This is our entry in Dutch goes the Photo!’s Tuesday Photo Challenge – RGB.
This photo was taken while experimenting with the additive properties of light for a photography class project. The objects photographed were one small black circle made of cardstock and several white cardstock circles (small, medium, and large), plus a string of blue LED lights.
Equipment: Three color gels were used to represent the three primary additive colors. The gels used were Rogue Lighting Filters Just Blue (f-stop loss 2 1/3), Bright Red (f-stop loss 3 1/2)., and Moss Green (f-stop loss 1 1/2). The flash unit used was a Yongnuo YN-568EX II 4-Channel TTL Flash Speedlite for Canon E-TTL/E-TTL II Cameras. A string of blue LED lights was used as another source of the color blue.
Procedure: A large rectangle of black velvet was laid flat on the floor, and an arrangement of paper objects was laid on top of the velvet. The camera shutter was opened. An external flash unit with a color gel was fired once from a height of approximately 30 inches. The objects were rearranged. The flash was fired again, this time with a different gel. The objects were rearranged again. The flash was fired for a third time with the last gel. The objects were removed from the velvet and the string of blue LED lights was shaken over the black velvet. The camera shutter was closed.
Results: The purpose of the black circle was to create a black hole (no color) in order to negate the color added by the gel being flashed. The three secondary colors (cyan, magenta, yellow) are visible at the overlaps of pairs of the three primary colors (red, green, blue). The color white is seen at the overlap of all three primary colors.
(A fun exercise is to deconstruct the three arrangements of objects used, by using the color addition formulas: green+red=yellow, green+blue=cyan, blue+red=magenta.)
The blue from the light string added color and increased intensity to the otherwise solid colors. Because the lights are closer to the lens and moving, this part of the image is not as in focus as the circles. The glow from the blue LED light string does not seem to be combining with the color of the circles as expected. For example, the glow on the red circle is not magenta. This could be because the camera is photographing a solid object (the light string), rather than recording colored light.
This photo was taken on August 1, 2016. The room was in almost complete darkness and the camera was on a tripod. Specs are:
Canon 100D, ISO 100, f/11, BULB, 34 mm