Taking your camera out of the auto mode is a big leap, but one that is necessary if you are going to fully realize what your camera can do. It’s just like the first time you learned how to drive and took over from your driving instructor. A lot of DSLR owners never manage to use the manual modes on their DSLR cameras. They end up never fully realizing the potential that their camera has got to offer. It’s like buying a Porsche and only driving it 5 miles to work.
Your DSLR camera is designed to give you full control over exposure, among other things. It opens up a plethora of creative options for you. To understand how to make effective use of that feature, you need to have a clear understanding of what exposure is first. This article will help you get a good grasp over the fundamentals and at let you dip your toes in manual mode waters.
The auto mode of your camera is guided by what the camera thinks is the average exposure for an average scene. It is not a rule, but rather a guide which may or may not give you the right exposure for every scene. Sounds kind of confusing isn’t it? Let me explain it in a more easier terms. Your DSLR comes with a built-in metering system. It assesses the light reflected off a scene and determines the right exposure values (shutter speed and aperture), for a given ISO number which will produce a well exposed image. The problem lies in that the camera is designed to look at everything as if it’s 18% grey. On the luminosity scale 18% grey has a middle reflectance. It absorbs about the same amount of light that it reflects back. The biggest disadvantage of that is that the camera tend to overexpose when it looks at a dark scene and under-expose when it sees something too bright. This comes from the same old concept that we read in the chapter on Light in school Physics. A white surface reflects all of the light that falls on it. A black surface on the other hand absorbs everything. Thus for a white scene the camera will reduce the exposure, cutting down light and in effect making it grey. For a predominantly black scene the camera will increase the exposure and in the process, also make it grey.
If, for example, you wish to shoot a snow scene, the auto mode is never going to give you the exposure that you want. It’s always going to make it look grey. To make the scene look white you will need to do a forced overexposure. There are two ways of achieving that and both requires that you get out of the auto mode. You can also check out our How to See Like the Camera to Properly Use Exposure Compensation article, which is all about shooting the snow scenes.
The first method uses a feature known as exposure compensation. The second method entails using the manual shooting mode. Exposure compensation allows you to set a positive or negative ‘bias’ over what the camera thinks is the right exposure value, if you want to learn more about it, check out our Exposure Compensation article. But in order to use this feature you need to get into one of the creative manual modes. The creative manual modes include the programmed auto, aperture priority and the shutter priority modes. These modes allow you to control one of the aspects of exposure value while the camera controls the other aspect (except in the case of programmed auto mode where you are able to adjust different combinations of the exposure values and not just one single exposure value).
Let’s say you are in aperture priority mode. The aperture priority mode leaves the choice of aperture to you. For each aperture that you choose, the camera will select the appropriate shutter speed. You can find out more about in in our Using Aperture Priority Mode article. Similarly, in the shutter priority mode the camera will automatically select the appropriate aperture for the shutter speed that you choose. Check out our Using Shutter – Priority Mode article to learn more. But you are still able to override what the camera thinks is the right aperture or shutter speed by using exposure compensation.
In the manual mode the camera gives you the choice to control both the aperture and the shutter values by rotating the main and sub-command dials. Manual mode is the best in terms of complete control over exposure. You can choose to over or under expose a scene, as per the requirement of the image, without the camera forcing you to select something that it feels is right. Also, you no longer need to use exposure compensation because you can change the exposure values at will. Having said that, exposure compensation can still be used in manual mode.