TP-Link 703n, OpenWrt, Cisco VPN, CHNROUTES
前段日子在@weeker的怂恿下购置了TP-Link 703N,100软妹币有找。买这么个烂牌子的小东西回来当然是用来折腾的,以下便是折腾内容:
先来看看703N的硬件参数:
- Atheros AR7240 CPU (400Mhz)
- Atheros AR9331 Chipset (integrated wireless)
- 802.11 b/g/n 150Mbps (130Mbps real)
- wireless power output 20dBm – 100mW
- 4 MB flash memory
- 32 MB RAM
- USB 2.0 port
- Powered via micro-USB socket
- Tiny form factor: 5.7cm x 5.7cm
Can you share this?
我希望这封信有更多人能看见,所以不转发,直接在这里贴出。
Jimmy Wales
Thu, Dec 29, 2011 at 9:05 AM
Reply-To: Jimmy Wales
To: kDolphin
Dear kDolphin,Here’s how the Wikipedia fundraiser works: Every year we raise just the funds that we need, and then we stop.
Because you and so many other Wikipedia readers donated over the past weeks, we are very close to raising our goal for this year by December 31 — but we’re not quite there yet.
You’ve already done your part this year. Thank you so much. But you can help us again by forwarding this email to a friend who you know relies on Wikipedia and asking that person to help us reach our goal today by clicking here and making a donation.
If everyone reading this email forwarded it to just one friend, we think that would be enough to let us end the fundraiser today.
Of course, we wouldn’t turn you down if you wanted to make a second donation..
Google might have close to a million servers. Yahoo has something like 13,000 staff. We have 679 servers and 95 staff.
Wikipedia is the #5 site on the web and serves 470 million different people every month – with billions of page views.
Commerce is fine. Advertising is not evil. But it doesn’t belong here. Not in Wikipedia. Wikipedia is something special. It is like a library or a public park. It is like a temple for the mind. It is a place we can all go to think, to learn, to share our knowledge with others.
When I founded Wikipedia, I could have made it into a for-profit company with advertising, but I decided to do something different. We’ve worked hard over the years to keep it lean and tight. We fulfill our mission, and leave waste to others.
Thanks,
Jimmy Wales
Wikipedia FounderYou are receiving this email as a valued donor of the Wikimedia Foundation. If you do not wish to receive any future emails from the Wikimedia Foundation, unsubscribe instantly.
Wikimedia Foundation, Inc.
P.O. Box 98204
Washington, DC 20090-8204
United States of America
为什么说50mm镜头在APS-C幅面上是人像头
50mm镜头在135胶片机上被称作“标头”,因为它的视角最接近人类的双眼视角。当它被使用在现在常见的APS-C幅面的DSLR上就变得稍稍有点复杂了。
首先,想知道什么是APS-C幅面可以先看一下这篇文章。
透视效果、透视畸变
我们一般是利用物体的相对大小来感觉远近的:距离越远,物体越小,距离越近,物体越大,这就是透视效果。透视效果有一个重要的特性就是距离越近,效果越明显。从你身前1米纵向延伸的队伍,第一名和最后一名的大小差距是很明显的;而在你100米之外的队伍第一和最后一名的大小差距就变得不那么明显。
当这个效果被应用于人像摄影时就会发生这样的情况:当被摄者距离镜头过近的话,鼻子在脸部所占的比例就会比正常情况下大,因为鼻子比脸上的其他部分更接近相机,这就是透视畸变。
要注意的是,透视畸变和镜头焦距无关,它只和被摄物体与镜头间的距离有关,在同一距离下各类焦距镜头的透视效果是相同的。
什么是人像镜头
为了避免透视畸变,摄影师需要与被摄者保持一定距离。在全幅相机上,85mm镜头让被摄者与摄影师保持足够的距离来避免透视畸变,而又不至于过远让整张脸看起来毫无立体感(因为过远透视效果不明显)。于是85mm镜头在135相机上被称作人像头。
50mm镜头在APS-C幅面上是人像头
当50mm镜头使用在APS-C机身上后,为了获得一个合适大小的人像我们需要距离被摄者相比全幅机身更远。这个距离很好算,对于 Canon来说是50mm x 1.6 = 80mm;对于Nikon来说是50mm x 1.5 = 75mm。也就是说使用APS-C机身与50mm镜头拍摄人像时,为了得到较好的效果摄影师与被摄者之间的距离和全幅机身上使用80mm镜头是相等的。
一些其他的争论
上面这些字应该说清楚为什么50mm镜头对于APS-C机身来说是人像镜头了吧?不过曾有人和我扯什么50mm有明显的焦外二线性成像问题,可问题那个是镜头本身的质素问题,和焦距并没有什么直接联系。
注:以上镜头所指都是135全幅镜头
宽容度的实际意义
《宽容度》中谈到了宽容度对于摄影来说的实际意义:一个安全曝光的区间,这里接下去说一下实际使用会遇到的问题。
宽容度并不平均
底片(或者DC的CCD/CMOS)的宽容度并不是平均的,2档的宽容度并不意味着阴影区(最暗)和强光区(最亮)是各1档,事实上阴影区的宽容度都在0.5档左右(宽容度最大的黑白胶片是2档)。
高反差度和低反差度
“大于7档光圈的是高反差度场景”(引自《纽摄》),就是说被摄画面的阴影区和强光区之间的亮度跨度超过7档光圈(大约是128倍),对于胶片来说是这句话是对的,但对于CCD/CMOS来说这个数值会稍小些。
主体是什么
由于不可能记录高反差度场景中所有的亮度变化,所以拍摄前就应该明确将要拍摄影像的主体是什么。
不要过于依赖灰卡
在高反差场景下灰卡提供的数值对于底片(CCD/CMOS)来说是做不到的,灰卡只有在被摄场景的宽容度接近器材的宽容度才会有用。