In image 6 I remained in TTL-BL mode and moved the focus point to the far right so the rope below the hats would be in focus. Immediately you see a change in the flash power. The statue is now overexposed and the background is much brighter. This is what has been causing even experienced photographers to think that the focus selection has an effect on flash power. However, the change is not being caused by moving the focus points. It is being caused by the change in focus distance. In this image the hats are about 15 feet behind the statue, and in TTL-BL mode, the distance is the prime factor that is used to set flash power. So, the farther distance caused the power to increase.
In image 7, I left the flash in TTL-BL mode, and switched off the auto focus and moved the focus point back to the statue. the important thing to notice is that the exposure of this image is identical to the previous image. This proves that moving the focus point does not affect flash power.
In image 8, I moved the focus point back to the hats. Again the exposure did not change.
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