Glossary of Photographic Terms
This Glossary is being provided to give you a short description of the term and if applicable, a reference to a lesson which more fully describes the term. Most photographic terms are defined in a lesson. Sometimes those terms are used in a lesson before they are defined or fully described in a later lesson. This Glossary is being provided to give you a short description of the term and if applicable, a reference to a lesson which more fully describes the term.
The names of some terms or camera features may vary because different organizations, groups or individuals in differing geographical locations or languages describe it differently.
This Glossary is a “Work in Progress”. If you have any suggestions, corrections etc., please contact us at: email@example.com.
18% Gray Standard – The natural world (rocks and plants etc.) reflects about 18% of the light which strikes it and absorbs the rest. All camera systems are designed with this 18% Gray Standard in mind so the average landscape scene will be properly exposed. See lesson DP-115C Light and Exposure.
A-D Converter – A device which changes an analog signal to a digital signals. The A-D converter in a digital camera changes the analog electrical signals created by the imaging sensor into a digital signal that can be used by the camera’s computer to create an image.
Aberrations – Are imperfections or distortions caused by light passing through a lens. Some of these include: Spherical, Coma, Chromatic and Field Curvature aberrations. See lesson DP-114C Lens Basics.
Aliasing – Diagonal lines running across a low resolution image may appear as a sharply defined jagged line instead of a smooth gradual gradient from one tone to another. This is called aliasing. Anti-Aliasing / Low Bypass Filters and computer smoothing techniques are used to smooth out aliasing and make the image look more natural.
Altitude – When used with regard to the position of the sun in the sky, it is the number of degrees the sun is above the horizon. The horizon is at 0° altitude. Directly overhead is 90° altitude. See lessons DP-220C Landscape Photography and DP-330C Where is the Sun for more information.
Aperture – The variable opening which is normally located within the lens, which controls how much light enters the camera. The aperture for most DSLR type cameras is normally controlled electronically from the camera. The physical size of the aperture relative to the lens focal length is expressed in f stops. See Lesson DP-110C Aperture.
Aperture Priority – This is a camera mode in which the photographer determines and sets the aperture value on the camera. Then when the shutter is pressed, the camera’s light meter measures the amount of light entering the camera through the lens. Then based on the light intensity measured by the camera’s meter, the computer in the camera calculates the shutter speed needed to create an image with an adequate exposure.
Apochromatic Lens Element – A lens or a group of lenses in the lens assembly which are designed to focus all wavelengths of light on one point instead of at different points. Chromatic aberrations cause different wavelengths of light to focus at different distances from the lens resulting in color fringing. Apochromatic lens elements are designed to correct or reduce this issue. See lesson DP-114C Lens Basics.
ASA Rating – See ISO
Azimuth – Azimuth bearings or directions are part of a spherical coordinate system used to indicate a direction from a particular location or point. Compass bearings are often referred to as Azimuth headings or bearing. See Lesson 330C Where is the Sun for more information.
Aspect Ratio – The aspect ratio is the ratio between the longer and shorter side of an image or camera sensor. For example: The aspect ratio of an 10×8 inch image where 10 inches is the horizontal length and 8 is the vertical length is 10/8 or represented in a decimal format the ratio could be displayed as 1.25. The ratio of a popular HD image size could be 1920 x 1080 pixels or its ratio could be expressed as 1.777.
Aspheric Lens Element – This a lens element which has less curvature at the edges than at the center of the lens. These pieces of glass are often added to a lens to correct aberrations and distortion.
Asset Management – Refers to storing, labeling, rating, culling, categorizing, sorting and finding / retrieving your images. This issue becomes more important as you capture more images. Specific pieces of software (such as Lightroom) have been designed to help photographers “manage” their images.
Auto Focus – There are a number of in-camera systems which are used to automatically focus the camera’s lens system. The two most common auto focus systems are Phase Detection and Contrast Detection. These systems may use one or more Auto Focus Points to establish the focal point of the image. Some Auto Focus systems are designed to follow and focus on moving subjects. See lesson DP-111C Focus.
Bokeh – This is a Japanese term loosely translated as “pleasing blur”. It is often noticeable in the highlight areas of an out of focus background as a round bright spot with smooth gradients which blend into the other parts of the background. The round shape is caused by the number and shape of the aperture blades. Some lenses are designed with more blades and with curved aperture blades to form a better circle. Also, lenses set at smaller f stops will normally produce a more perfect circle.
Camera Buffer – This is the internal memory within your camera which temporarily stores your captured images as they are being sent to your camera’s storage media (i.e.: Compact Flash, SD card etc.) Your camera has a buffer because it can generate more image data when you are capturing a rapid sequence of images than a media storage card can write or store in any given period of time. The size of this buffer determines how many sequential images you can take before your camera has to stop and wait for the media card to catch up. See Lesson DP-106C Camera Electronics.
