来源: 如何在白天做视频投影-布莱尔尼尔-中等

——你不能. 这是一个严肃的点击诱饵标题.

I’ve been in audio visual stuff for a while and still get requests or questions about doing outdoor projection during the day. 不幸的是, 直到威尼斯人电子游戏发明出超能量光炮或者反光暗影激光飞船, 这在短期内是不可能发生的.

This write up will deal more with the hypothetical of “What it would take for an electronic light to be perceived as brighter than the sun?“这是一个很好的时间来说明我不是一个科学家——这只是一个有趣的思想实验. 公平的警告,可能会有不止一个不准确的陈述或概念随之而来.

首先,威尼斯人电子游戏需要回答“亮度是如何测量的。?” — then we’ll get into the hypotheticals of how much brightness we would need to compete with the sun.

有许多不同的测量光的方法, 下面是一些与这个思维实验相关的例子:

参考维基百科中的lux读数示例:

要实际获得这些测量值,有几个可用的工具. 我用一个 照度计 亲自去看看. 这些光度计大多用于摄影行业, 但它们在很多其他领域也很有用, 从园艺, 博物馆照明和其他.

和我的照度计, 我的读数在90之间,000年和110年,6月纽约晴朗的一天,000勒克斯. 移动到树荫下和获得间接光线通常在3之间,000–9,000勒克斯.

简化假设

先把一些事情弄清楚, 有一些已知的事情威尼斯人电子游戏只需要做一些假设, 或者忽略威尼斯人电子游戏的计算. 第一个, 投影仪 are typically made to project in a 16:9 aspect ratio which is going to make our calculation for lumens per square (1:1) meter a little more challenging, so since this is a hypothetical exercise anyway — we can just assume 投影仪s are going to cover a square and not a rectangle. 其次, 投影仪 manufacturers have pretty different standards on what constitutes a lumen (some follow a standardized ANSI lumen measurement). We can also assume we’re talking about black to pure white here as different colors have different perceptual brightnesses 对威尼斯人电子游戏的眼睛. Full color images will potentially need even more light to appear vivid than just black and white gradients. 最后, most 投影仪s can’t project a pure black and don’t actually go from 0 lux to full white in a pitch black room. (顺便说一句,Medium渲染0和小写O是一样的……奇怪……o0o0o0o0). 简而言之,亮度的测量是复杂的,威尼斯人电子游戏正在极大地简化它.

在室内

好了,先不说这个了. 如果是1,000流明视频投影仪覆盖一平方米的表面积(不是很大的表面), 假设黑色是0勒克斯最亮的白色是1000勒克斯. 这给了威尼斯人电子游戏一个好的 对比度 在黑暗的房间里显示黑白之间的所有颜色. 现在, lets turn the lights on in this room and pretend we just bumped up the ambient lighting in the room to 250lux. 现在 our black level on our surface area is starting at 250lux and our white is still at 1000 lux — our contrast has gone down and the image is starting to look pretty washed out. 咱们把房间的窗户打开,把亮度调到1000勒克斯. 现在 the wall surface is as bright as our 投影仪 can go and there really is no space for a black level — our projected image, 即使它是纯白色的雪——可能在这一点上根本看不见.

对比问题

在阴凉处

让威尼斯人电子游戏到外面的阴凉处去今天那里的亮度是10000勒克斯. 这意味着要得到威尼斯人电子游戏之前0 - 1000勒克斯的对比度, 威尼斯人电子游戏必须从11开始,000流明投影仪投射一平方米. Our black is the 10,000 lux surface and our white is the brightest spot of our 11,000 lux projection. 感知, 对威尼斯人电子游戏的眼睛, this sense of contrast gets a little difficult to explain because of all the optical and chemical changes going on for our eyes to adjust and perceive these different brightness levels. A 10,在黑暗的房间里,在100万平方米的表面上,000 lm投影仪可能比1有更好的对比度,000 lm投影仪在相同的表面积上, 但你的眼睛可能很难分辨出其中的区别. 或者是10000勒克斯的白色图像那么小看起来可能会很痛苦或不舒服.

完整的日光

如果你还在跟着-让威尼斯人电子游戏把镜头移到白天. 威尼斯人电子游戏在沙漠中有一个一平方米的投影屏幕,在100度是一个阳光充足的日子,000勒克司的光线来自太阳. 即使是用投影仪在一平米上达到这样的亮度,威尼斯人电子游戏也需要 100000流明 投影仪.

不幸的是,这些都不存在. 😨

的 最亮投影仪的世界纪录 是43000流明. 它消耗7kW的电力. 一个更标准的20000流明投影仪消耗大约3kw,看起来像这样:

Barco FLM20坐在公路上

"你不能把2到3个加起来吗?“不幸的是,添加光并不是这样工作的. Just because there are double the lumens coming from these 投影仪s doesn’t mean it is perceptually twice as bright. This is because of something I mentioned earlier where 投影仪s typically don’t project zero lux as black, 尤其是那些明亮的. 所以叠加两个投影仪并投射黑色将会进一步提高黑色的亮度, 伤害你的对比. 堆叠2个5000米的投影仪,你得到的大概是7500米,而不是10000米.

