The Book of Photographic Terms

A format of film designed for medium format cameras. The 220 is twice the length of the 120 giving more images per roll.

From tests conducted early in the development it was determined that the average scene reflects 18% of the light falling on it. Camera meters and other exposure devices use this as a standard for photographs. However, if an image is more or less reflective than this exposure compensation is required.

A card which has one surface a grey tone which is calibrated to be 18% reflective. This is useful to ensure exposure is correct. It is often used to calibrate the color temperature for color photography.

This describes an image, which is taken close to the camera; where the size of the image on the film or sensor is the same size as the actual subject. Images where the sensor image is larger than 1:1 is normally considered macro photography.

This is a film format using the 35mm movie film. Because of reduced cost for both media and equipment along with smaller sized equipment, it soon became the most popular choice in film photography. The full frame image is 24 x 36 mm.

With image stabilization systems, the top of the line cameras has a 5-axis movement correction. • Axis 1 - Up and down with the camera moving in a vertical manner. • Axis 2 - Side to side with the camera moving in a horizontal manner. • Axis 3 - Camera vertical rotation. • Axis 4 is Yaw, which is a rotation in a circular motion from side to side. • Axis 5 is Pitch, which is a rotational or circular movement an example is rotating so the horizon is not level.

Similar to the 500 rule; but this is used for astronomical photography, giving the longest shutter opening time without creating star trails. In this case it is vital to have the camera on a tripod. To do this divide 600 by the focal length of the lens to get the shutter speed i.e. with a 60 mm lens, 600/60 the shutter can be opened for up to 10 second.

A camera control where the photographer selects the aperture and the camera's internal meter selects the corresponding shutter speed. This is usually for control of depth-of-field.

Camera Settings

A distortion of image quality or color rendition in a photographic image caused by optical limitations of the lens used for image capture, usually not having all the data from a single point focus in the same plane. Aberrations commonly show up in the form of halation around high-contrast portions of the image, or "smearing" of color toward the edges of the frame. Aspheric lens surfaces and advanced lens coatings are often used in more expensive or complex lenses as a means of reducing aberrations.

The preferred color space for professional print-based photography with a gamut that closely approximates the CMYK printer's gamut.

Softness that appears when the aperture is stopped down too far. Light passing through a large opening comes out in one coherent bunch, like water from a hose at low pressure; squeeze the opening down and the light begins to scatter at the edges, just as the hose starts to spray. Past a certain aperture that scattering blurs fine detail across the whole frame no matter how good the lens is. The smaller the sensor, the sooner it arrives.

Optics

A sensor format smaller than full frame but larger than Micro Four Thirds, typical of Canon and Nikon starter systems. A capable general-purpose amateur format, but rarely the one professionals choose for the highest quality work, and rarely a system you can grow upward inside.

Sensor Formats

Faint dark stripes, usually at the edges of objects, that appear when pixel data falls out of step between camera and computer. Of the three kinds of noise it is normally the least serious, and it can often be corrected in editing software.

Sensors & Noise

The mosaic of microscopic color filters laid over the sensor. The light-sensitive diodes are themselves colorblind, so each is given a red, green, or blue filter: one row alternates blue and green, the next green and red, giving the array twice as many green pixels as red or blue. The camera reconstructs full color from the mosaic by demosaicing.

Sensors & Noise

A glow or halo that spreads around a small bright subject photographed against darkness, such as a lit flag at night. It is a limit of the sensor, not of technique: very bright light overfills small pixels and spills into their neighbors. Larger sensors with larger pixels contain it better, and the demosaicing process helps limit the spread.

Sensors & Noise

A specialist astronomy camera whose sensor is refrigerated far below freezing while it works. The cooling silences the sensor's own noise, leaving it many times more sensitive than an ordinary array: blacks come out truly black and faint stars stay clean. Only a few companies make them, and they are very expensive.

Equipment

Saved banks of camera settings that can be recalled with a dial position or button. Set one up for each situation you shoot often, and switching to it applies every stored setting at once. This avoids the classic failure: settings dialed in for one situation, then one of them forgotten when the situation changes.

Camera Settings

The reconstruction of full color from the Bayer mosaic. Each pixel behind its single filter is a pixel well that knows one color's brightness and nothing else. The processor walks the entire sensor and, for every pixel, reads it together with its eight neighbors, weighs the reds, greens, and blues among them, and assigns the center pixel its final color. On a 50-megapixel sensor that happens fifty million times, faster than you can think about it.

Sensors & Noise

Lightening (dodging) or darkening (burning) chosen areas of a picture, a technique as old as the darkroom, where it was done by holding light back from the paper or giving it extra. Digital editors do the same with brushes and masks. Used well it is invisible: it guides the eye and connects the parts of a composition rather than announcing itself.

Post-Processing

A motorized mount, aligned with the Earth's axis, that turns the camera with the sky so stars stay sharp points during long exposures instead of streaking into trails. Camera-sized versions are sold as star trackers and typically cost several hundred dollars.