Color Profile (ICC Profile) – Color Profiles provide a standardized color management system to allow all digital devices to communicate accurate consistent color information from image capture to image printing or display.
Bracketing – In photographic terms, bracketing is the capturing of a series of images, often at different exposures. For example, you might capture 3 images of a scene, where one image is 1 stop under exposed, the next image is set at what the camera considers a good exposure and the last image could be shot 1 stop over exposed. You could compare the three images and select the one you like best. Bracketing is also used in High Dynamic Range (HDR) photography.
Camera Head – This is a device which attaches to a tripod or monopod to control the position or orientation of your camera.
Chromatic Aberrations – Are caused when different wavelengths / colors of light focus at different distances from the lens and thus some might focus in front of the sensor, some on the sensor and some behind the sensor. This results in an issue called “Color Fringing” which is most noticeable toward the edges of an image. See Lesson DP 114C Lens Basics.
Color Calibration / Color Management– This is the process of setting all of the components in your photographic workflow to the same color standard to allow you to get consistent output results. This allows you to get What You See Is What You Get (WYSIWYG) results where the image you just printed looks like the image on your monitor. The components in your photographic workflow will include the camera, scanner, monitor, printer, projector etc. Special software and equipment are available to calibrate your system.
Color Fringing – See Chromatic Aberrations
Color Space –Color space is sometimes called color palette, gamut. Color space refers to the range of colors that a photographic device, monitor, printer or other component can reproduce, display or print. Some common color spaces are Adobe RGB and sRGB. The Adobe RGB color space has a greater color range or gamut than does the sRGB color space. This subject will be discussed in a later lesson.
Color Temperature – Is a system of measuring the color of light emitted by different sources of light. Each light source is rated on a linear scale in degrees Kevin. (Degrees Kelvin a physics term used to measure temperature.) For example an incandescent lamp has a color temperature of about 2700 to 3000 degrees Kelvin expressed as 2700K. A candle has a color temperature of about 1850K. Midday bright sunlight has a color temperature of about 5500 to 6000K. Camera White Balance systems are designed to accommodate different light sources with different color temperatures to achieve natural or enhanced colors. See lesson DP-120C Reflected Light & White Balance.
Colorimeter – Is a hardware device used by color management systems to determine the color on a printed surface or a computer monitor.
Crop Factor – The crop factor is the term used to describe the lens multiplying effect when using a camera with an imaging sensor that is smaller than 24mm x 36 mm. See Lesson DP-107C How the Sensor Works.
Depth of Field – This is the area or portion of your image that is in reasonably sharp focus. Four major factors affect the Depth of Field. The size of the camera sensor, the focal length of the lens, the f stop you choose and the distance from the camera to the subject. The camera you are shooting with determines the size of the camera sensor. See lesson DP-112C on Depth of Field.
Diffused Light – This is a quality of light issue where a broad or large light source illuminates or lights a smaller object from multiple angles resulting in minimal to no shadows. A large cloud is a good example of a diffused light source which creates an image with very few or only slight shadows without sharply defined edges. Fog is another example or a diffused light source. See lesson DP-121C Diffused vs Hard Light.
Diffraction – We know that light bends when it passes through glass. It also bends when it goes past an obstacle, edge or through a slit. This bending or scattering of light as it passes an edge is known as diffraction. Since you want a sharp focused image in photography, the scattering of the light is not a good thing. Diffraction occurs in a lens assembly as the light passes by the edges of the aperture. As the physical size of the aperture gets smaller (larger f stop number), you get more diffraction and thus a less sharp image. Wide angle lenses at larger f stop numbers tend to have more diffraction than longer telephoto lenses. Much of this softness can be removed through post process sharpening.
Diopter – This is a feature which changes the magnification of the viewfinder. It is used to adjust the view to a particular person’s eyesight. Some cameras use a rotary wheel and others use a slider to adjust the magnification. See lesson DP-104C Camera Body Exterior for more information.
Distortion – Occurs when straight lines in an image are not straight. The two main types of distortion are barrel and pincushion. Barrel distortion caused the image to bulge outward and pincushion caused the image to bulge inward. Mustache distortion is a combination of the two. Consumer level lenses tend to have more distortion, but some distortion can be corrected in post processing. See lesson DP-114C Lens Basics for more details and illustrations.
Dots Per Inch (DPI) – You will see this term used in printing. The higher the DPI, the higher the resolution or detail in an image. Normally, when printing on an ink jet printer a DPI of 240 to 300 will provide adequate results. Some higher DPI settings may not yield better results. Some individuals may refer to computer monitor resolution as DPI when a more accurate reference would be Pixels Per Inch (PPI).
