What is an Exposure Compensation?
Exposure Compensation is one of the great features of today’s camera that allows you to adjust the exposure measured by its light meter. The range of adjustment depends upon camera. In case of Nikon D90, this range goes from -5 EV to +5 EV in increments of 1/3 or 1/2 EV. EV stands for Exposure Value.
This means that you can adjust the exposure measured by the light meter by telling the camera to allow more light in (positive exposure compensation, +EV) or to allow less light in (negative exposure compensation, -EV). Depending upon how your digital camera deals with exposure compensation and the shooting mode used, it may adjust the aperture while maintaining the shutter speed constant; it may adjust the shutter speed while maintaining the aperture constant; or, it may adjust both the aperture and shutter speed.
Here I have included couple of photographs to demonstrate positive exposure compensation.
At Normal condition (Without applying Exposure)
Applying Positive Exposure Value (+0.7 EV)
What is an Exposure Bracketing?
Exposure bracketing is a technique to make sure that pictures are properly exposed under challenging lighting condition. Most of the times camera’s sensor will automatically set the exposure setting by selecting an aperture and/or shutter speed combination to give best result. But it doesn’t work all the time. Sometime you want to set exposure manually.
Exposure bracketing technique allow you to take two more pictures: one slightly under-exposed (e.g. -1/3 EV), and the second one slightly over-exposed (e.g. +1/3EV). This range of adjustment vary with Camera’s light meter. I believe it goes from -5 EV to +5 EV with 1/3, 1/2, 2/3, 1 or 2 EV range in case of Nikon D90.
When should we use Exposure Bracketing?
Whenever there is complex situation of lighting, you should use this feature to get proper result. Some photographers don’t like to use this feature at all. They prefer to look at LCD and take another shot if they don’t like current one.
But the main reason we do this is to adjust proper lighting condition over our main subject. Sometime camera’s sensor get confused by light (too much or too little) to main subject and hence subject may be over-exposed or under-exposed. Taking three shots with variation of exposure is good idea in this case. That is why we use bracketing.
As an example, you can see my above picture that I took under normal condition. But it came out dark. Then I applied positive exposure compensation value and got good result.
Another example would be, lets say you are shooting comparatively dark subject in snowy area. Your camera meter will adjust exposure with the surrounding amount of light coming from snow. In this case camera senses more light and adjust aperture size (small aperture number) and shutter speed (faster shutter speed). When you take picture in this case, your main subject will be under-exposed and come out dark. In this case you want to set exposure value to +EV to get proper expose to main subject and surrounding my be over-exposed little bit.
Today’s almost every DSLR camera allows you to shoot with different exposure value using automatic bracketing feature. If you are using Nikon D90, you can check my post on Automatic Exposure Bracketing (AEB) to setup camera controls for Nikon D90.