Equipment

The sensor format matching a 35 mm film frame. For low light and the night sky it is the practical minimum: bigger pixels keep the signal above the noise. Notice that the finest low-light bodies carry only 20 to 25 megapixels rather than 60 or more. Fewer, larger pixels are the point, not a compromise.

Sensor Formats

Specks of purple or white in the dark parts of an image, caused by pixels that switch on slightly early. No two diodes leave the factory identical: each has a faintly different threshold before it responds, and in shadows, where the true signal is tiny, the early switchers stand out. The camera compensates by reading the sensor in total darkness as the shutter is pressed, building a mask of the offenders, and subtracting that mask from the picture.

Sensors & Noise

The circle of usable image a lens projects behind it. Lenses for small cameras project a circle barely larger than the sensor, which keeps them affordable. View camera lenses project a far larger circle, leaving room to move the lens up, down, and sideways within it. Those movements are what let a view camera correct perspective and bend depth of field in ways smaller systems cannot.

Optics

Sensor formats larger than full frame, favored where image quality outweighs everything else. The large sensor means large pixels, wide tonal range, and prints that hold together at any size.

Sensor Formats

The smallest of the common interchangeable-lens formats. Its featherweight sensor moves fast and far in its stabilizer, depth of field is immense, and long lenses stay small, which makes the format a favorite for birds and wildlife. Its limits: diffraction arrives early when stopping down, and serious low-light or night work wants a bigger sensor.

Sensor Formats

Shimmering false patterns and colors that appear when a fine, regular pattern in the subject interferes with the regular grid of the sensor. It is a form of random noise: it depends on the subject, so the camera cannot map it out in advance.

Sensors & Noise

Photography after sundown, which is less about darkness than about balance. The best night shots are usually made before total darkness, while the sky still carries light to weigh against the lamps and windows. Once the sky goes fully black, lights burn out against nothing and the picture loses its shape.

Field Technique

A pop-up fabric hide, sold in hunting departments, with ports to shoot through. Set it up and be still: birds and animals accept it as part of the landscape and come remarkably close.

Equipment

A high-resolution mode that uses the stabilizer's suspension deliberately: between frames the sensor is moved by half a pixel or a whole pixel, and the shots are combined into one image with truer color and more detail than any single frame. The movements are microscopic, and larger sensors do it best.

Sensors & Noise

A burst mode that reaches back in time. With the shutter half-pressed the camera continuously keeps the newest frames in its buffer, thirty to seventy of them on a stacked sensor. At the full press it saves those frames plus a set afterward, so action that finished before you could react is already recorded. Lift your finger and half-press again, and the buffer resets.

Field Technique

Noise that depends on the subject as much as on the sensor. It arises where fine detail falls awkwardly across pixel boundaries and through the demosaicing arithmetic: a line half in one pixel and half in the next. Because it changes with every scene, the camera cannot mask it out in advance the way it removes hot pixels. Moiré is its most dramatic form.

Sensors & Noise

The rule of thumb for handholding: keep the shutter speed at least as fast as one over the focal length. A 125 mm lens wants 1/125th of a second or faster; a 500 mm lens wants 1/500th. It is only an average. Steady hands cheat it by two or three stops, unsteady ones cannot reach it, and in-body stabilization rewrites it altogether.

Field Technique

Divide the frame into thirds both ways and place what matters on the lines and their crossings rather than in the center. Which third you choose is a statement about what the picture is about: the element given the larger share becomes the subject.

Composition

Classic sharpening adds no detail. It hunts for edges and pushes the bright side brighter and the dark side darker, and the eye reads the extra contrast as sharpness. Pushed hard, it turns speckled and artificial. Newer AI sharpeners work differently: they recognize what the subject is and rebuild its edges from knowledge of similar subjects, which goes much further before it breaks.

Post-Processing

The measure that decides how clean an image looks, and the reason all noise lives in the shadows. A brightly lit pixel might put out five volts; a shadowed one, a hundredth of a volt. The same tiny error that disappears against five volts is ten times the entire signal of the dark pixel. Bigger pixels gather more light and keep the signal far above the error, which is why low-light cameras favor fewer, larger pixels.

Sensors & Noise

A sensor with its buffer memory built directly onto the back of the chip, so frames move off the sensor with almost no delay. That speed is what makes silent high-speed bursts and pre-capture buffers of thirty to seventy frames possible.

Sensors & Noise

Enlarging an image beyond its native pixel count. Traditional resampling, as in Photoshop, holds together for roughly a twenty to thirty percent enlargement before problems creep in. AI-driven tools go much further, multiplying the pixel count several times by recognizing subjects and redrawing them from a learned database.

Post-Processing

A body style, or add-on grip, carrying a second shutter button and duplicate control dials on the bottom corner, plus a much larger battery. Turn the camera vertical and the same controls sit under the same fingers, thumb on the same command dial: no elbows in the air, no groping for the shutter, on shoots that swing between horizontal and vertical.

Equipment

Fujifilm's alternative to the Bayer array. It keeps the green majority but lays the filters out in a larger, less regular pattern, and the irregularity is the point: with no strict grid for the subject's own patterns to drum against, fine weaves and textures cause far less moiré.

Sensors & Noise