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Emulating bare bulb with speedlight - or - Describing the temporal evolution of a flash of light in Einstein-Minkowski spacetime

Published February 12th, 2013

Couple days ago I read an article called "3 Ways To Bare Bulb your Flash" from DIY Photography ( and started to think if there is a fourth option which would not cut as much light as Omni-Bounce/Wax-Fenning and would not require me risking my life with capacitors.

Yesterday morning I woke up with a simple idea and did some drawings while drinking my morning coffee about how the fourth option could be done. Items required were broken down umbrella, (some wire iron), adhesive reflecting contact paper and some hard plastic. (Umbrella was needed to get the wire iron and the "sticks" to build the frame that would hold the bulb-emulating reflector in front of the flash.)

First attempt was done with mirror contact paper only and tested against Omni-Bounce, and it worked out quite nicely, except it wasn't stable and light spread was uneven (see Test 1 in image "Reflect'O'cone aka. LightCone test 1"). In test 2 some hard plastic was added to give the reflector even form. As you can see from the image, that rough wire-model test was more or less a failure - it didn't reflect enough to the sides and cut some light. Some of the problems could have been corrected by coating the plastic totally with the mirror contacts, but I decided to think something else. Oh, well, more coffee and back to the drawing board.

Enter the LightCone aka Reflect'O'Cone.

Again, simple ideas work the best - making a simple cone from the mirror contact paper and cutting the tip of the cone off (making a small hole in the bottom of the cone) resolved the problems encountered in the previous tests. In the second image the Cone is again tested against the Omni-Bounce. The Reflect'O'Cone seems to spread the light to the sides quite evenly and it does not cut nearly as much light as the O-B. Two landscape-oriented images in the image "Reflect'O'Cone aka. LightCone test 2" were taken with auto white balance, while the two portrait-oriented shots were taken with white balance set to "falsh" - which brings out how the Omni-Bounce changes the color of the light.

There were only two little easily correctable problems in the Reflect'O'Cone when compared against Omni-Bounce: First, the R'O'C does not spread as much light down as the O-B does. That can be easily corrected by altering the the width and the height of the cone. Secondly, the cone seems to cast a shadow to the ceiling. That can be easily corrected by making the hole in the bottom of the cone bigger and using material in R'O'C that is reflective on the both sides. The trick is to get the hole big enough that it lets enough light to pass straight, and small enough that it lets enough light to be bounced to the sides.

Reflect'O'Cone pros:

+ Cheap

+ Light

+ Easy to make

+ Does not cut as much as light as Omni-Bounce

+ Does not kill you with electric shock

+ Does not alter the color balance of the flash

+ Easily adjustable (just make bigger or smaller cones to adjust the light spread)

Reflect'O'Cone possible cons:

- Flimsy (-> needs more product development)

- Casts shadow to the ceiling (-> make a bigger hole to the bottom of the cone - fixed!)

- Does not bounce enough light backwards (-> alter the length, width and angles of the walls of the cone - fixed!)

- Not as good as real bare bulb

That's it, now go and make a better version of it - and drop me a line to tell how it works! :)


Reflect'O'Cone aka. LightCone test 1

Test 1 reflected more light to the side than the Omni-Bounce, but the light spread was uneven. Test 2 didn't work out at all.


Reflect'O'Cone aka. LightCone test 2

Cone shaped mini-reflector on top of the flash does the trick!

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Jay B  over 5 years ago

This is a neat idea, big fan on the science/math behind the initial idea, thinking about doing a half cone so I could make it more directional but still have the conical shape of light

neiltsubota  over 5 years ago

This is a GREAT idea. I'm going to my local hardware store to see if I can find this "reflective" contact paper.

Janne Kaakinen  over 5 years ago

Oh, and for the title of this post, check out Wikipedia page on light cone ( :)