昨天吃晚饭的时候，感觉空气真干净，于是决定今天去颐和园转转。今天总体来说天气不如昨天舒服，空气质量也不如昨天，但是已经算是北京相当难得的好天气了。

　　一部分照片我上传到了web相册里了，可以到这里看。

7. Exposure Rules
The classic advice is, "Expose for the highlights, and let the shadows take care of themselves." This works with slide film and digital. But with negative film, especially color negative, you're better off overexposing by one stop.

　　对于曝光来说，经典的建议是：“对高光区正确曝光，低光区由它自己”。这个原则对反转片和数码机都适用。不过对于负片，尤其是彩色负片，最好加曝一档。

8. Quick Flash-fill Rule
When using an automatic flash unit that doesn't provide auto flash-fill ratios, set the flash's ISO dial to twice the ISO you're using. Meter the scene, select an f-stop, set the autoflash aperture to the same f-stop, and shoot. The resulting 2:1 flash-fill ratio will produce filled shadows one stop darker than the main subject.

　　使用没有自动闪光填充比率的闪光灯的时候，闪光灯的ISO设置为机身ISO的两倍。根据场景选择合适的光圈，将闪光灯的光圈设置为同样大小。这样，2:1的闪光填充比率会导致阴影区比主体光线暗一档。

9. Flash Range Rule
Want to know how much extra flash range you get by going to a faster ISO? The rule is, "Double the distance, four times the speed." For example: If your flash is good to 20 feet at ISO 100 (film or digital), it will be good to 40 feet at ISO 400.

　　增加ISO的话，闪光灯的范围能增加多少？原则是，“距离加倍，速度乘四”。例如，如果在ISO100的时候，你的闪光灯的有效距离是20英尺，那么在ISO400的时候，有效距离是40英尺。此规则适用于胶片机和数码机。

10. Megapixel Multiplier Rule
To double the resolution in a digital camera, you must increase the number of megapixels by a factor of four—not two. Why? The number of pixels in both the vertical and horizontal dimensions must be doubled to double the pixel density across the image sensor.

　　如果想把数码相机的分辨率翻倍，像素需要乘以四。原因是水平和竖直方向的像素都要翻倍。

11. Action-stopping Rules
To stop action moving across the frame that's perpendicular to the lens axis, you need shutter speeds two stops faster than action moving toward or away from you. For action moving at a 45-degree angle to the lens axis, you can use a shutter speed one stop slower. For example: If a person running toward you at moderate speed can be stopped at 1/125 sec, you'll need a shutter speed of 1/500 sec to stop the subject moving across the frame, and a shutter speed of 1/250 sec to stop him if moving obliquely with respect to the camera.

　　动态捕捉原则。捕捉垂直于镜头运动的物体，快门要比捕捉平行于镜头运动的物体快2档。捕捉与镜头轴线成45度角的物体时，快门快1挡。例如：如果一个中速跑向你的人，你需要用1/125秒快门捕捉的话；此人横穿画面，则需要1/500秒的快门捕捉。如果斜着45度角向相机跑来，则需要1/250秒的快门。

12. Sunset Rule
To get a properly exposed sunset, meter the area directly above the sun (without including the sun). If you want the scene to look like it's a half-hour later, stop down by one f-stop, or set exposure compensation to minus one.

　　拍摄夕阳的时候，要对着太阳的上方区域测光（不包括太阳）。如果你希望照出来的效果如同半小时之后的样子，可以减一档光圈，或者减少曝光补偿。

　　原文在这里。挺好看的一篇文章，学习ing。试着解释一下。

1. Sunny 16 Rule
The basic exposure for an average scene taken on a bright, sunny day is f/16 at a shutter speed equivalent to one over the ISO setting—that is, f/16 at 1/100 sec at ISO 100. From this you can interpolate, and try f/22 at the beach, f/11 on a cloudy-bright day, etc.

　　“Sunny 16 Rule”是在没有测光表的情况下，如何正确估算日光下曝光数值的方法，所以这条原则仅适用于阳光充足的情况下。将光圈设置为F/16，快门与ISO同步，或者略快。比如ISO设置为100时，快门应该设置为1/100秒（或者1/125秒）。依此类推，在海滩上应该使用F/22光圈，在多云但明朗的时候，应该用F/11光圈。

　　对于多云情况的判断，可以通过看影子的方法：

2. Moony 11, 8, and 5.6 Rules
There are many different rules that work well when shooting the moon. One favorite for a proper exposure of a full moon is f/11 at one over the ISO setting. For pictures of a half moon, use the same shutter speed at f/8, and for a quarter moon, use the same shutter speed at f/5.6.

 　　拍摄月亮的时候，很多种曝光组合都很好用。这里是一个比较常用的原则。快门与ISO同步的时候，拍摄满月用F/11光圈，弦月的时候使用F/8光圈，新月则使用F/5.6光圈。

3. Camera Shake Rule
The slowest shutter speed at which you can safely handhold a camera is one over the focal length of the lens in use. As shutter speeds get slower, camera shake is likely to result in an increasing loss of sharpness. So, if you're using a 50mm lens, shoot at 1/60 sec or faster. Not enough light? Use a flash, tripod, or brace your camera against a solid object.

　　手持相机的时候，快门的速度不应该小于镜头焦距的倒数。快门越慢，抖动越有可能造成锐度的降低。如果用50mm焦距的话，快门要达到1/60秒或者更快。如果光线实在不够的话，用闪光灯，脚架，或者把相机放到一个硬东西上。

4. Anatomical Gray Card
Metering off an 18-percent neutral gray card is a good way to get a midtone reading that will give you a good overall exposure of a scene. Forgot your gray card? Hold your open hand up so it's facing the light, take a reading off your palm, open up one stop, and shoot. (Various skin tones rarely account for even a full-stop difference.)

　　这段是说灰度板测光的，我还没这么发烧，跳过，不翻译了。

5. Depth of Field Rules
When focusing on a deep subject, focus on a point about a third of the way into the picture to maximize depth of field, because the depth-of-field zone behind that point is about twice as deep as the depth-of-field zone in front of it. This works for all apertures and focal lengths, but the smaller the aperture and the shorter the focal length, and the greater the distance you shoot at, the greater the depth of field.

　　当被摄主题比较深的时候，对焦点应选择在景深的前1/3点处，这样对焦点后的景深是前边的2倍。这个原则对于各种光圈和焦段组和都适用。不过光圈越小，焦距越短，距离被摄物体越远，景深就越大。

6. Largest Digital Print Rule
To calculate in inches the largest photo-quality print you can make with a digital camera, divide the vertical and horizontal pixel counts (see your manual) by 200. For critical applications, or if you want exhibition-quality prints, divide the pixel counts by 250.

　　想要打印出最大尺寸的照片的话，照片的尺寸（英寸）应该不大于数码图片的长宽像素各除以200。要想参加影展，或者对画质要求比较高的话，至少除以250。事实上一般来说，都是除以300的，可以列出下边这么一个表格出来。

　　这样保守算起来，10M像素的相机可以打印10寸的照片，8M像素的相机可以打印8寸的，5M像素的相机可以打印7寸的，3M想素可以打印6寸的。所以家用的话，5M其实足够了。在同样大小的CCD下，盲目追求高像素没有意义呐。