DSLR – Digital Single Lens Reflex Camera. This camera uses one lens to view and record the image. It has an internal mirror which moves up and down to redirect the light for image viewing or image recording. Reflex means “moving”. This type of camera differs from the Range Finder camera in that the Range Finder camera has two lenses. One lens to view the image and another lens to capture the image. See lesson DP-105C Different Types of Cameras.
Dynamic Range – This is the range of tones that a device can capture, display or print. Those tones range from very dark to very light. This dynamic range is often defined by stops of exposure. For example one camera may be able to capture 8 stops of exposure while another camera may be able to capture 10 stops of exposure. Having the ability to capture a wider or larger dynamic range allows you to capture more of the tones in an image which has very bright and very dark tones. If you try to capture a scene that has 10 stops of dynamic range with a camera that can only capture 8 stops of dynamic range, either the dark tones or bright tones will be clipped or lost.
EVF – This acronym often refers to an Electronic Viewfinder. Some cameras use Electronic Viewfinders to view the image before you take a picture instead of using a mirror with a penta prism or penta mirror. Some compare looking at an EVF to looking at a small TV or computer display of the image to be recorded. It is similar to your LCD monitor but it is smaller and shielded from ambient light so it is easier to see. They have some advantages over optical viewfinders and a few negatives.
EXIF Data – This is the technical data the camera records about the image. It normally includes the exposure information (Aperture, Shutter Speed, and ISO), Image name, the camera that was used to capture the image, the lens that was used and the focal length of the lens at the time of image capture, the time and date when the image was taken and much more. See the lesson DP-125C Metadata.
Exposure Bias – This term is sometimes used in programs such as Lightroom to describe Exposure Compensation. Exposure Bias is normally a negative or positive value above or below what the camera thinks is an adequate exposure. See lesson DP-118C Exposure Compensation.
Exposure Compensation – Not all scenes which a photographer encounters reflect 18% of the light back to the camera. (See 18% Gray Standard). Scenes which are very dark or very light will fool the camera’s metering system. Exposure Compensation systems are designed to allow the photographer to compensate or adjust the exposure controls for scenes which don’t reflect 18% of the light into the camera. See Lesson DP-118C Exposure Compensation.
f stop – This refers to the relative size of the aperture. It is often represented as f/2.8 or f/11. Your camera may only show it as 2.8 or 11 without the f/. The formula for f stop is:
f stop = the Focal Length of the Lens (mm) / the physical diameter of the aperture within the lens (mm). The f stop is a ratio whose number increases as the physical size of the aperture decreases and visa versa. For SLR type cameras, the f stop range may vary from about f/1 to f/36, depending on the lens. Many consumer level lenses have f stop ranges from about f/4 to f/22. See lesson DP-110C Aperture.
Far Focus Limit – The Far Focus limit is the farthest point of an image which is in reasonably sharp focus. It is the far limit of your Depth of Field. See lesson DP-112C Depth of Field.
Fast Lens – Lens with an f stop of f/2.8 or smaller (i.e.: f/2.0 or f/1.4 etc.) are considered Fast Lenses since they have larger physical apertures which allow more light to enter the camera. This greater quantity of light allows a FASTER shutter speed. Thus the term “Fast Lens”. Fast lenses help eliminate or minimize camera movement induced motion blur in low light situations when you can’t use a flash. A good place to use this might be in a play, concert, birthday party etc. See lesson DP-110C Aperture.
Fill the Frame – A term which is often used to encourage a photographer to have the subject take up a large portion or percentage of the image.
Filters – Are extra lens elements that are attached to the lens or inserted into the lens to modify the light in some way. Some filters, known as neutral density filters, reduce the amount or quantity of lighting striking the sensor. Other filters modify the color or increase saturation and contrast. Others, such as star filters, make any lights in the scene look like a star with lights emanating from the bright spot.
Flare – (or Lens Flare) is the unwanted scattering of light in a lens which leads to randomly located light artifacts and areas of low contrast in an image. This situation often occurs when a bright light source is located within the lens field of view or the bright light source could be located just outside the lens field of view.
File Compression – Some computer file types are designed to compress the data in a file to reduce the file size and allow more images to be placed on a storage media card. There are two types of compression, “lossless” and “lossy”. Lossy formats lose detail while lossless file compression loses very little if any detail. JPG file formats are lossy file formats.
