Canon S3 IS

Translate camera lingo into meaningful information by using this glossary.

While I was writing my last tutorial, I suddenly realized that I am using idioms throughout my texts, the meaning of which may be elusive. Therefore, I decided to start this glossary to help you understand.

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I focused this “dictionary” on terms relevant to digital cameras.

AD Converter: The Analog to Digital Converter transforms the Sensor information (charge) into digital levels suitable for the digital processor.

AE Lock: The Automatic Exposure Lock holds the exposure settings (aperture, shutter) over a series of images. Panoramic stitches require locking exposure.

AF Servo (AI Servo): This keeps the focus on a moving subject. AF Servo is useful for sports and wildlife photography.

Aliasing: Refers to the stair stepping (jaggies) of diagonal edges in images when the resolution is too low.

Anti Aliasing: Technique to reduce Aliasing by softening of aliased edges through blending and averaging of pixel values. The resulting image will look smoother and more natural.

Aperture: The size of the lens opening that determines the amount of light hitting the sensor. F-Stops are a measure for Aperture. The aperture affects Exposure and Depth of Field.

aperture priority: In Aperture Priority mode, you will select the aperture and the camera will determine the correct shutter speed for the available light. The shutter speed will also depend on ISO Sensitivity. To control Depth of Field use this mode.

Artifact: These are unwanted image abnormalities like Chromatic Aberrations, Blooming, Moire, Noise, JPG Compression and others.

Aspect Ratio: This is the relationship of horizontal to vertical dimensions of images.

Autofocus: The camera will automatically focus on subjects in the image. Depending on the focus points, some subjects might not be “seen” by the focus system.

barrel distortion: This will cause images to look inflated near the center of each corner (like an old CRT TV). It usually occurs on wide-angle lenses and at the wide end of the zoom.

bit: Bits represent digital data in computers. Digital Images are made of bits. The Bit Depth refers to the amount of bits used for each pixel. A bit depth corresponds to 2^(Bit Depth) levels (e.g. 16.7 Million for 24-bit).

Blooming: When overexposed pixels affect adjacent pixels, we call this blooming. Please see my tutorial on how to fix Blooming for night scenes in Photoshop.

Burst Rate: During Burst, the Camera will take multiple shots after each other, as fast as it can. The Burst Rate is measured in frames per second (fps). The maximum number of pictures that can be taken during a burst mainly depends on the available camera memory and memory card speed.

CCD: Charge Coupled Device. Usually refers to an array of CCD cells used as a Sensor in Digital Cameras.

chromatic aberration:  As the lens focuses different wavelengths slightly differently, Chromatic Aberration occurs. One example is the purple fringing you often find around edges (e.g. leafs before a bright sky)

CMOS: = Complementary Metal Oxide Semiconductor. This refers to the technology in which today’s digital chips are fabricated. The technology is suitable for integration of image sensors together with digital processing units.

Color Space: A color space is attached to an image to determine how the image is represented (tutorial on color profiles)

Color Calibration: This is the process of matching the color of two or more devices through software and/or hardware (tutorial on Color Calibration)

Colorimeter: A device for measuring and calibrating color devices.

Compact Flash (CF): Compact Flash is a removable storage card format. It has the largest physical size of all competing memory card formats. Most digital SLR cameras use this format.

Digital (Signal) Processor (DSP): The DSP is a digital microchip that has been designed for special tasks (signal processing). In Digital Camera Systems, the DSP is handling all the image processing required.

Digital Zoom: Do not use this feature! Forget that you ever heard of this, seriously. This is nothing more than In-Camera Crop.

Depth of Field (DOF): DOF refers to the areas behind and in front of the main focal plane that are still sharp. DOF is thus highly subjective and depends on the final print size and viewing distance. A small aperture (large f-stop number) generally increases Depth of Field. More about Depth of Field is found in this Tutorial about DOF and HFD.

DPI (Dots Per Inch): A unit used to describe the resolution of scanners or output devices and also images (although PPI would be more accurate in this case).

Dynamic Range: Dynamic range is the ratio between the largest possible signal a sensor can output before it saturates to the lowest possible signal it can measure.

Effective Number of Pixels: Sensors have more pixels then are used for creating an image, since the data needs to be processed (e.g. bayer, anti-aliasing …). Most of these algorithms require information of neighbor pixels. The DSP crops the image and the resulting smaller image has the Effective Number of Pixels.

