Wednesday, March 21, 2018

Globe Flash

After my recent experiment with using a handheld flash for macro, I learned a few things. Most important of these things is that shadows are for artists. As someone who is mostly trying to take a whole bunch of high quality photos of insects in a hurry, shadows are not my friend. Ending up with a shadow covering an important part of an insect for identification is a real problem with that setup. Also it was bulky and a lot of work.

After some research on alternatives I ran into a clever flash which uses a globe shade off of a lamp as a diffuser. This made a whole lot of sense to me since the best diffusion comes from a sphere of light around the subject. I can't quite get there with a globe cut in pieces, but I can get a whole lot closer than with just about any alternative. The globe also reduces shadows since light is coming from a bunch of angles.

So I bought a six inch acrylic globe and went to work. 

There are a few challenging parts to making this setup work. First was cutting acrylic. This isn't necessary if you can find a hard plastic globe, but acrylic ones are much easier to find so I bought one of them. My first attempt  was with a hack saw. With sufficient patience this may work, I got tired of cutting though, rushed through, and cracked it. After that I tried cutting with a dremel tool. That seemed to work well.

The next problem is how do you attach the globe to the camera? My first thought was to order a 3D printed attachment to where the lens hood connects. This is probably the right answer, but I got lazy since this would require some real work. Eventually I realized a simpler solution is to buy an adapter ring from 62mm(the lens threads) to 77mm(the diameter of the globe). Then I epoxied the globe to the adapter:
 I am not quite sure how durable the epoxy/adapter connection will prove. If it does hold up though, this is a great solution for how to connect the globe.

After a bit of use, I realized  another problem. The shade blocks too much light! What ends up happening is that the background turns white because it is not shaded, and the area focused on is often too dark. Worse, the setup only works at minimum focus distance! Once the subject is further away, there is a big bright area which is not blocked by the globe, and a dark area which is.

A paper towel seemed to fix these problem, although using a 10 or 12 inch globe would probably be a better solution.

I have only used this setup two days, but so far results have been remarkable. To use an example everyone knows, here is a photo of a fruit fly. Extra diffusion from the wall, probably made it better than it otherwise would be but still it is impressive results from such a low cost flash:


This gets even more impressive when compared side by side with a photo using the same lens/camera and the Sony Twin Flash which was four times the price as this flash. The bright spots from reflection stand out much more with that setup:





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