Flash – Flash units or strobes are a type of lighting which creates a very bright, short duration light suitable for photography. There are portable and studio flash units. Portable flash units are sometimes called Speedlites, Speedlights or a similar term. Portable flash / Speedlights are often mounted on the hot shoe of the camera. Studio flash units are often called strobes. Strobes are usually more powerful lighting units powered by AC power. Some newer strobes have large batteries to allow their use in remote locations. Flash will be covered in a later lesson.
Flash Recycle Time – This is the time it takes for a flash unit to recharge the internal capacitor after a flash discharge or firing to be able to fire again. Or put more simply, the time between one flash and the next flash. Many flash units will take a second or two to recharge after a full power discharge. The state of the flash unit’s batteries have a large impact on the Flash Recycle Time. Batteries with a low charge take longer to recharge the flash. New batteries or large battery packs will recharge the flash more quickly. Flash Recycle Time is an issue when capturing multiple images at high frame rates. If your camera is creating images at a frame rate of 5 images per second and the flash takes 1 second to recharge, only one out of 5 images will be properly exposed each second.
Flash Synch Speed – This term is used to describe the fastest shutter speed that your camera will allow in most shooting modes when using a flash to light a scene. Shutter speeds faster than this will usually result in part of the image being under exposed.
Focus (in Focus) – is a term which describes the bending of light so that all of the light rays converge on one sharp point thus creating a sharp image. Out of focus would mean the light rays do not converge at one point and the image is blurry. See lesson DP-111C Focus and lesson DP-114C Lens Basics.
Focus Ring – is the ring or mechanism on most lens bodies which allows you to manually focus or defocus the light. See lesson 114C Lens Basics.
Focusing Screen – This is a component found in DSLRs and SLRs which helps focus the image when the image is viewed through the camera’s viewfinder. The focusing screen is often located just below the penta prism and is made of a translucent material. Some focusing screens are interchangeable and have etched markings with focus points, rule of third lines etc. See lesson DP-105C Different Types of Cameras.
Four Thirds Camera System (4/3) – This is a newer and smaller camera system developed by Olympus and Kodak. Other companies such as Panasonic and Fujifilm also manufacture cameras with this new format. What makes this camera format different is the size and aspect ratio of the image. Instead of using an aspect ratio of about 1.5 as most digital sensors use, this system uses a sensor which is 17.3×13 mm with an aspect ratio of 1.33. This smaller sensor allows the camera and its’ associated lenses to be much smaller in physical size and less expensive.
Frame Rate – This is a term which refers to the number of frames or images a camera can capture each second. Some cameras are designed to capture action scenes and have higher “Frame Rates” than other cameras. Higher or faster frame rates will capture more action.
Hard Light – Refers to a light source which is comparably smaller than the subject being illuminated. This type of light source normally causes “hard” or distinct shadows. The Sun is an example of a hard light source. See lesson DP-121C Diffused vs Hard Light.
HDR – High Dynamic Range (HDR) often refers to an image which is created from multiple images of the same scene with different exposures. These different images are processed using tone mapping software to extend the range of tones which are captured and displayed to a viewer or print. HDR images often eliminate or minimize the loss of detail often found in single frame images of scenes where you have a combination of very dark and very light portions of the image.
Hand Held – is a method of holding the camera with your hands while capturing an image. In addition to hand holding the camera you can mount the camera on a tripod or monopod. Hand holding the camera can result in some motion blur being introduced into an image at slower shutter speeds. See Lesson BDP-113C Shutter Speed for examples of different ways to handhold a camera.
Highlight Alert – This is a feature on the LCD monitor on many cameras which shows the portions of an image which have lost detail in the highlight portions of the image. Digital photography should expose to preserve the highlights. See lesson DP-116C Histograms and Highlights.
Histogram – A graphic representation of the distribution of tones in an image. The tonal range varies from 0 to 255 or a total of 256 possible tones. 0 is black without any detail and 255 is white without any detail. See lesson DP-116C Histograms and Highlights for more information and examples.
Hot Shoe – This is feature which is included on most cameras which provides a place to mount and control an external flash unit. It is normally located on the top of the camera and is sometimes used to mount other camera accessories. See lesson DP-104 Camera Body Exterior.
Hyperfocal Distance – Is a calculated distance based on lens optics which allows you to maximize the Depth of Field (DOF) in an image. It is often used in landscape photography. The Hyperfocal distance is based on the chosen f stop and focal length of the lens. Most DOF calculators will calculate the Hyperfocal distance. The DOF will extend from a distance of 1/2 of the Hyperfocal distance to infinity. See lesson BDP-112C Depth of field for more information and an illustration.
Infrared Light – Infrared light is wavelength of light that is not visible to the human eye. Even though it is not visible to the naked eye it can affect your photography. Most digital cameras have an infrared filter just in front of the imaging sensor to minimize this type of light. Some cameras are manufactured to just capture infrared light. Your camera can be modified to record infrared light but the change is irreversible and should be done by a company specializing in this type of modification.