EXIF: The Exchangeable Image File header contains information about the image, the camera, location, date and time and camera settings.

Exposure: Exposure refers to the amount of light a sensor receives. It can be influenced by the aperture and shutter speed.

Exposure Compensation: This will use the cameras automatic exposure, but it will allow the photographer to increase or decrease the exposure by a certain amount, set by the exposure compensation value.

Firmware: The camera system consists of hardware and software. The software that runs the internal microprocessors is the firmware. It can be updated to fix bugs or add new features. Sometimes this is used to hack in new features (I did this on my Canon S3 and Canon Digital Rebel).

Focal Length: The focal length is a measurement (in millimeters) that determines how far from the lens the focal point (on the sensor) is. It will determine your field of view (wide angle, telephoto).

F-stop: Apertures are marked in f-stops, the larger the f-stop the smaller the aperture. Common numbers are: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32. Large and expensive lenses can achieve smaller numbers.

Histogram: Histograms represent brightness distribution in digital images. They are important to evaluate correct exposure. The height (y-axis) represents the amount of pixels and the x-axis represents the brightness value.

Image Stabilization: Image stabilization helps you taking handheld shots that would otherwise require a tripod by compensating for small and fast movements (shaking). It is especially useful on long lenses in less than ideal lighting.

Interpolation: Interpolation is a method of generating information from neighboring elements. It can be used when increasing images, where new pixels are interpolated or during the Bayer Interpolation to generate color information (from the RGGB matrix).

JPEG: This is the most common digital image file format. It is compatible with virtually all image editing programs and camera hardware. It offers a good compression and decent quality. Although there are rivaling formats, the widespread use of JPEG will make it very hard for them.

Lag Time: This is the time from pressing the shutter release until the camera takes the picture. A shorter lag time is desirable, especially for action photography.

LCD Screen (Liquid Crystal Display): Color LCDs have become a standard in Digital Cameras. They provide instant feedback and can display information such as histograms.

Macro: Macro photography is the ability to capture a subject at very close distance. Usually the size of the subject is at least 1:1 on the sensor (in 35mm terms).

Memory Card: Removable Storage used in Digtal Cameras.

Memory Stick: This is a Memory Card developed by Sony.

Noise: Statistical variations that are inherent to the sensor system cause Noise. Noise is always present, but higher sensitivities and smaller sensors (used in cheaper and smaller cameras) usually generate more noise.

Pincushion Distortion: This is the opposite effect to barrel distortion. It causes images to be pinched at the center. Usually this occurs at the telephoto range of a zoom lens.

Pixel: Digital pictures consist of pixels, the smallest units. Each pixel has a color, that can be represented by 8 or 16 bit or as a floating-point number (32bit HDR).

PPI: PPI=Pixels per Inch. This is often confused with DPI. Color printers use several dots to create a single pixel. This looks good on the specification of the printer, but it also confuses. PPI can be used to describe the actual Pixels per Inch of a Print.

RAW: A RAW is the image in its raw form, as it comes from the sensor. By processing RAW files on the computer instead of using the in-camera function, more degrees of freedom are available.

Secure Digital: This is one of the smallest Memory Card formats (besides XD).

Sensitivity (ISO): A higher sensitivity can be used to trade off low light performance for Noise. The sensitivity in terms of ISO standards has been introduced to imitate those of Film.

Sensor: The sensor converts photons (light particles) into electrons (electrical charge). More photons (brighter) generate more charge. Color filters placed in front of the sensor elements encode the color information, as the light sensitive elements are not color selective.

Sharpening: This is the process of increasing the edge contrast of an image. It does not increase detail, but only create the appearance of a sharper image.

Shutter Priority: In this mode, the photographer selects the shutter speed and lets the camera decide the correct aperture for the pre-determined ISO speed. This is used to blur water or freeze action in sports photography.

SLR: When you look through the viewfinder of a Single Lens Reflex (SLR) camera, you will look through the lens itself via mirrors and/or prisms. This has certain advantages preferred by many photographers.

Viewfinder: The viewfinder is the “eye-piece” that you look through to compose your shot.

Vignetting: Small long lenses can experience vignetting, which darkens the corners of the image. The barrel of the lens is responsible for this effect. In other words, the image circle your lens can project is too small for the sensor.

Zoom: Making an image larger (zooming in) or smaller. Zooming effectively lets you decide how much of a scene you wish to include in your picture.