What are Shooting modes?
If you have read the post on Exposure (link to Improve your digital photography – Exposure) you will be aware of the 3 factors affecting exposure – Aperture, Shutter speed, and ISO. Modern DSLR cameras come with a range of shooting modes, which range from full auto, where the camera decides on all of the variables used to correctly expose the image, to Manual mode, where you as the photographer make all of the creative decisions regarding the image exposure.
You will also find a couple of “semi automatic” camera modes, these are Aperture priority (usually A or Av on the cameras mode settings dial), and Shutter priority (S or Tv (time value) on camera mode dial). What these shooting modes do, is to allow you to control the aperture size in the aperture priority mode, or the shutter speed in shutter priority mode.The other variables are controlled, and set automatically by your camera.
Aperture priority mode.
In aperture priority shooting mode, you set the aperture size, which will also help to determine your shots depth of field. The camera will set the shutter speed and ISO (if you have ISO set to auto). By setting a specific ISO to take into account the prevailing light conditions, or for maximum image quality, the camera will then only be setting the shutter speed.
Let us say that you choose to set the ISO to 100 for better image quality, you then compose your shot, and the using the main dial (by the shutter button usually), you can easily change the aperture setting. If your camera has a DOF preview button, you can use it to assess what changing the aperture does to DOF.
As you change the aperture size, your camera will set a shutter speed using the light meter reading, based on the information of the ISO and aperture that you have set, producing a correctly exposed image. You may choose to use aperture priority mode for images where you wish to control the depth of field of the final image.
Always be aware of what shutter speed is selected by your camera as it may drop too low to avoid some camera shake. Increasing the ISO will allow a faster shutter speed if this happens.
Shutter priority mode.
In shutter priority shooting mode, you are setting the shutter speed, and the camera sets the aperture, and ISO (only if you have ISO set to auto). This shooting mode would be useful if you needed to either freeze motion, for example taking shots of your child running around playing, or sports action, or wildlife where your subject can move.
The faster the shutter speed, the more the movement is frozen. You might also be trying to impart some motion blur into an image, to give a sense of movement, so a slower shutter speed would be needed. The process is as for Av mode, only you are trying to use a more appropriate shutter speed for the effect you are trying to capture.
Always be aware of what aperture is selected by your camera. The shutter speed you select may mean that the camera has the aperture wide open, but this may not give enough light for the shot. Once again, increasing the ISO will allow the faster shutter speed if this happens.
By choosing the manual shooting mode, you are taking full control of all aspects of the shot. The type of look you are going for in your image will determine how you set up for the shot. Trying for some motion blur, set the shutter speed you are likely to need, then the aperture should be set to accommodate this. Your in camera exposure will show you when the exposure is correct.
Use the same principle for shooting images where DOF is important, only you would set the aperture you needed for the photograph, then adjust the shutter speed accordingly. If you are unsure if your exposure is exact, you can always use exposure bracketing, then select the image you feel is correctly exposed.
To find out how to select the various shooting modes in your camera, refer to your camera’s manual. You will also be able to discover how to adjust Aperture and Shutter speed on your camera here as well.
What all of this means is that you are taking more control over how your final image will look.