The greater the distance between the light source and the subject , the less the light will illuminate your subject 

As a general rule ofg thumb, light dims or falls away as the square of what distance it is from the subject, In other words, if you double the distance between the light source and your subject, just one quarter of that original light will make it ot hte subject. 

Another thing to keep in mind when moving around your ligth source- and/ or your subject -as you snap your photographs! Rememer also that bouncing the light actually adds to the overall distance it travels adds to the overall distance it travels before reaching the subject, and thus generates some dimming also. 

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