As our class at West Coast School with Jesus Padilla progressed, we ventured over to the south end of the USD campus to the reflection pool. While the sun was relatively high, we were still able to utilize the it as a back light for our lovely model, Sara. Our next step was to measure the ambient light level in order to set our base exposure. With his trusty Sekonic light meter in hand, Jesus measured the scene illumination.
- The scene measured in at ISO 100, shutter speed at 1/125th and an aperture of f-11.
- This translates to an Exposure Value of EV-13, 2 stops below full daylight.
- As our model was back-lit, we would need a minimum light value from the CL-600X flash unit of f-11.
- The Flash Guide Number of the CL-600X with a 36" Octagonal Soft Box at full power is GN 90-ft. To determine the flash to subject distance, divide 90/f-11 = 8.2 feet.
- The goal is to bring the light as close to the subject as possible and still be out of the camera frame.
- With the light positioned approximately five feet from our model, Jesus set the output for f-11. Applying the Guide Number value of 90/5-ft would produce f-18 light. Therefore the power setting required was 1/8th and 2/3rds to produce f-11 light at 5 feet.
Jesus Sets the Light Output
Our model Sara, by this time a little weary of the long walk to the reflection pool, waits for the ready prompt to strike a lovely pose.
Our position for getting this shot was at the far end of the reflection pool. This required a long lens to focus the shot on our model. In the title photograph for this article, my lens was a 135mm f-1.8 Carl Zeiss on a Sony A-99 Mk I.
The scene measured and the light set, all that remained was to share the remote trigger with fellow students, compose and get the shot.