If shutter angle 45 degrees, how much more light would you need for key exposure?

If shutter angle 45 degrees, how much more light would you need for key exposure?

• A. One stop more
• B. Two stops more
• C. Three stops more
• D. Four stops more

Answer: (B)

Shutter angle controls how long light is allowed to hit the film or sensor each frame. A smaller angle means a shorter exposure time, so the image gets less light. With a 45-degree shutter, the frame receives only 45/180 of the light compared to a standard 180-degree shutter, which is one quarter of the light. To maintain the same key exposure, you’d need four times as much light because you’re currently getting one quarter as much light. Four times as much light translates to two doublings (two stops) of light. So the correct amount is two stops more.

Shutter angle controls how long light is allowed to hit the film or sensor each frame. A smaller angle means a shorter exposure time, so the image gets less light. With a 45-degree shutter, the frame receives only 45/180 of the light compared to a standard 180-degree shutter, which is one quarter of the light.

To maintain the same key exposure, you’d need four times as much light because you’re currently getting one quarter as much light. Four times as much light translates to two doublings (two stops) of light. So the correct amount is two stops more.