The Fluor Rainbow

Fluorescent subjects are one of the most impressing themes that can be photographed. The reason is simple: Under ultraviolet light they glow very brightly, like if they were illuminated with a very bright bulb, but as ultraviolet light is invisible to our eyes the glow appears to come from the subject itself, as if it was emitting the light without any help. Today I’m explaining how to get one of the nicest pictures I have made in this theme: The Fluor Rainbow.

The Fluor Rainbow
f/5.6; ISO 100; 1.6 secs.

In the picture 13 glass vials are filled with 13 different chemical compounds. The vials are hermetically closed and the air inside is pure nitrogen, without any trace of oxygen. Those compounds have a common property: they all absorb ultraviolet light from the ambient and re-emit it as a form of light that we can see. Each of them emits the light in a different color, which is what allows us to create the rainbow effect.

In order to capture the light the compounds are emitting it is necessary to work on a dark environment. The amount of light that they emit, although enough to be visible to the naked eye, can be overflowed by the ambient light and if this happens we won’t be able to see the effect. Reducing as much as possible the ambient light reduces the competition with the emitted light, and the sensor of the camera will only capture the light we desire. So in order to arrange the elements in the table and adjust parameters we can use light, but once the capturing process starts, it is necessary to make the room as dark as possible.

Working in a dark environment also imposes limitations. The use of a tripod is a complete must. We will need to acquire light for periods of time longerthan 1 second, so the hand movement will be enough to obtain a blurred picture. The tripod stabilizes the camera and provides us with the ability to lengthen the times longer (5-15 seconds are reasonable amounts of time for this kind of pictures). To increase the sharpness of the picture, also some tricks are advisable:

  • Activating the mirror lock-up, so the mirror lifting movement is detached from the sensor exposition. When we push the trigger, the lifting movement of the mirror can make the camera tremble for a couple of seconds. As the shutter speed is slow, that tremble can cause blur in the image. Lifting it in advance before taking the picture improves the quality of the picture dramatically.
  • Use a remote trigger or a delay. The ideal choice is a remote trigger, so we can lift the mirror without touching the camera (and making it move) and after a few seconds activating the shutter without touching it again. Mirror lock-up would be useless if after locking it we move the camera pushing the trigger button. If you don’t have a remote control, activate the delay of the camera between 2 and 10 seconds. When we push the trigger the mirror will rise immediately, but the camera will wait the programmed period of time before taking the picture, so vibrations will dissipate before starting the light acquisition.
  • Focus using the Live View mode. Before turning off the lights activate the LV mode and zoom on the vials. It is difficult to focus on soft glass, due to the lack of contrast areas, but you can focus very well in the caps. If your subject doesn’t allow this, just put another object on the side of your main subject and focus on it, as the focus plane of this dummy object will be in common with the main object. Also, because you have a tripod and you can use shutter speeds as slow as necessary decrease aperture to around f/8, so you have enough depth of field to capture the entire subject and correct any minor maladjustment in the focus.

Taken all of these steps into consideration, is time to turn off the main lights and turn on the UV light. As I explained before the UV light is not visible to our eyes, so we will be filling the room with light, but we won’t see any increment of luminosity… almost. Most commercial UV lamps are not perfect, and they provide a little amount of blue light. When we turn on the light, we will see that light, and so will the camera. We will deal with this in a moment. Also, the camera sensor is slightly sensitive to UV light and can capture a bit of it as a bluish haze. In order to avoid this it is a good idea to equip the lens with an ultraviolet filter that blocks the UV light and only allows the visible one to pass (probably, you will already have one of those mounted on your lens to protect them). If you are wondering where you can find an ultraviolet light try your closest bulbs store, and ask for a black light. They are used very commonly on pubs and discos as decoration. I got mine for less than 20 euros.

Now you can take the pictures and enjoy playing with the parameters.

After taking the picture, some software corrections are needed to achieve a better look. You will need to correct the white balance in order to erase the blue component caused by the blue light the lamp emits (and also the UV mist if you didn’t use the filter). Although some people do it against a grey card I have found that usually this method overestimates the blue component. Adjusting manually, just making the colors approach the ones you saw when you were taking the picture, usually provide very good results. After that, everything you do belongs to the creativity field: you can adjust curves, modify saturation, tint the image, or any other modification you desire.

I took the picture using some exotic compounds that are not available for everybody, but that doesn’t mean you cannot have fun with this technique. Many objects around us are usually fluorescent. Money, passports and any official ID card are usually modified with fluorescent dyes to avoid falsification, just try to expose them to ultraviolet light and see what happens. Also, some gems or stones fluoresce in bright colors when exposed to this kind of light. Natural products, like oils and fats tend to fluoresce in yellow, so visit your kitchen or bathroom with the lamp to see what you can find. Chlorophyll, the pigment that makes leafs green, fluoresces in red, try using the light on a plant or vegetal. And of course, the more creative and interesting objects are fluorescent paints, dyes and make up. You can use them to paint anything and make it visible under ultraviolet light. Try a portrait with a face that uses fluorescent make up, or a body painted with them. The results are amazing.

As I told you previously, these vials are closed in absence of oxygen. Other day I will show you what happens when we open the cap and expose them to the air.

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