Affordable high-CRI lighting for large backlit light boxes
Asked 12/20/2010
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I’m building several large, very bright light boxes for backlit prints and need a lot of lamps, so cost matters. Good color reproduction is also important. Ideally I’d like CRI 100, or as close as practical. What types of light sources are suitable for this kind of use, and what are the realistic trade-offs between cost, brightness, and color quality?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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You're only going to get 100% CRI out of tungsten lights or special purpose fluorescent tubes. The tubes are going to be expensive, not to buy but to install seeing as you need special fittings with transformers, starters and chokes. You might be able to get a bulk discount on fittings designed for office buildings however the tubes are likely to be long to fit behind a print in any case.
The best you will get out of a CFL (compact fluorescent lamp) is about 90, though I've heard talk of higher. That may be good enough for you, it would certainly be cheap to run but the bulbs aren't cheap.
The final option is daylight balanced tungsten bulbs which will give you 100 CRI, will be cheap to buy if you can find them. Which country are you based in? The EU is quickly making it illegal to sell tungsten bulbs but you can still find them in quantity with some retailers (at least this was the case last time I looked). This option will be most expensive to run, however.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
15y ago
0
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For true CRI 100, your realistic options are tungsten lamps or certain special-purpose fluorescent tubes. Tungsten gives excellent color rendering and is usually inexpensive to buy, including some daylight-balanced tungsten bulbs if available in your market. The trade-off is efficiency: they cost more to run and produce more heat.
Special high-CRI fluorescent tubes can also work, but the tubes themselves may not be the main cost. The fittings and installation can be more expensive because they need proper fixtures/ballasts, though long tubes may suit large light boxes well.
Compact fluorescent lamps are the cheaper-running alternative, but they usually top out around CRI 90 rather than 100. That may be acceptable depending on how critical your color matching is.
So in practice:
- Need true CRI 100: use tungsten or specialist fluorescent.
- Need lower operating cost: consider CFLs, but expect slightly lower color accuracy.
- For large boxes, long fluorescent tubes may be physically convenient if you can justify the fixture cost.
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