturer uses its own proprietary RAW format (such as Nikon’s NEF), but there’s also a generic RAW format called DNG. The benefit of ‘shooting in RAW’ is that every possible piece of image information is collected, which makes it much easier to play around with the white balance, for instance. There is also generally no compression (unless you choose a compressed RAW format), which means no data loss. However, that comes at a cost in terms of the file size: the RAW file from a Nikon D850 camera can be up to 50MB!
Rear curtain and front curtain sync
These terms just describe when the flash fires:
Rear curtain flash fires at the end of the exposure
Front curtain flash fires at the start of the exposure
This is useful to know if you’re taking a picture of a moving subject such as a skateboarder. Rear curtain flash will put the blur behind (rather than in front of) your subject.
Resolution
This is simply the number of pixels on the sensor, and it can either be shown as the dimensions of the sensor (eg 8280 x 5520) or the product of those two numbers, which is the total number of pixels (eg 8280 x 5520 = 45.7 megapixels). Note that the maximum image size is usually a little bit less than this figure as some pixels are not used.
Saturation
This indicates the vividness of all the colours in an image. You can play around with the Saturation slider in Lightroom to control this. Increasing the saturation can improve the image, but just make sure it doesn’t look fake. Equally, you can reduce the saturation to achieve a ‘washed-out’ look or go all the way and reduce it to zero in order to get a black and white image.
Scene modes
These are automatic options available on compact cameras that are each suitable for a particular situation. Typically, they might include ‘Ski’, ‘Portrait’ or ‘Macro’.
Sensor
This is an electronic component of digital SLRs that replaces film and allows the image to be recorded. It consists of millions of individual pixels.
Shutter speed (or Time Value)
The shutter speed is the length of time that the shutter remains open in order to record the image on the sensor (or film). The faster the shutter speed, the easier the camera will find it to ‘freeze’ the action. The slower the shutter speed, the more motion blur will be introduced. Canon calls it ‘Time Value’ instead.
Spray and pray
This describes the actions of photographers who just take as many pictures as possible in continuous shooting mode and hope they get something good out of it!
Through-The-Lens (TTL)
This is a form of flash metering that works out the correct exposure by measuring the light bouncing off the subject that comes in through the lens.
Tonal range
This is similar to the dynamic range and represents the number of tones in an image, from pure black to pure white. The terms mean slightly different things but are often used interchangeably.
Underexposure
Underexposure happens when too little light is allowed to hit the sensor due to a poorly chosen aperture or shutter speed or when the ISO is set too low. It simply means that the image is darker than it should be.
Vibrance
This is a term invented by Adobe to refer to a saturation slider that only focuses on pixels that are not fully saturated. The benefit is that skin tones, for examples, don’t end up looking fake.
Vignetting
This is the darkening at the corners and edges of photographs that often occurs with wide angle or older lenses. Programs such as Lightroom can correct for this easily enough, but you might actually want to add a vignette deliberately in order to draw the attention of the viewer away from the corners and towards the subject.
Watermark
A watermark is a word, phrase or logo that photographers superimpose on their images in order to protect their copyright and try to avoid duplication.
White balance
This is the setting that tells the camera what colour the light is. There are usually a number of options to cover the most common situations:
Automatic
Incandescent: 3000K
Fluorescent: 2700-7200K
Direct sunlight: 5200K
Flash: 5400K
Cloudy: 6000K
Shade: 8000K
Custom
Note that the ‘warmest’ colours actually come from the coldest colour temperatures (and vice versa). This is simply because people associate blue with cold objects such as ice and red with warm objects such as an open fire.
Wide open
This is just another way of saying ‘using the maximum aperture’, in other words, letting as much light in as possible.
Zoom
This is just another word for a lens with a variable focal length - in other words, the opposite of ‘prime’. Zoom lenses tend to have a narrower maximum aperture and don’t provide such high optical quality, but they’re more convenient and generally cheaper.
Source: Wix Photography, Photography Life, Ken Rockwell, Digital Photography School, The Lens Lounge
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