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| p.1 #20 · A Fruit Juice Container Flash Defusser, laugh if you like! |
To get a better understanding of what is causing the diffusion in your DIY creations try the same test set-ups indoors then outdoors at night where there is no bouncing "spill fill".
Speedlight modifiers which generated both a dominant 45 degree vector of light down off a ceiling and a lot of omni-directionall fill do the best job of mimicking flattering natural light's downward modeling (getting it past the brow into the eyes) and the 3:1 highlight / shadow (reflected) contrast of key:fill we typically perceive at being "normal".
What happens when shadows get lighter? The light seems "softer" than that 3:1 baseline normal ratio. What happens when they get darker? The mood of the subject or environment no longer seems "normal" causing the viewer to infer from the shadow tone clues the subject is moody, sad, aggressive, or in a quieter /more hazardous place than normal. There are lots of other perceptual clues of course, but if you were to put a flattering key light pattern on a face (i.e., short lit oblique view) and change only one thing, the amount of fill and shadow tone, the impression about environment and subject mode will change by inference in the viewer's brain when it interprets the 2D contrast pattern. The changing ratio will not change the overall perception of it's 3D shape much until the shadow detail is eliminated completely. Even then the brain will discern 3D shape from the highlights alone if they fall in the same places natural downward key lighting puts them on the top of round surfaces between 10 and 2 o'clock on a clock face.
What makes lighting in an image "look right" for a situation is when all the clues agree. For example if a person is smiling and looking straight into the camera shaded eye sockets and dark shadows seem out of context with the come engage with me body language. Shaded eyes say "you can look but don't bother me." But if the person is frowning and looking away a 4:1 ratio creating darker than normal shadows and shaded eyes are the lighting clues needed to match the expression body language signals. That's why there's no one size fits all modifier strategy and single flash solutions where the ratio is function of spill fill don't offer as much creative control as two directly aimed independent key and fill sources will. You need directional control of key light relative to face to put light in the eyes or not when you want to, and independent control of the fill to control shadow tone and the implied mood / environment as one that is average/ normal or not.
Those are the perceptual goals to think about when evaluating the results the modifier and space it is used in create. What is the modeling key light vector direction and intensity. Where are the fill vectors coming from and why, and how strong are they relative to the key vector?
One of the reasons I always use a bracket, even when adding my modifier, it to create the downward natural modeling key vector in situations where I can't bounce more light off the ceiling than forward to create it. It's the 45 degree downward direction of the key light vector that places the highlight clues on the face and controls the angle of the shadow clues which the brain interprets as "normal" 3D shape because that's the angle of natural light relative to the face when it get's past the brow into the eyes. Without the bracket the modifier will create the same amount of "spill fill" but the highlight clues will be as low and unnatural as those produced with direct flash in the hot shoe.