ILC – Interchangeable Lens Compact camera. This is a newer category of camera which many consider an intermediate step between a “point and shoot” camera and an SLR. They have more features than a “point and shoot” camera and have a detachable lens. Their feature set is normally not as robust as that found on an SLR. Most of these cameras are mirror less and you must view the image on the LCD monitor before capturing the image.
Image Stabilization – This is Canon’s version of Vibration Reduction. See Vibration Reduction.
Ink Jet Printers – These are the most popular types of consumer printers because of their low initial cost and excellent image quality. Images are created by accurately spraying small droplets of ink to specific locations on a print.
ISO – Refers to a system of measurement used originally to determine a photographic film’s sensitivity to light. This photographic film measurement standard was adopted by the International Standards Organization (ISO) in 1974 and thus the name, ISO. A photographic ISO rating of 100 was often considered a baseline for outdoor photography. Higher ISO ratings were used for indoor photography or taking pictures in low light situations. An ISO of 400 or 800 was often used indoors. An ISO of 200 was twice as sensitive to light as ISO 100. An ISO of 400 was twice as sensitive to light as an ISO 200 and 4 times as sensitive to light as ISO 100. A similar approach has been taken by digital cameras to help photographers take handheld images in places with low light levels without the use of flash systems. Each doubling of the ISO standard in digital photography increases the cameras “sensitivity” to light by amplifying the electrical signals coming from the camera’s imaging sensor.
JPG Files – are files of stored digital information (such as a photographic image) which have been compressed to reduce their size. These files are compressed using a program approved by the Joint Photographic Experts Group (JPG). When JPG files are compressed, some of the original image data is thrown away in an effort to reduce the size of the file. This lost data cannot be retrieved and will result in some loss of detail in the image, depending on the amount of compression that is applied. See lesson DP-106C Camera Electronics.
Latitude – Latitude lines are part of a geographical coordinate system originally developed as navigational aids. These lines provide information about how far a geographical point or location is north or south of the equator. Longitude lines are not physical lines. They are imaginary east west lines which extend around the earth parallel to the equator. See lesson DP-330C Where is the Sun for more information.
LCD Monitor – is a device, usually located on the back of the camera facing the photographer, which is used to view information and thumbnails of the images you have captured or are about to create. It provides access to menus and internal camera programs to change camera settings and operating parameters. LCD stands for Liquid Crystal Display. Some LCD monitors can tilt or swivel to allow the photographer to view image when the camera is in an awkward position. See lesson DP-104C Camera Body.
LDR – Low Dynamic Range imagery is normally a single image which has been tone mapped to increase the available detail and to increase the dynamic range.
Lens – The lens is a device comprised of various pieces of translucent material which bend or refract light. Lenses are used to accurately focus light from the outside world onto a digital sensor or film to create a photographic image. Normally the refracting material is high quality glass mixed with various compounds to enhance its’ light bending capabilities and reduce certain defects or aberrations. Some less expensive lenses have plastic lens elements. Lenses are often rated on the amount of distortion, sharpness and contrast they exhibit. See Lesson DP-114C Lens Basics.
Lithium-Ion Batteries – Batteries are an important part of any camera system. Most cameras come with rechargeable batteries. At this point in time, Lithium-Ion batteries are the most commonly used types of batteries for mobile devices including cameras.
Longitude – Longitude lines are part of a geographical coordinate system originally developed as navigational aids. They provide east west information about a geographical point or location. Longitude lines are not physical lines. They are imaginary north south lines which extend from the North Pole to the South Pole. See lesson DP-330C Where is the Sun for more information.
Megabyte – The amount of information stored in a digital file is often quantified by the term “bytes”. Over time file sizes have grown from Kilo (1000) bytes to Mega (1 million) bytes. Thus, one megabyte is one million bytes of electronic data and 10 megabytes is a file with 10,000,000 bytes of information or data.
Metering – Internal camera metering systems are designed to measure the intensity of reflected light entering the lens. Off camera or external metering systems can measure the amount of light falling on a subject and not just the light being reflected by the subject. These are called incident metering systems. Some internal camera metering modes look at different portions of the scene and average the light measurements to help the camera determine an adequate exposure. Others metering modes measure the light intensity from just one small portion of the scene. See lesson DP-117C Metering.
Mirrorless Camera – This is a type of camera which does not have a mirror to redirect the light coming through the lens through a penta prism or penta mirror and into the viewfinder. Instead the light is directed toward the sensor which records a pre image and displays that image on an Electronic Viewfinder. There are various versions of this type of camera. Many of these cameras have detachable lenses.
