Photographing indoors often poses two problems: low light and high contrast between the interior and exterior. This is often the case in naturally dark places such as concert halls, sports halls, museums, churches; or in times when the light is naturally low: early in the morning or at dusk.
In cases where the photographer cannot rely on good natural light and cannot control the light himself, he must adapt the settings of his camera in order to capture the light as much as possible, even if it is very weak. Several parameters must be considered.
The settings for photographing in low light
To achieve a well exposed image despite the little ambient light, it is necessary to adjust the camera taking into account 3 parameters that determine the quality of exposure of a photo: the aperture, shutter speed and ISO sensitivity.
To photograph in low light conditions, it is better to use a bright lens that can capture a lot of light with a very large aperture of the lens diaphragm. Note: the smaller the number, the larger the opening! Increasing the aperture will directly reduce the depth of field (the area of sharpness on the image) and therefore risk creating blur (bokeh) in the background.
The second parameter is the shutter speed, or exposure time. The slower the shutter speed, the more light the camera sensor is exposed to and the brighter the photo. It is therefore possible to increase the exposure time to properly expose the photo.
Finally, the photographer can also compensate for low light by setting the ISO sensitivity high (the ISO sensitivity measures the sensitivity to light of digital sensors, it is essential to determine a correct exposure). The latest cameras offer good image quality, without excessive noise, up to ISO 6,400. Increasing the ISO sensitivity of the camera makes the sensor more sensitive to light. But be careful, it can also deteriorate the quality of the image.
A solution to photograph in low light can be to opt for a low ISO sensitivity, to expose at a slow speed if you want to diaphragm the lens to an aperture giving a good depth of field (for example f/8 or f/11). A tripod is then necessary to avoid any risk of movement; it also allows to refine the framing. However, cameras, especially hybrids, and lenses that have a stabilization system, make it possible to work freehand. The photographer should test to see how far his or her equipment can go at slow speeds. Some camera-lens combinations keep the image sharp up to 1 second of exposure thanks to stabilization.
Another solution is to bring light with a flash. To solve a problem of too little light, the photographer can also create the missing light with one or more flashes, to better illuminate his shot and obtain the desired result.
The case of architectural photography
In architectural photography, the contrast is often high between the areas overlooking the outside (window, door, bay window, etc.) and the interior parts. If the exposure is calculated to keep details in the brightest areas of the image, the shadows can suffer and lose their substance.
Lightening low-detail shadows in post-production often results in noise and a loss of color differentiation. The problem is reversed if you expose for shadows. The highlights can reach an overexposure that cannot be recovered in postproduction: no detail will be recoverable.
The solution is then to make two images, one exposed for shadows, the other for highlights. The two images will be merged in post-production, in order to restore what the eye is capable of recording in
high contrast situations.