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<blockquote data-quote="WayneF" data-source="post: 229626" data-attributes="member: 12496"><p>I doubt the bounce suffers red shift unless the ceiling is accelerating. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> Joking, but no, I am not aware of anything except it can take on a color tint reflecting from a non-neutrally colored surface ( bounce it on a red wall, and it will become significantly red). Many ceilings are white enough to not be a big problem, but use of a white card to be sure is always helpful to get White Balance exact. Getting white balance and exposure just right is always that last straw that makes so much difference.</p><p></p><p>We certainly do lose power from bounce. The travel path up and down (and the trig to go forward to the subject too) is a significantly longer path than the direct line, so inverse square law makes a difference. Also the ceiling has a reflection coefficient. A white popcorn ceiling would be higher that a 18% card, but not very near 100%. The best smooth white card is only about 90% reflectance, so I'd guess maybe 65%, but I really have no idea. Dispersal over the wider room is also a major factor, dispersal dilutes the beam, it takes power to fill a wide area to the same brightness as a small concentrated beam. Depends on the situation of course, but overall, common bounce probably often needs about three stops more power than direct, which is 8x power. We can't ever have too much power for bounce. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p>We usually called it two stops more for bounce, back in the old days of film and flash bulbs and no metering and no test shot results. The only reason it worked was because negative film had so much more latitude - it was hard to do much wrong.</p></blockquote><p></p>
[QUOTE="WayneF, post: 229626, member: 12496"] I doubt the bounce suffers red shift unless the ceiling is accelerating. :) Joking, but no, I am not aware of anything except it can take on a color tint reflecting from a non-neutrally colored surface ( bounce it on a red wall, and it will become significantly red). Many ceilings are white enough to not be a big problem, but use of a white card to be sure is always helpful to get White Balance exact. Getting white balance and exposure just right is always that last straw that makes so much difference. We certainly do lose power from bounce. The travel path up and down (and the trig to go forward to the subject too) is a significantly longer path than the direct line, so inverse square law makes a difference. Also the ceiling has a reflection coefficient. A white popcorn ceiling would be higher that a 18% card, but not very near 100%. The best smooth white card is only about 90% reflectance, so I'd guess maybe 65%, but I really have no idea. Dispersal over the wider room is also a major factor, dispersal dilutes the beam, it takes power to fill a wide area to the same brightness as a small concentrated beam. Depends on the situation of course, but overall, common bounce probably often needs about three stops more power than direct, which is 8x power. We can't ever have too much power for bounce. :) We usually called it two stops more for bounce, back in the old days of film and flash bulbs and no metering and no test shot results. The only reason it worked was because negative film had so much more latitude - it was hard to do much wrong. [/QUOTE]
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