All You Need to About Digital Photography

The exposure time, also known as shutter speed, along with the aperture and ISO value, is one of the three fundamental parameters that affect the exposure of a photo (PDF only available in German). As the term already suggests, the exposure time affects how long the shutter of the camera remains open after pressing the shutter release to allow light to hit the sensor.

Short exposure times are best suited for taking sharp photos of moving motifs, such as in sports photography. If a movement is captured with a very short exposure time, the term “freezing movement” is used.

A dynamic photo is a picture that intentionally employs motion blur for stylistic effect. A simple example of this is a flowing waterfall being photographed with a long exposure time to make it appear soft and misty.

Factors such as colour rendering, contrast, focus, and detail reproduction all contribute to the image quality of a photo.

These factors are heavily influenced by the image quality of the lens, the camera sensor, and the effectiveness of the image processing. Thus, good image quality results from the optimal combination of these components and is strongly influenced by the quality of your camera.

An image stabiliser reduces blurriness during freehand photography. It’s important to keep in mind, however, that this only compensates for movements made by the photographer and not for movements of the motif.

Here, a distinction is made between optical, mechanical, and digital stabilisers. Optical image stabilisers contain movable mounted lenses. Sensor-shift image stabilisation, on the other hand, is mechanical and occurs through the electromagnetic movement of the sensor. The mobility of either the lenses or sensor can compensate small movements made by the photographer. This also enables the photographer to use longer exposure times.

Digital image stabilisation is carried out through adjustments of the following exposure parameters: aperture, ISO, and exposure time. Here, the ISO value is usually raised considerably in order to keep the exposure time as short as possible.

The opening of the aperture regulates the amount of light that is allowed through to the camera’s sensor through the lens. When talking about the aperture opening, the term f-number (or f-stop) is usually used, which is usually displayed as a fraction. With a large f-number, such as f/4, the aperture is opened wide. With a smaller f-number, such as f/22, it’s barely opened.

It’s not uncommon to see an f-number displayed as just a whole number instead of a fraction. Be careful not to get confused here: when displayed as a whole number, a low f-number (4) means the aperture is opened wide and a high f-number (22) means the aperture is barely opened.

The focal length of a lens is determined by the distance between the lens and imaging plane. The longer the focal length is with a sensor of the same size, the motif is more enlarged and the image angle is more reduced.

A “normal” camera lens has a focal length of 50 mm, since this is approximately equivalent to the angle of view of the human eye. Lenses with a focal length shorter than 50 mm are wide-angle and lenses with a focal length shorter than 20 mm are super wide-angle. Lenses with a focal length longer than 50 mm are categorised as telephoto lenses.

In contrast to the human eye, a camera sensor has a limited dynamic range, which is why it can adapt to various ambient lighting conditions only to a certain extent.

Quick changes between bright and dark environments are particularly challenging for the sensor to handle.

The dynamic range describes the range between the darkest and brightest area of a motif and spans over a maximum of 23 f-stops. The human eye spans across approximately 20 f-stops while a modern high-quality camera only covers 9-12 of these f-stops.

Should the dynamic range of a camera be exceeded when photographing, the image information found outside the dynamic range will be lost. This leads to over- or underexposure. When this occurs, the term “burned” is often used.

Colour depth describes how many bits are utilised to depict each colour component of an individual pixel. If an image is saved with 8 bits, 256 different colours can be depicted. The term “bit” is a portmanteau from the field of informatics and is a unit of measure for digital data volumes. A 24-bit image can depict 16.7 million different colours. This very realistic colour depiction is also called “true colour.” Colour gradients appear to be especially more stepped the less colour depth an image has.

The golden ratio describes a particular division ratio of a section of the photographed motif. The proportions of the golden ratio appear especially aesthetic since it can be found in both nature as well as humans.

Here, a section is divided into two parts called “major” and “minor.” The major portion is 61.8% of the whole, and is thus the larger portion.

In everyday use, it’s not easy to perfectly divide a section according to the golden ratio, which is why a simplified ratio of 3:5 is often used.

The acronym HDR stands for high dynamic range (see dynamic range). An HDR image produces a photo that is closer to the actual perception of the human eye than normal photographs.

There are various methods of producing such an image. There are special cameras available that have a higher dynamic range than conventional cameras. Since these cameras are very expensive, however, they are not used by hobby photographers.

Many modern cameras these days come with an HDR function, which generates an HDR image directly from several individual images. The image is generated from an exposure bracketing of at least three differently exposed images. Every section of the motif must be correctly exposed on at least one of these images in order to generate an HDR image.

The ISO value indicates the photosensitivity of a recording medium. In digital photography, the ISO value regulates the light sensitivity of the sensor and can be changed from photo to photo.

ISO values between 100 and 200 are considered standard. When the ISO value is doubled and thus the light sensitivity of the sensor increased, the exposure time is also conversely halved. When increasing the light sensitivity of the sensor, this not only makes the sensor more receptive to light, but also to interference – so-called “image noise” can appear.

The JPEG file format is often used as the image file format for digital cameras. JPEG is a compression format that compresses the size of the file, but also somewhat degrades the image detail and colour fidelity.

Images with a .jpg file extension that are opened and saved multiple times can experience further degradations since the compression is intensified and image information is lost. There is no loss of information with the RAW format.

The lens speed is one of the three fundamental qualities of a lens and describes the maximum aperture ratio of a lens.

The area where a motif is in focus is called the depth of field. Depending on what is being photographed, much or little depth of field is required.

When photographing landscapes or architecture, usually the whole motif should be sharply depicted. In order to achieve this area-wide sharpness, the aperture should be closed as much as possible in order to give the image a better depth of field.

With other motifs such as portraits or close-ups in macrophotography, a wide-open aperture is used in order to keep the depth of field to a minimum. Limiting the area of sharpness makes the background appear blurry and makes the photographed motif appear that much more sharp in the foreground.

A camera’s zoom enables you to enlarge or minimise a motif without having to change your own position. Here, a distinction is made between a digital zoom and an optical zoom.

A digital zoom only enlarges the image section, which can lead to lower image quality. Smartphones and compact cameras often only come equipped with a digital zoom.

In contrast, an optical zoom alters the actual focal length. When the lens of a zoom lens is placed further away from the sensor, the focal length becomes longer, which minimises the image section and zooms in on the motif. If a motif should be minimised, the converse occurs.