We 可以 得到100,000勒克斯的亮度和标准的20,000流明投影机, 但只在很小的表面积上,只有0.20平方米或20 x 20厘米. 不是电影院那么大的屏幕.

如果威尼斯人电子游戏想在10万勒克斯的日光下,用投影覆盖普通大小的影院屏幕,该怎么办. 假设一个10m x 10m的投影面或~33ft x 33ft. 为了匹配100,在这种尺寸的屏幕上, 威尼斯人电子游戏需要一台能够投影的投影仪 100万流明 的亮度. 威尼斯人电子游戏需要在上面再加50-100%才能给威尼斯人电子游戏一个适当的黑白对比. 这是标准的20,000流明投影机s we are only at about 1–2% of the brightness we would need to cover an appropriate screen. 即使威尼斯人电子游戏回到真实屏幕的16:9长宽比, that only cuts down our surface area to a little more than half of a 10m x 10m surface and brings us into the 500,000–750,000流明. A 20,000流明投影机 is typically plenty bright in a normal movie theater where a 30ft wide screen might be getting around 400lux for its surface.

As far as power consumption and heat — We’ll just (inaccurately) follow a linear increase for lumens and wattage (20k lumens was about 3500W, 43k流明约为7000W)——这意味着为威尼斯人电子游戏的100万流明投影机提供动力, 威尼斯人电子游戏需要大约 175000W 的权力. All dependent on the type of materials used to generate that light — like LED’s using less power than incandescent — although most 投影仪s in the bright end use xenon bulbs. 我不知道该用什么方法来计算这么亮的东西的潜在散热, 但它是 可能 明亮和热到足以熔化大多数材料,甚至可以产生, 在一个小的表面区域容纳和引导那么多的光.

有超亮手电筒的视频,它们的流明确实非常大(这里有一个声称90000流明), but 投影仪s have to pass through a lot more optics just to actually generate their image and this costs significant brightness. 例如,从DLP投影仪上移除色轮可以使亮度增加两倍或三倍.

的re are things that can be done to improve the surface itself for projection so that it doesn’t absorb as much sunlight. Some of these screens are things like silver screens that reflect light coming from front on much better than light coming from above. Gray screens can help a bit as they reduce the absorption of ambient light — especially if combined with rear projection and as much shade as possible over the front.

那LED墙呢?

布鲁克林的巴克利中心和他们巨大的户外LED墙

所以……在日光下在室外投影——可能短期内是不可能的. 那LED视频墙呢? Those are visible in Times Square during any point of the day in full light and they are just a bunch of tiny LEDs. 然而, a projection surface is designed to reflect full spectrum light — which reflects the 投影仪 and all this ambient light. LED panels don’t have this problem — they are black and designed to absorb ambient light and emit their own bright light. This means the contrast needed to perceive a nice image doesn’t need to be anywhere near the level of projection.

正如前面所讨论的,像LED壁是用尼特而不是流明来测量的.

nit更多的是一个表面区域的发射,而不是仅仅反射其他的光. 这种转变(比我聪明得多的人已经发现)是:

1 Nit = 3.426流明

iPhone屏幕的最大亮度约为600 - 700nit. 户外LED瓷砖每平方英尺的亮度令人难以置信 这些巴瓦 是5000尼特,还是相当于每平方英尺17000流明. 室外阳光直射时建议使用5000尼特以上. But this isn’t even getting to the brightness of the actual LED die itself — the tiny point of the LED that actually emits the light. 发光二极管在其微小的表面积上可能有接近10万个虱子. 所以在威尼斯人电子游戏看来,它比黑色LED面板的其他部分要亮得多. 如果你分解一个LED面板的表面区域, 也许只有4%是真正的光点,96%只是用来吸收阳光的黑暗. 这使得感知亮度比仅仅投射和反射的阳光要高很多.

总结

You can’t project a light sucking black anti-photons and you can’t project and compete with the sun — stick with LED walls if you’re outside.

也有 专业 LCD monitors made specifically for the purpose of outdoor usage — they also come with the bonus of being weatherproof and are a better choice for a wide range of temperatures and environments.

引用其他阅读:

测量光与感知光

傻瓜和流明

尼特对流明- proAV

傻瓜和勒克斯

坎德拉,卢蒙,勒克斯:方程式

理解和解释lux值

据说手电筒比太阳还亮

流明和勒克斯在图像中解释

XKCD:如果地球上的每个人都用激光笔指向月球,它会变色吗?

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