How to Measure the Contrast Ratio on a Canon to 4:1

Measuring contrast ratios means understanding how much light hits in various parts of a photograph. Higher contrast ratios have a lot of light on one side of the subject and less on the other. Lower contrast ratios are more evenly lit. A 4:1 ratio means that two times more light fall on one side of the subject than on the other. Traditionally, photographers used light meters to measure the amount of light in different areas of an image. Digital cameras in widespread use means that traditions such as light meters are somewhat less common. However, by understanding the principles of light ratios, you can still get good results simply by doubling the amount of light in a particular spot of the image.

Instructions

1

Assemble your lights. If you are using professional-grade lights, check their wattages. You should have lights of 100 watts, 250 watts, 500 watts or more.

2

Eliminate extra light sources in the room around your subject. Turn off overhead lights and block out window light completely.

3

Put the key light on the subject. The key light is the strongest, primary light, and depending on your film speed you likely want to use a 500-watt light. At minimum, use a 250-watt one. Many photographers use higher wattages as needed.

4

Take a light meter reading of the amount of light falling on your subject from your key light (optional). If it is strong enough to expose your film well, you can set up the next light. If it is not, add more key lights to the same side and in the same direction. Make sure to measure the spot where you want the most light, not the entire scene.

5

Add fill lights. These are lights on the opposite side of your subject from the key light. If you are using a light meter, add fill lights so that your meter reads 2 f-stops lower on that side. If you are estimating, add up the wattage of your key lights and use half the amount. Your subject is now ready for you to photograph.

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