|16th of March 2009 (Mon)||#1|
Join Date: Mar 2009
Glow in the Dark Photography
Objects and paintings that glow in the dark make unique photo subjects. However, like fireworks, lightning, and other self-illuminating objects, they pose serious complications for the photographer. This article discusses the issues regarding phosphorescent photography and offers solutions and tips.
Fluorescent vs. Phosphorescent
Fluorescent materials instantly convert ultraviolet light to visible light. This is often referred to as day glow or black light paint. Phosphorescent materials store light and release it slowly, often referred to as “glow in the dark”. Fluorescent objects should be photographed while under a UV light source. Phosphorescent objects should be photographed just after being charged with a UV light source. The rest of the information in this article focuses on phosphorescent materials only. There are many chemical varieties of phosphorescent materials, such as strontium aluminate and zinc sulfide. Other than color and brightness, the variations are irrelevant to the photographer.
Tripod, Manual Focus, and Macro
It has been my experience that the typical camera's auto focus does not work for taking photos of glow in the dark objects. I suggest that you set the manual focus before turning off the lights.
Due to long exposures, I highly recommend that you use a tripod with a remote.
Often, people get too close when trying to photograph smaller glow projects like watches, flashlights, and knives. The macro setting allows you to get closer. However, I have found that moving the camera back to at least 4 feet is best.
Particles and Shadows
All glow in the dark items are created by putting phosphorescent particles in a clear medium such as paint, glass, wax, or plastic.
In most cases, these particles are very small, averaging about 30 microns each. When charged, only the surface of the particle that is directly exposed to light will glow. The opposite side of that particle will remain dark.
To the photographer, this means that you need to have your charging light at the exact same angle as your lens. Otherwise, the glowing area will look dim and may get a speckled appearance due to the tiny shadows.
Using cable wraps and masking tape, I have found that making a sandwich of my camera lens between two 2 foot black light bulbs attached to my tripod works best.
I have also used sponges to "stack" the black lights on a table with enough room between them to place my camera lens.
For clarity, here is a simple drawing of my setup:
==== black light
==== black light
When taking pictures of a glow in the dark object, you definitely want it to be as bright as possible. Phosphorescent pigments loose 75% of their brightness within 30 seconds of removing the charging light. Therefore, you want to use the brightest and most efficient charging light possible. You want to allow the object to get a full charge. You want to turn off the charging light and take the photo as fast as possible.
To accomplish optimum results, use two inexpensive 2 foot black lights hooked to a power strip. Set your camera up on a tripod, preferably with the lens between the black lights. Turn on the black lights for 10 minutes. Set your manual focus. Turn off the room's overhead lights. Turn off black lights using switch on power strip. Use the remote to immediately snap photo.
It is rather easy to take a photo of just the glowing elements of an object in pure darkness. However, seeing the tiny dots of a watch hand surrounded with black is not appealing. The ideal photo would show the watch as photographed normally with the glowing dot at a slightly brighter contrast.
This can be accomplished a variety of ways. The simplest way is to take a "glow" photo in darkness and then take a regular photo. Mix the two in a program like Photoshop with the regular photo slightly darkened. While simple, is this cheating?
To recreate this within the camera, set a very small aperture and long exposure. Take the glow picture as normal. During the exposure, fire off a flash unit that is set for about half of the exposure that a regular flash picture would need. You can do this by setting the flash unit to auto and set it to match the camera's aperture, but double the ISO setting.
While it is possible to setup some cameras to do this properly with a hot-shoe mount, it is easiest to do this with a non-dedicated flash unit.
In order to avoid grainy pictures, stick to slower film speeds like ISO 100 or less.
Aperture and Exposure
I started taking "glow in the dark" photos with a Canon Pro1. In my first session, my subject was a bottle of green glow in the dark paint. I took over 100 photos using different settings to finally find the optimum setup. I then moved on to a bottle of red glow in the dark paint. I quickly found that my settings were useless and went through the process again. Next, I took a photo of a rocket painted with the green paint. Once again, I had to practically start from scratch on the settings. At that point, I realized that the camera in auto mode was able to match my best attempts in all three cases.
Over the years, I have simply given up on trying to outperform auto mode. If someone can provide insight to manual settings for glow in the dark subjects, I will happily amend that information to this article.
In the meantime, save yourself the aggravation and give auto mode a try.
Visible Light Filters
Due to the quick loss of initial brightness for glow in the dark items, the ideal situation would be to take the photo with the charging light on. However, most ultra-violet lights emit some visible light, typically purple. Therefore, if you take a photo with a black light on, you will get a purple hue. To solve this, you can cover the black light bulb with a "visible light filter". This will only allow true ultra-violet light to pass. You can literally look at the bulb through this filter and not tell that it is on. These filters are ideal for videography. Unfortunately, visible light filters are extremely expensive and degrade quickly with usage and age.
This document is modified regularly. The most recent version is kept on the Glow in the Dark Forum in the "General Projects" section. If you have ideas to improve the information, we encourage you to post your suggestions to that forum.
This article was written by Daniel Clark (Skylighter), Senior Technician at Glow Inc., which sells high-end glow in the dark paints and powders.
Copywrite Glow Inc. 2009. Feel free to use or reprint this article in its full unedited version.
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