Moire – Is the creation of a third or phantom pattern caused by the capture of an image with a distinct repeating pattern onto a sensor with a pattern of sensor elements. Anti Aliasing filters are placed in front of the camera’s sensor to minimize or eliminate these patterns.
Monopod – This is a term used to describe a vertical pole camera support system used to steady the camera. There is a bolt on the top of the monopod to attach a camera or camera head.
Motion Blur – This is blur which is introduced into an image by movement of the camera, the subject or both. Some motion blur can be eliminated by immobilizing the camera on a tripod or other device. Fast shutter speeds will also eliminate or minimize motion blur. Panning with a moving object may remove or lessen motion blur from the moving object but leave motion blur in the background. See lesson DP-113C Shutter Speed for more information.
Native f stop – the smallest f stop a lens has is its’ native f stop.
For Example: A lens might have its’ smallest aperture set at a constant f/2.8 aperture across all focal length. This lens would have a constant native f stop of f/2.8. Some zoom lenses have variable native f stops where the smallest available aperture size changes as the focal length of the lens changes. See lesson DP-110C Aperture.
Near Focus Limit – This is the nearest point to you in an image which is in reasonably sharp focus. The Near Focus limit is part of the Depth of Field. See lesson DP-112C Depth of Field.
Nickle Cadmium or NiCad Batteries – These are an older type of rechargeable battery used in many portable devices. Due to a variety of problems, these batteries have mostly been replaced with newer battery types but they are still available.
Nickle Metal Hydride (NiMH) – These are a new generation of rechargeable batteries which have a much higher capacity than NiCad batteries.
Noise or Digital Noise – This is the introduction of colored artifacts or discolored pixels in a digital image. These artifacts are most common in the darker areas of an image. A number of issues cause noise but the most common culprits are higher ISO settings, heat buildup during continuous shooting in hot weather or in some cases when using live view for extended periods of time.
Out of Focus – This is portion of an image which is not in acceptably sharp focus. This area can occur in front of or behind the Depth of Field. See lesson DP-112C Depth of Field.
Over Exposure – This is a relative condition where the exposure is longer or brighter than the exposure recommended by the camera. Over exposure often results in a lighter or possibly blown out image where there is very little to no detail in the highlight areas of an image. Over exposure may be subjective if your intent is to create a lighter image.
Parallax – When you view the image through one lens and record the image through another lens you may get a different recorded image than what you see in the viewfinder. This difference is called a parallax. The difference between what you see and what you record becomes greater when the distance between the viewing lens and the recording lens becomes greater and also when you get closer to the subject of which you are taking a picture. For the most part, SLR cameras eliminate this problem because you are viewing the image and capturing the image through the same lens. Other variations of the parallax problem may occur when you rotate your camera to capture multiple images to stitch together as a panoramic image. See lesson DP-105C Different Types of Cameras.
Penta Prism – The prism which sits on top of the SLR body and redirects the light coming from the mirror into the viewfinder eye piece is called the Penta Prism. See lesson DP-105C Different types of cameras.
Photon – Is an elemental particle which is part of the electromagnetic spectrum and which is responsible for what we commonly refer to as light. See lesson DP-115C Light and Exposure.
Pixel – This is a short hand term for Picture Element. Picture Elements are the building blocks of your image. They are the smallest individual components of an image. Pixels are often related to the individual photosites on your camera’s imaging sensor. Each pixel can be assigned a tone or brightness, color (hue) and saturation level. When this mosaic is viewed as a whole or as a composite you have an image.
PIxelization – When you zoom into an image to where you can see the individual pixels, you will note that the smooth tonal gradients that you are used to seeing are no longer there. Instead you see individual squares which form jagged borders with zig zag lines etc. Due to the high resolution of most images captured by modern digital cameras you normally don’t see this. This effect may be more noticeable in low resolution jpg images.
Point and Shoot – This phrase often refers to simplistic cameras which have few controls and which produce great snap shot photos of people and places. They often have non detachable wide angle lenses with great depth of field. Point and Shoot cameras have limited creative features when compared to an SLR camera.
Point of Critically Sharp Focus – The point at which the image is the sharpest is known as the Point of Critically Sharp Focus. The sharpness in an image gradually decreases in front of and behind that point. See lesson DP-112C Depth of Field.
Polarizing Filters – Are normally used to enhance outdoor images. Some of their uses include making the blue sky bluer, increasing contrast and increasing saturation. They can also reduce glare and certain types of reflections.
Post Processing – This the image processing which occurs after the image is capture or created. Some post processing is done by the camera when a jpg file is created. A more effective method of post processing is done in a computer after the image is uploaded to the computer.
