So what does that all mean? Good question. I am a visual learner, which means that I learn best when I can see the relationship between objects. With this in mind, I put together this table, which shows 'one stop increments' in terms of shutter speed, aperture, ISO, and exposure compensation (EV). Let's look at each individually.
Since ISO is one of the first things I determine when I am shooting, let's look at it first. The lower the ISO, the less grain you will have in your photo. At higher ISO settings, the photo will show more grain. Granted, I am no expert in determining which ISO setting to use. That being said, here's what I usually do: Most of what I shoot is between 200 and 400 ISO. If I am shooting in bright sunlight or under studio lights, I may use ISO 100 or 200. In lower light settings, I'll go to a higher ISO.
Next, I think about depth of field, which is determined by the aperture setting. For landscapes with a deeper depth of field, I might use an aperture of f8 or higher. When shooting portraits or macro photos, I might select a larger aperture setting of f1.4, f2.8, or f4. An excellent tool to determine the depth of field may be found at http://www.dofmaster.com/.
Next is shutter speed. If I am using my Sekonic L758-DR light meter, selecting the shutter speed is easy. However, this project is all about me being able to select an ISO, aperture, and shutter speed without having to use the meter.
So let’s talk about a couple of situations and how I use the table above to guide me in determining settings.
Recently I was shooting in hotel banquet hall (which always seem to have terrible lighting). Because the room lighting was somewhat dim and I was unable to use flash, I set the ISO to 1600. Let’s think about what that means in relation to shutter speed and aperture: An ISO of 1600 means that we can use a faster shutter speed and a smaller aperture. Since I was shooting from about 35 feet away, I wanted to make sure my aperture setting provided enough depth of field to provide sharp focus on all my subjects. Using www.dofmaster.com, I could see that using an aperture of F8 with a focal length of 100 mm gives me a depth of field of about 12.2 feet (5 feet in front of the subject and 7 feet behind), which is plenty to assure that the five people on stage would be in focus. But what if I had used my faster Nikon 80-200 f2.8 lens? At an aperture of 2.8, the total depth of field would have only been about 4 feet (2 in front and 2 behind). This means that some of my subjects would have been in focus and others would have been out of focus. If I had the DOF Master application on my iPhone, I could have figured the depth of field on the spot. However, I erred a little on the side of making sure I had adequate depth of field so that I could assure sharp focus across all the subjects on stage.
Here’s another scenario. I am shooting a portrait of one person under studio lights. Because the lighting is excellent and controlled, I set my ISO for 100. I want to have a shallow depth of field so that the subject stands out from the background so I set the aperture to a large setting, perhaps f2.8. In this situation, I could use a light meter (which was impractical in the last scenario). In the absence of a light meter, I would use my camera meter to find a starting point for shutter speed.
So what about the graphic? This just helps me to see that if I need more light I have a variety of options: I can decrease the shutter speed (not always practical), select a larger aperture (which impacts the depth of field), increase the sensitivity of the sensor by increasing the ISO setting (which may cause more grain), or I could add one stop of exposure compensation by adding 1 EV.
Clear as mud? Almost.
Remember that I am the student and I’d be interested in hearing from anyone who can share how they do things. Let me hear from you. Until then,
All the best…
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