Experiments
Gene F. Rhodes   09/15/03           home

(Other xperiments)

White LED Keylight: 36, 3mm, 25 degree LEDs and 18 resistors were assembled in a 46 x 9mm acrylic plastic disk retained with a metal snap connector device that attaches to a 9V battery. The main purpose was to provide photographic key lighting for small objects. Off color LEDs and epoxy contamination of the LEDs will limit this use. Because the 3mm LEDs are so tiny I lost control while cementing them in place. The secondary purpose was a white LED flashlight and it works quite well for that.
Reading Light: Head mounted 22 LED light assembly. Several uses, but the main purpose is to be able to read during frequent power outages. All of my 3mm LEDs are off color.

Minolta D7i Macro: The D7i requires closeup lenses for close macro work, so I used a modified lens hood to retain my Sunpak 622 ring flash head at the lens hood coupling. Presently using blue plastic foam to help support the ring head. Zoom is set to 200mm and lens switch to macro. The flash is set up in manual mode at ISO 25, f14 and 9 ft and the camera set to f8 and 1/60, also in manual mode. (The Minolta Ring Flash R-1200 should work well at very close range.) See 28mm and 200mm sample photos below.

Minolta D7i Flash Ring Light: For suitable macro images the lens thread must be used for closeup lenses, so I'm building an optical fiber cable (120, 1 mm) that connects to the popup flash and to a ring that is connected to the bayonet hood mount. The ring assembly includes the bayonet ring from a spare lens hood. The choice of 1mm fibers was a disaster. Too stiff to form properly, so the result was a kludge that I'm ashamed of. Decided to finish it anyway to test the design concept. The TTL flash functions properly as expected. I set the aperture at f8 for the 28mm macro shots and f9.5 for the 200mm macro shots. Using the internal viewer, I hand held the camera at closest range and focused manually in 4X magnifed mode. Closeup lenses +4 and +8 were used in both cases. Depth of field is very shallow at 200mm..... This setup works very well without the optical fiber cable, by using an external flash unit and bounce lighting.

19 mm Ring Light:  Miniature ring with 8 modified 5mm white LEDs installed in a 28mm filter ring.  The layout was for 9 LEDs, but one position was used for battery cable anchor and installation of resistors. The LEDs are frosted for smoother lighting and have a limited working range of 0.8-6 inches at ISO 400. 
Concentric Ring Light: A two section ring light consisting of eighteen 5mm white leds organized into a 17mm inner ring to flood near objects and dark holes, and a 39mm outer ring for more distant objects.The rings are 0.24 inch acrylic plastic mounted inside and outside of a modified 28mm filter ring. The working range is 0.8-24 inches, at ISO 400.
13 mm Ring Light: I discovered that my CP-990 ( in macro mode 14.7mm ) can peek through a 10mm hole without clipping corners. This inspired a new ring design using ten modified 3mm white LEDs ($39) mounted 1mm in front of the lens window. In this configuration the LEDs need not be tilted and are mounted in a 28-37mm stepup ring ($11) ... Provides lighting into small black holes .. Working range is 0.8 - 4 inches, with no other lighting.


Iridoscope2: To reduce the size of highlight reflections, six LEDs were modified to create point sources of light. The concentrating lenses were cut away to reduce the light source diameter from 5 to 1 mm. The improvement is obvious.
Iridoscope:  This hand built light assembly was created for photographing the iris of the eye. It is an extended eye cup containing two white LEDs, and a filter ring for camera attachment. The LEDs are tilted 60 degrees to provide side lighting for better iris surface detail and to move the highlights to the outer edge of the iris. This is an evaluation unit with simplified mounting.
Super Blue Ring Light: A lens-mounted ring with eighteen super blue (470 nm) 15 deg LEDs tilted at 30 degrees was custom designed for use in a microbiology experiment. It includes a green filter (508-512 nm) cemented into the coupling ring. (Blue light excites certain protein molecules and causes them to emit a fluorescent green light.) This experiment is to see if the Nikon CP-9xx cameras and a hand made ring light can be used to capture this effect..

White LED Ring Light: First effort in building a prototype light assembly using 24 "LED-50" bright white LEDs from The LED Light (see URL below). The LEDs have 50 deg beams and are tilted to focus on a spot 1.5 inch in front of the lens. If necessary they are adjustable by bending the LED leads to determine the final configuration. Working range seems to be 1-12 inches with amazing brightness, and daylight color. Four AA alkaline batteries are used for the prototype, but smaller batteries will suffice. A power switch is in the bottom of the battery holder. http://theledlight.com/led-specs.html A much cheaper source is. http://www.whitelightLED.com/ ..