Digital camera tutorials and digital photography course - DCVIEWS

Digital camera tutorials and digital photography course - DCVIEWS: "Blooming effect
Image distortion - Blooming effect - Digital cameras, digital camera reviews, photography views and news tutorials

Photo by Andreas BusseWhen light passes the lens of a digital camera and is captured by the CCD it is converted into an electrical charge.
There is a limit to how much charge each pixel or photosite can store. If there is too much charge for one photosite it will overflow to its neighbouring pixel causing an effect which is called blooming or streaking. Manufacturers try to eliminate this effect by “anti-blooming gates” which can be compared to vertical drainage channels running beside each row of photosites. These allow the overflowing charge to flow away without affecting surrounding pixels.

Though these anti-blooming gates are fairly successful at avoiding the problem, very extreme exposure situations can still lead to blooming. Especially where a very bright edge is next to a very dark edge, as seen with leaves or branches of a tree shot against a bright sky. It will be visible as a white halo or vertical streak which extends for several pixels. The effects of blooming often make chromatic aberrations more visible. These are the purple lines along dark edges in an image, caused by the effect of blue light bending more than red light."

铱星计划-Story of Iridium satellite phone

I found this story very interesting. The idea of Iridium satellite constellation is fascinating even now when I already know it was a commercial failure. The story is thought-provoking and a good lesson for all high-tech product companies. However, in a technical term, the dream of connecting people over any obstacles on the ground using a satellite network is amazing. I would be very interesting to see where ISC phone will go and if it can turn out to be a commercial success in the future.

铱星计划是一个让许多摩托罗拉人兴奋不已的想法。
　　　　　　革命性的想法从何而来？对于摩托罗拉的工程师巴里•伯蒂格来说，它来自于妻子在加勒 比海度假时的抱怨，说她无法用手机联系到她的客户。回到家以后，巴里和摩托罗拉在亚利桑那州工作的卫星通信小组的另外两名工程师想到了一种铱星解决方案 ——由77颗近地卫星组成的星群，让用户从世界上任何地方都可以打电话。由于金属元素铱有 77 个电子，这项计划就被称为了铱星计划，虽然后来卫星的总数降到了 66 个。
　　　　
　　　　　　这是个好的创意吗？尽管遭到伯蒂格顶头 上司的否决，这一计划却得到了摩托罗拉总裁罗伯特•高尔文的青睐并给予了支持。对于罗伯特，以及他的儿子克里斯 •高尔文（后来成为他的继任人）来说，铱星计划是摩托罗拉技术高超的显示，具有巨大潜力，令人振奋，决不可放弃。对于摩托罗拉的工程师们来说，建立铱星群 的挑战是一次经典的“技术拉锯战”——50多亿美元的代价终于让他们在1998年将铱星首次投入使用。
　　　　这是一个非常宏伟而超前的计划，它 最大的技术特点是通过卫星与卫星之间的传输来实现全球通信，相当于把地面蜂窝移动系统搬到了天上。从技术讲，铱星系统是相当了不起的，它采用星际链路。在 极地，66 颗卫星要汇成一个点，又要避免碰撞，难度很高。从管理上讲，它又是一个完整的独立网，呼叫、计费等管理是独立于各个国家通信网的。（这种独立计费再后来给 它的运营带来很大麻烦。）低轨道卫星与目前使用的同步轨道卫星通信系统比较有两大优势：首先，因为轨道低，只有几百公里，信息损耗小，这样才可能实现手机 到卫星的直接通信。我们现在的任何手机都不可能和三万公里以外的同步卫星直接通信；第二，由于不需要专门的地面基站，可以在地球上任何地点进行通信。 1991 年摩托罗拉公司联合了好几家投资公司，正式启动了“铱星计划”。1996 年 ，第一颗铱星上天；
　　　　　　1998年11月1日， 在进行了耗资1.8亿美元的广告宣传之后铱星公司展开了它的通信卫星电话服务。开幕式上，副总统阿尔•戈尔用铱星打了第一通电话。电话机的价格是每部 3，000美元，每分钟话费3-8美元。结果却令人不无沮丧。到1999年4月，公司还只有1万个用户。面对着微乎其微的收入和每月四千万美元的贷款利 息，公司陷入了巨大的压力之中。4月里，就在公司宣布其季度财务报告的前两天，首席执行官斯坦阿诺辞职，宣称他与董事会在战略问题上发生了分歧。公司内部 一位资深人员约翰•理查德森迅速接替斯坦阿诺成为临时首席执行官，但毁灭的阴影却已经笼罩了上来。
　　　　
　　　　　　1999年6月，铱星解雇了15％的员工，甚至包括几位参与了公司营销战略规划的经理。8月，它的用户只上升到2万个，离贷款合同要求的5万2千个相去甚远。1999年8月13日，星期五，在拖欠了15亿美元贷款的两天之后，铱星提出了破产保护的申请。
　　　　半年后的 2000 年 3 月 18 日，铱星公司正式破产。铱星成了美丽的流星。66 颗卫星在天上自己飞了几年，终于于 2001 年被一家私募基金公司（Private Equity）以两千五百万美元的低价买下。
　 　　　铱星计划是通信史上一个流星，一个美丽的故事（A Beautiful Story）。摩托罗拉公司很聪明地利用其技术优势吸引了全世界的眼球。该计划一出炉就引起世人的广泛注目，也赢得了风险投资家的青睐。摩托罗拉为此自己 拿出了十亿美元，同时钓鱼似的从投资公司有拿到近五十亿美元，从而大大降低了自己的风险。但是，在商业运作上，摩托罗拉做得很不成功。首先，市场分析现在 看来就有问题，成本过高导致用户数量不可能达到预计的盈利所必需的规模。而成本过高的原因又是技术选择的失误造成的。摩托罗拉长期以来都是一个了不起的技 术公司，它长于技术，但是过分相信技术的作用。铱星计划在技术上是无与伦比的，但是，过于超前市场的技术不仅导致成本过高，而且维护费用也是巨大的。另 外，引入风投本身的弊端在项目的后期凸显出来，那就是投资者为了收回投资，过早将铱星系统投入商用，当时这个系统通话的可靠性和清晰度很差，数据传输速率 也仅有 2.4Kps ，因此除了打电话没法做任何事，这使得潜在的用户大失所望。概况来讲，就是铱星计划太超前了，它开业的前两个季度，在全球只有一万个用户，而当初市场的分 析去乐观地预计，仅在中国就能有这个数的十倍。在后期商业运作上。铱星公司问题很多，最终导致银行停止贷款、部分股东撤回投资，并导致公司在股市上停盘的 致命打击。
　　　　现在，仍然可以买到铱星手机。在淘宝搜索“铱星”，能找到不少卖家价钱在1万到1万6之间。据说，这类手机在国内也还比较畅销，针对于特定野外探险的人群进行销售。这种几乎成了奢侈品，像我们这等普通大众，是无福消受了。

