SLR cameras have at least 5 basic modes, which can usually be controlled using a wheel on the top of the camera. With this shutter speed dial you can switch between different shooting modes. The five most important options for photography are AUTO, P, A (or Av), S (or Tv), and M. Automatic mode is marked with “AUTO” or a green box with an “A”. P stands for Program Mode, A (Av) for Aperture Priority, S (Tv) for Shutter Priority, M for Manual Mode. In addition, most cameras still have various scenery modes and possibly also a video mode.
Automatic program mode is not the same as automatic mode (fully automatic), since important shooting parameters can be varied depending on the camera model. Only the aperture and shutter speed are controlled by the camera and automatically adjusted by the camera’s metering mode. Typically, when ambient light becomes poorer, the aperture is opened further and the exposure time is increased at the same time.
In contrast to auto mode, P mode allows for manual control of the flash and other settings such as the ISO value or exposure corrections. In comparison to the aperture or shutter priority, the image is also properly exposed when the ambient conditions change quickly, making manual adjustment difficult.
Why take photos using program mode and not just auto mode?
For many DSLR users, P-Mode is the standard program for snapshots and works well for a variety of shooting situations. Even though it is very convenient to use, since both aperture and exposure time are automatically adjusted, the photographer does not lose complete control over the settings, as is the case in automatic mode. It is therefore a kind of “basic auto mode”.
Most importantly, in program mode, you can manually decide whether or not to use the flash. Especially indoors, flash photography often creates an artificial atmosphere – the decision when to use it should be made by the photographer depending on the situation. To use the flash, it must first be opened manually.
The ISO setting can be adjusted by the photographer depending on the lighting situation. You can try out at which ISO values the optimum exposure is achieved. Depending on the camera model, high ISO values in particular can lead to considerable image noise, which should be taken into account when adjusting the settings.
The white balance can also be adjusted as desired.
Furthermore, P mode offers the option of exposure correction. This can become necessary, as the exposure measurement is based on average subjects in which bright and dark areas are relatively evenly distributed. If the subject is generally very bright or very dark, it deviates too much from these average values and incorrect exposures occur. These can be corrected by means of an exposure correction.
In addition, automatic exposure series can be captured in program mode, as required for HDR images. Only the shutter speeds are changed and not the aperture, so that the photos can be merged and superimposed later.
Program P recognises the focal length used by interchangeable lenses and tries to keep the shutter speed so short using the aperture and (with ISO automatic) the ISO settings that handheld shots are possible without blurring up to minimum lighting.
The image quality should be checked directly when using P mode and the corresponding parameters should be adjusted if necessary.
Drawbacks of program mode
Program mode responds to two basic requirements: The image should be correctly exposed and it should be sharp. In combination, the aperture and shutter speed must always match.
However, there is more than one combination that leads to the correct exposure. If, for example, you open the aperture a little (assuming a correct combination) and reduce the exposure time accordingly, you get another correct combination regarding the exposure with a different depth of field. The depth of field of a photo is often used as a creative tool, for example. By default, program mode cannot be set accordingly.
Program shift functionality
P mode prefers short shutter speeds to high f-stops. The combination of aperture and shutter speed defines depth of field and motion blur. If the aperture is too small, for example, but the subject requires more blur in the background, program shift (or flexible program) can be used with many camera models. While preserving the exposure value, the time/aperture combination determined by the program mode is overwritten manually. Depending on the camera, the program can be shifted using a dial on the shutter release button or using the arrow keys on the back of the camera.
The aperture and shutter speed are not shifted individually, but simultaneously. This guarantees that the exposure itself remains unchanged in accordance with the current lighting situation. Program mode takes changed lighting conditions into account in its parallel shift, but the direction of the shift is retained. Depending on the camera and settings, this program shift is only valid for the current shot or for a defined time.
Other modes / scene modes
The selection of the time/aperture combination always considers the interplay between the correct exposure time and the optimal aperture setting for depth of field. This is why most modern cameras offer more than one program to cover different situations. The settings follow a kind of “patent recipe” for the corresponding subject.
The portrait program selects an aperture that is as open as possible for a shallow depth of field. Landscape and panorama programs as well as close-up programs select an aperture that is as closed as possible for a large depth of field. The sports program uses the shortest exposure time to reduce motion blur. The night program uses a long shutter speed for long time exposures.
Depending on how much the photographer uses the manual settings of their DSLR in program mode, essential parameters of the photo can be influenced. It is always ensured that the combination of aperture and exposure time allows for a correct exposure. With program shift, almost the same settings can be made for individual images or exposure series as the semi-automatic modes Av (A) and Tv (S) would allow. If other scene modes are used or no custom settings are made in P mode, the mode comes close to AUTO mode.