A camera takes a properly exposed photo at F5.6 and 1/125 s. What shutter speed should be used if the lens is changed to F4.0?

검증된 단계별 안내

Understand the relationship between aperture (f-stop) and exposure. The f-stop value determines the size of the aperture, which controls the amount of light entering the camera. Lower f-stop values (e.g., F4.0) allow more light, while higher f-stop values (e.g., F5.6) allow less light.

Recall the formula for exposure adjustment: the exposure is proportional to the square of the f-stop ratio. Specifically, the change in light is given by \( \left( \frac{f_1}{f_2} \right)^2 \), where \( f_1 \) is the original f-stop and \( f_2 \) is the new f-stop.

Calculate the ratio of the f-stops: \( \frac{5.6}{4.0} \). This ratio will help determine how much the exposure changes when switching from F5.6 to F4.0.

Determine the adjustment needed for the shutter speed. Since the aperture is letting in more light at F4.0, the shutter speed must be faster to maintain the same exposure. Use the inverse of the square of the f-stop ratio to calculate the new shutter speed.

Apply the calculated adjustment to the original shutter speed to find the new shutter speed. Ensure the new shutter speed is faster to compensate for the increased light entering the camera at F4.0.

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주요 개념

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Exposure Triangle

The exposure triangle consists of three elements: aperture, shutter speed, and ISO. These elements work together to control the exposure of an image. Changing one element requires adjustments in the others to maintain the same exposure level. In this case, changing the aperture affects the amount of light entering the camera, necessitating a change in shutter speed to achieve proper exposure.

Aperture

Aperture refers to the opening in a camera lens that controls the amount of light that reaches the sensor. It is measured in f-stops, with a lower f-stop number (like F4.0) allowing more light than a higher number (like F5.6). When the aperture is widened (lower f-stop), the camera needs a faster shutter speed to prevent overexposure, as more light is entering the camera.

Shutter Speed

Shutter speed is the duration for which the camera's shutter remains open to expose the sensor to light. It is typically measured in seconds or fractions of a second. A faster shutter speed allows less light to hit the sensor, which is necessary when the aperture is opened wider. In this scenario, adjusting the shutter speed is crucial to compensate for the increased light from changing the aperture from F5.6 to F4.0.