What in the world are Foot Lamberts, and why do I need to eat up precious brain space understanding them? Well, hopefully, we can help make their impact on outdoor movie entertainment easily understandable. Because frankly, who doesn’t love spending time with family and friends watching your favorite flicks on a big screen? We sure do! Add that same enjoyment to the comfort of your backyard, and you’ve got entertainment and lasting memories to boot! It is easy to detract from the possibilities with less than stellar movie quality.
Believe it or not, there are lots of things to consider to get the optimal viewing experience. While these things certainly aren’t requirements, why not get the most out of them if you spend hard-earned money on a quality outdoor projector and outdoor projector screen. This optimal viewing is where Foot-lamberts come into play.
So What Are Foot Lamberts Already?
Simply put, a foot lambert is a unit of measure used to measure the intensity of the light of images on a projection screen. If the math used to calculate a foot lambert is interesting to you, check out the Wikipedia page. So how does this concern your setup? Well, watching a movie in the solace of your favorite outdoor space isn’t quite the same as watching in a light-controlled movie theater or family room. Ambient light from any number of sources will directly impact your ability to see the image. For example, The lights over the deck of your neighbor’s house that for some reason never, and I mean never, turn off; string lights hanging around your viewing area, or a nice relaxing fire pit. While often not excessively bright, these examples, and many more, can cause the light to appear dim on the screen.
You’ve likely seen it before, television on in the middle of the day with the sun shining in, you can’t see much. The same holds for watching movies on an outdoor projector. The image gets washed away in the presence of too much light. Having the foot lamberts set correctly based on the ambient lighting will allow for a quality image and viewing experience. So what are the appropriate foot-lamberts for optimal viewing? Well, I’m glad you asked. Or maybe you didn’t, but either way, I’m going to tell you, so buckle up.
According to the SMPTE 196M standard, for darkened rooms, there should be a minimum of 12 foot lamberts up to a maximum of 30 foot lamberts, with the sweet spot at 16. However, in our case, we are not in a darkened room, nor can we guarantee consistent ambient lighting. The table below shows the general recommendation for foot-lamberts based on the ambient lighting conditions.
|Ambient Lighting Condition||Recommended Foot Lamberts|
|Dark||16 – 29|
|Low Ambient Light||30 – 39|
|Medium Ambient Light||40 – 59|
|High Bright Ambient Light||60 or higher|
Fortunately for us, any quality outdoor movie projector will have brightness control allowing for fine-tuning of brightness that fits your viewing needs. This control saves us the trouble of going through and calculating the necessary foot lamberts, but the optimal viewing brightness (luminance) is mathematically derived. I guess my old math teachers were right; you’ll never escape math. Happy viewing!