Prime Lens – A Prime Lens has only one focal length such as 50mm or 100mm. If you want to fill the frame with the subject when using a prime lens, you may have to move closer to or further away from the subject to get the composition you want.
Range Finder – A camera system which uses one lens to view the subject to be photographed and another lens to admit light into the camera to capture the image. These camera systems are usually less complicated than the DSLRs and thus are often lighter and less expensive. See lesson DP-105C Different Types of Cameras.
Raw Files – A Raw file is the unedited image data created by the camera’s sensor. This data can be processed in the cameras internal computer to create a compressed JPG file. Or it can be exported intact to the media card and processed later in your computer. Most professional photographers shoot in RAW file format and post process the file in their computer because all of the image detail is saved. Each camera manufacturer has their own Raw file format (i.e.: Canon – CR2, Nikon – NEF). Adobe has created a universal Raw file format know as a Digital Negative (DNG file name). See lesson DP-106C Camera Electronics.
Red Eye – Sometimes when you take a picture of a person with an on camera flash unit, the eyes of the person are red. This occurs because the light from the flash enters the eyes and bounces off the red blood vessels at the back of the eye. The closer the flash is to the center line of the lens, the more pronounced the red eye effect will be.
Red Eye Reduction Systems – Camera manufacturers often use a pre flash in their cameras with “On Camera Flash” to constrict the pupil in the eye to reduce or minimize red eye in photos. This pre flash occurs just before the main flash fires. A better solution is to use an “Off Camera Flash” unit such as a Speedlite to move the flash unit away from the centerline of the lens.
Remote Image Capture – This term is used to describe capturing an image without pressing the shutter button on the camera. Remote Image Capture may occur with a cable release, wireless transmitter or with your smart phone or tablet.
Saturation – Refers to the intensity of a color. For example: the color red could have a saturation range from light pink through dark red. Black and white image do not have any saturation.
Sensor – This is the device which captures the image and creates the RAW image data. The sensor turns light into an analog electrical signal. The computer in the camera then turns that analog electrical signal into a digital input which is converted into an image. The camera’s sensor is the heart of the camera. Different cameras have different sizes of sensors. The size of the sensor impacts a variety of camera features. See lesson DP-107C How the Sensor Works.
Shutter Priority Mode – This camera mode allows you select a shutter speed and the camera selects an appropriate aperture value. After you select the shutter speed and press the shutter release button, the camera’s light meter measures the amount of light entering the camera through the lens. Then based on the light intensity measured by the camera’s meter, the computer in the camera calculates and sets the aperture value needed to create an image with an adequate exposure.
Shutter Release Button – This is the button which starts the process to capture an image. When looking at the rear of the camera or when holding the camera to take a picture, the shutter release button is normally located on the upper right hand side of the camera toward the front. It is usually operated or pushed with your right index finger. This button is the last thing you push to take a picture AFTER you have input your settings and established your composition etc. See lesson DP-104C Camera Body Exterior.
Shutter Speed – The camera’s shutter opens to expose the camera sensor to the light being focused on the sensor by lens. The amount of time the shutter is open, exposing the sensor to the light from the scene, is called the shutter speed. The shutter speed might vary from 30 seconds to 1/8000 of a second. See BDP-113C Shutter Speed.
SLR – Single Lens Reflex camera. The image is viewed and recorded through one lens. A moving (reflex) mirror is used to switch from the image viewing mode to the image recording mode. This system minimizes parallax errors and provides What You See Is What You Get (WYSIWYG) viewing and image capture. See lesson DP-105C Different Types of Cameras.
Speedlite or Speedlight – This is a term which is often used to describe an external flash unit attached to the Hot Shoe on the camera. These types of flash units are portable and can be used in remote locations where there is no AC power. See Flash.
Spherical Aberrations – When a light ray strikes a lens near its’ edge it is refracted or bent more than if it struck the lens near the center of the lens. This results in an aberration where the light striking the lens near the edge is not properly focused. This issue is often corrected with an Aspherical lens element. See lesson DP-114C Lens Basics.
Stop – In photography this term is used when describing exposure. It means to increase or decrease the exposure by a specified amount. The amount of increase or decrease is often specified in full stops. Many cameras will allow ½ and 1/3 stop increments in addition to full stops.
Increasing the exposure by one full stop allows twice as much light to strike the sensor. Thus your image will be twice as bright. Decreasing the exposure by a full stop allows half as much light to strike the sensor resulting in an image that is ½ as bright or darker.
The term “Stop” possibility has its’ origin with “Waterhouse Stops” which were used to control how much light entered the camera. These stops were plates with holes of various sizes which were inserted into the path of the light entering the camera. A plate which had a hole with a large cross sectional area, allowed more light to enter the camera compared to a plate with a hole that had a smaller cross sectional area. This is probably where the term “Stop Down” came from as you put in a plate with a smaller hole you reduced the amount of light entering the camera. See lesson DP-110C Aperture.
