akemi photography blog
♥ What is Exposure?
Exposure (in photography) is the amount of light allowed to fall onto the film or image sensor when taking a photograph.
♥ How does my camera measure exposure? Why not always use the camera’s automatic exposure?
On a digital camera the exposure system works on the assumption that the area of a scene is being metered as a mid-tone (18% grey). That is, combine the light, mid and dark tones of a scene and the result is an 18% grey. While this system works well in the majority of situations, it can led to incorrect exposures when a scene is considerably lighter or darker than 18% grey.
♥ What is the exposure triangle?
There are three settings which combine to give you the exposure, these are Aperture, Shutter Speed and ISO. Each can be changed individually allowing you to set them to what you think will give you the perfect exposure, or you can let the camera set them for you to what it thinks is the perfect exposure for the conditions it detects.
♥ What is underexposure?
An underexposed image is when too little light was received by the camera sensor as a result of insufficient exposure time for the available light source/s. Resultantly the image is too dark, has blocked shadows (no detail available in the shadow or black areas of the image) and the colours appear muddy.
♥ What is is overexposure?
An overexposed image is (unsurprisingly) the opposite of an underexposed image. An overexposed image is when too much light was received by the camera sensor as a result of too much exposure time for the available light sources. Resultantly the image is too bright/light, has blown highlights (no detail available in highlights or white areas of the image) and colours can appear washed out.
♥ What is exposuring to the right?
Exposing to the Right applies if you are shooting in raw and is one approach to help maximise image quality. With the Exposing to the Right technique you push the exposure settings (hence the term ‘exposuring to the right’) as close to overexposure as possible without actually clipping the highlights. The resulting histogram has the majority of the pixels grouped to the right of the mid point. As sensors count light photons in a linear fashion, the majority of the tonal values are recorded in the right side of the histogram. An underexposured image could potentially result in the loss of a large percentage of data that can be captured and increased noise.
♥ What is exposure compensation?
Exposure compensation is the simplest way to override the camera’s metered exposure. Exposure compensation allows you to to dial in a set exposure increment for increasing or decreasing the the exposure. For example, where a scene is significantly lighter than mid grey and the camera metering would typically result in an underexposed image, you need to select the positive (increase) exposure compensation. The exact amount of compensation to be applied to an image is dependant on the subject and lighting conditions.
♥ What is exposure bracketing?
Exposure bracketing is when you shoot a sequence of the same subject or scene, all using different exposure settings. This can be used as precaution to ensure that you will get the correct exposure and is also used for creating High Dynamic Range (HDR) images. Most SLR cameras are now designed with an Auto Bracketing facility.
Further Reading & Resources
Posted in: for the familiographer