What is the temperature in space?

If you are too lazy to read this post, I will give you a quick answer. It is 3 kelvin or -270 degree if you prefer calcius. If you want to know more, come to read this.

This is an interesting question, because if there is no molecules, there is no indicate to termperature. However, the truth is there is still particles in the space though very few. The temperture in space should be better refered as the temperture of an object if we place it in an empty space. I found an interesting article about it. I am sure you will feel you are very lucky to be the citizen of the earth. Update your knowledge:
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Empty space itself cannot have a temperature, unless you mean some abstruse question about quantum vacuums.

However, if you put a physical object into space, it will reach a temperature that depends on how efficiently it absorbs and emits radiation and on what heating sources are nearby. For example, an object that both absorbs and emits perfectly, put at the Earth's distance from the Sun, will reach a temperature of about 280 K or 7 C. If it is shielded from the Sun but exposed to interplanetary and interstellar radiation, it reaches about 5 K. If it were far from all stars and galaxies, it would come into equilibrium with the microwave background at about 2.7 K. Spacecraft (and spacewalking astronauts) often run a bit hotter than 280 K because they generate internal energy. Arranging for them to run at the desired temperature is an important aspect of design. Some people also consider the "temperature" of high energy particles like the solar wind or cosmic rays or the outer parts of the Earth's
atmosphere. These particles are not in thermal equilibrium, so it's not correct to speak of a single temperature for them, but their energies correspond to temperatures of thousands of kelvins or higher. Generally speaking, these particles are too tenuous to affect the temperature of macroscopic objects. There simply aren't enough particles around to transfer much energy. (It's the same on the
ground. There are cosmic rays going through your body all the time, but there aren't enough to keep you warm if the air is cold. The air at the Earth's surface is dense enough to transfer plenty of heat to or from your body.)