Strobe – This is type of flash unit normally used in photo studios. They are normally larger and more powerful than Speedlites. In the past, strobes used mostly AC power for power. There are a number of strobe units which now come with batteries to increase their use in remote locations. See Flash.
Storage Media – These are small electronic, solid state, memory devices which store the images captured by your camera. They normally plug into a slot in your camera. They come in a variety of sizes, types and capacities. Some of the types include SD cards, Compact Flash and others. Their storage capacities and write speeds have increased considerably in the last 10 years.
Thyristor – These are solid state electrical switches which are located within the flash housing. They control the electrical discharge of current to the flash tube to produce the bright flash we see.
Tiff Files – TIF or TIFF is Tagged Image File Format and is a popular file format used to create final, uncompressed images. Many software packages can create TIF files from other files such as RAW or jpg.
Tilt Shift Lens – These types of lenses simulate the capabilities of view cameras which were popular in the early 1900s. One of the most common tilt shift features that SLR photography utilizes is the tilt function which lets you control what is sharp in the image. The tilt function can be used to increase or decrease the Depth of Field beyond what is normally available on a normal lens.
Time Lapse Photography – This is the process of capturing multiple images at specific time intervals over a longer period of time. There are two main variables. The time between images and the total span of time to capture the images. Some cameras offer this feature as a menu item but extra equipment is often required.
Tripod – A camera support device with three legs to immobilize a camera to eliminate or minimize camera movement. This reduces or eliminates motion blur caused by camera movement. You often have the tripod legs and a tripod head or camera head as separate elements. Tripods are often used to record images shot in low light levels or with long shutter speeds.
TTL – This acronym refers to “Through the Lens” metering systems used on most digital cameras. These systems are very accurate because they measure the light that is about to strike the sensor after it has passed through any filters etc. attached to the lens.
Under Exposure – This term is a relative condition where the exposure is shorter or darker than the exposure recommended by the camera. Under exposure often results in a darker image where there is very little to no detail in the dark or shadow areas of an image. Under exposure may be subjective if your intent is to create a dark or low key image.
Vibration Reduction – Vibration Reduction is a system which is part of the camera lens or camera body which minimizes blurring caused by hand held camera movement. Movement is detected by gyroscopic sensors and dampened by electromagnets. These systems allow you to capture sharp images with a slower shutter speed than would normally be possible. Some camera / lens systems boast a 3 to 4 stop shutter speed reduction. Thus a shooting situation which would normally require a 1/200 of a second shutter speed might only require a 1/50 or 1/25 or a second shutter speed with a 3 or 4 stop shutter speed reduction. Camera manufacturers use different names for this function. Nikon (Vibration Reduction), Canon (Image Stabilization), Konica Minolta (Anti Shake), Sigma (Optical Stabilization), Tamron (Vibration Compensation), Pentax (Shake Reduction), Sony (Optical Steady Shot). See lesson DP-114C Lens Basics for more information.
Viewfinder – This is the device, screen or add on system used to view the image before it is captured. Most cameras have a built in viewfinder, but the viewfinder on some cameras is an add on. SLR cameras have optical viewfinders while some newer mirrorless cameras use Electronic Viewfinders. See lesson DP-104C Camera Body Exterior.
Vision – This is the term used to explain the process of coming up with an idea for an image. You create a vision of an image in mind. See lesson DP-150C Visualizing your Image for more information.
Vignetting – Is the darkening of the image around the outside of the image. It is more noticeable in the corners. This is caused by the design of the lens and is more noticeable in wide angle lenses and at smaller f stops. Some software programs, such as Lightroom, will allow you correct or enhance vignetting.
Watt Second – is a physics term used to denote the energy produced or used by object in a particular period of time. Thus one watt second indicates that an object consumed or created 1 watt of power for one second. This also equivalent to another physics term known as a Joule. One Joule of energy is equal to one watt second. The watt second term is used to denote how much energy is used to produce light from a studio flash unit.
White Balance (WB) – White Balance systems in a camera help you produce realistic colors when using different light sources with different colors of light. The White Balance system can help you modify the color of light to recreate the colors which naturally occurred in a scene. Or the WB system will allow you apply an artistic effect. See the lesson DP-120C Reflected Light and White Balance for more information.
Zoom Lens – This type of lens has a range of focal lengths to give the photographer the ability to create a composition without moving toward or away from a subject. The focal length range will vary. An example might be 24mm to 70mm or 100mm to 400mm. See lesson DP-114C Lens Basics.