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My First Light Box. How do I decide?
A few things to consider. The most popular size light boxes are 10" x 12", 12" x 18" and 18" x 24". You need to think about what you want to use a light box for and how much studio/lab space you have. If you go with a larger unit you have the luxury of laying out more than one project at a time. Our light boxes, within a certain size, are functionally the same. The differences are handcrafted wood vs. white powder coated steel vs. vinyl laminate cabinets, glass vs. acrylic work surface and handle vs. no handle. If your considering an even larger size, think about what happens when your sitting at the light box. I recommend our BL1836 over our BL2436, because the additional 6" of view area is away from you. This means you have to get up out of your chair to view that region of the light box. At the same time, there are applications where the BL2436 is best. If it's still unclear call me and we can talk 1-805-473-1042. Then there is always the custom route. If you want a little of this and some of that, we can probably do it.
LED vs. Fluorescent?
The industry is moving away from fluorescents, with good reason. LEDs have lower energy usage, longer life, are cooler operating and dimmable. Fluorescent flicker is a non-issue. Pretty much LEDs are better across the board, with the exception of intial cost. Which is offset by lower energy consumption, longer life and being maintenance free. When ordering check to see which of our units have changed to LEDs and which are yet too. In most cases we can go LED in the light box you want.
5000 Degrees Kelvin. What does that mean?
Originally the photographic market didn't have a standard. They looked around and adopted the standard from the printing industry. The temperature refers to the color of light. For example, Cool White lighting is around 4100 degrees Kelvin. The idea of 5000 degrees Kelvin is to mimic northern exposure midday sun light. It is achieved by blending three different phosphorus together. A current of electricity is arced through the lamp and excites the phosphorus and presto you have light. Together the three phosphorus create a graph that comes close to the graph created by northern exposure midday sun light.
CRI Rating, Color Rendering Index. What's up with that?
CRI is somewhat subjective, it tells us how clean or pure the light is. It is a system of looking at prints or transparencies, deciding which light gives the best results and assigning it a value from 0 to 100. 100 being the best.
Color Comparison. How to achieve repeatable results?
This is the meaty one. There are so many things that effect lighting. The color of your shirt, the ambient lighting, the batch of lamps produced by the lamp manufacturer, the light box you're using. If you read about 5000 degrees Kelvin and CRI rating above, the idea is to approach northern exposure midday sun light. All this being said, when you have a CRI Rating of 80+ or better your in the ball park. The key to color comparison is to always do your final viewing in the same way on the same light box. By doing this you learn the equipment you're using, it's strengths and weaknesses and you reduce the introduction of error. It doesn't matter that there are errors, that's a given. The secret is BE CONSISTENT! Use the same light box for final viewing.
Lamp Life. Just how long is it?
To give a comparison LEDs last on average 25,000 hours or more. Fluorescents last 7,000 hours and that is 7,000 hours to failure and you should replace fluorescents long before failure, when doing color comparison. The way fluorescent lamps are rated for longevity is the following: Turn the lamp on for three hours, turn it off, turn it on for three hours, turn it off over and over until it fails. As stated above, when doing color comparison the lamps should be replaced long before failure. A good rule of thumb is based on amount of use. If you're using your light box on a daily basis, change the lamps once a year. If you're using your light box a couple times a week or less change the lamps every other year. Avoid turning the lamps on and off. This wears out the element that heats up and excites the phosphorus that produces the light. Also burn new fluorescent lamps in for 10 to 15 minutes before doing color comparison.
Intensity. Is there a standard for intensity?
Yes, it is a broad range 321-497 footlamberts. If the intensity isn't enough you loose detail, if to bright your transparency appears washed out. Interestingly, as lamps age, they dim. This has the appearance of the light changing color, in reality the lamp is still the same color temperature. Bottom line the most important instrument is your eye. What you perceive visually is the only thing that matters. There are different units for measuring light and they aren't readily convertible one to the other i.e., candela, candle, footcandles, footlambert, lumens. These measure different aspects of light that don't necessarily relate to each other.
Eye strain. Is there anything I can do to reduce eye strain when using my light box?
Your local art supplies store carries sheets of hard board (frequently used to mat pictures placed in picture frames). Use the hard board when viewing objects of similar size. Cut the hard board to fit the outside edge of your light box. Then cut a window in the hard board to the size of the objects being viewed. This blocks unneeded light from around the object being viewed. What happens is the iris of the eye contracts to cut down on bright light entering the eye, which can create eye strain. You can make a few different size hard board windows, so you can swap them out when viewing different sized objects.
High Frequency Light Boxes. Why would I want one?
This question has been rendered mute with the introduction of LEDs. If you are staying with fluorescents then read on. If you plan to use your light box as part of the lighting, while doing a photo shoot, then you would want to consider a high frequency light box. Conventional fluorescent systems operate at sixty cycles a second. What this means is the lamp is turning on and off sixty times a second. When operating properly the on/off cycle is not visible to the eye, but it is to a camera. It's when it drops below that speed, we see the flickering light we associate with fluorescent lamps. Our cameras pick up this slow cycle even when the lamp is working correctly. So you take a picture and there are shadows or the camera can't focus, it's because of the normal characteristics of fluorescent lamps. High frequency light boxes operate at upwards of 25,000 cycles per second. This is so fast the camera can't pick it up, thus no shadows or wandering focus.