In previous weeks we have isolated three aspects of our camera which govern exposure. Shutter Speed, Aperture, and ISO. These three parameters form what is often referred to as the Exposure triangle. As we move into using full manual this week, let’s review precisely how each of these affects our images.
Remember this dial?
When shooting in P, Av, or Tv, we changed this manually, while setting shutter speed, aperture, and/or ISO and letting our cameras figure out the others automatically. We called this exposure compensation. When we wanted a darker image, we’d dial it down towards the negative left sight and conversely for brighter shots. With manual, this dial becomes an indicator of the amount of light that’s reaching our sensor. In general we want the cursor to rest at 0 (though in practice I tend to prefer -1/3 or -2/3). Every time we focus the camera by half pressing the shutter, it will give us a reading here. How can we use the exposure triangle to get to the hallowed zero mark?
| Brighter | Darker | Tradeoff | |
| ISO | Higher (12800) | Lower (100) | Grainy image |
| Aperture | Larger (F4.0) | Smaller (F29) | Depth of field |
| Shutter Speed | Slower (30”) | Faster (1/4000) | Motion blur. Hand shake |
As you can see from the table above, you can use any of the three parameters to brighten or darken your image appropriately. Remember, however, that bumping up your ISO will result in a very grainy image with a lot of visual noise. A larger aperture will have a shallow depth of field (which you might want!). A slower shutter speed will be unable to freeze time. Keep these in mind as you decide which aspect to alter. Is your subject still? You may then want to use a slower shutter speed and a timer so as to enable lower f-stops and ISOs.
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