[交流] Nikon D200 個人使用觀感

garychang

關於白平衡，曾發文於友站Mobile01，今轉貼於下:
另外我蠻認同82544的，當然自動白平衡會有它的挑戰及問題，不過如果自動白平衡更聰明
或更正確，我想沒有人會反對或抗議吧?
順道一提，個人認為nikon既然放了機上的light sensor，firmware工程師其實就應該要好好的善用啊。
=======================
定義顏色，我們常用的是色座標
定義白色，我們常用的是色溫。
以Canon而言，其"白色"的色溫是5200k的。以下取自
http://www.dpreview.com/learn/?/ ... hite_Balance_01.htm
簡譯及原文並陳於下

White Balance // 白平衡
By Vincent Bockaert //  文生 波卡特 原著
大蟲簡譯

色溫
絕大多數的光源並非100%的純白，但是卻擁有著十分可靠以度K表示的色溫。舉例來說，中午的陽光比起偏黃的早晨或傍晚的陽光是十分接近白色的。下面這個圖表給大家一個大致上的陽光色溫值。
<font color="#F5F5DC">Color Temperature
Most light sources are not 100% pure white but have a certain "color temperature", expressed in Kelvin. For instance, the midday sunlight will be much closer to white than the more yellow early morning or late afternoon sunlight. This diagram gives rough averages of some typical light sources.</font>

Type of Light//光源        Color Temperature in K(色溫°K)
Candle Flame         燭光
1,500
Incandescent         燈泡
3,000
Sunrise, Sunset  日出/傍晚
3,500
Midday Sun, Flash  中午 (譯註:FLASH可能是指閃光燈或閃電，不確定)
5,500
Bright Sun, Clear Sky         明亮的日光
6,000
Cloudy Sky, Shade 多雲
7,000
Blue Sky  萬里無雲
9,000

白平衡
正常情形下，我們的眼睛會去補償各個光源下的不同色溫。數位相機需要尋找一個參考點來重現白色。它將會基礎於此參考點重新計算其它顏色。舉例來說，鹵素燈照射於一面白牆，則牆上會投射出黃色--事實上這面牆原本應該是白色的。所以如果相機知道這面牆本來是白的，它將會補償出所有的其它場景內的其它相應的顏色。

多數的數位相機都擁有自動白平衡的功能， 也就是相機會全面檢視整個圖片的顏色並且會計算出最適合的白平衡。然而這些系統(譯注:自動白平衡)有時會被愚弄尤是是在單一顏色為主的場合，例如綠草，或是以下(請至上述連結原始網站)這一類場景中沒有"自然白色"的例子。

譯注:網站上有兩張範例圖片，場景非常類似，然而一張是藍天+山石，一張是藍天白雲+山石，因為有無白雲做自動白平衡的基準，所以兩張的照片的效果就前輩不同。

多數的數位相機也予許您手動選擇白平衡，大致上有日光、多雲、螢光、白炙燈等，半專業級或數位單眼予許您定義白平衡的參考點。當你在實際的拍照前，您可以先聚焦於場景中應該是白色或是自然的灰色，或是白卡或灰卡，之後當真正拍照時相機將會以此做參考。

譯注:謝謝收看，歡迎討論
<font color="#F5F5DC">
White Balance

Normally our eyes compensate for lighting conditions with different color temperatures. A digital camera needs to find a reference point which represents white. It will then calculate all the other colors based on this white point. For instance, if a halogen light illuminates a white wall, the wall will have a yellow cast, while in fact it should be white. So if the camera knows the wall is supposed to be white, it will then compensate all the other colors in the scene accordingly.


Most digital cameras feature automatic white balance whereby the camera looks at the overall color of the image and calculates the best-fit white balance. However these systems are often fooled especially if the scene is dominated by one color, say green, or if there is no natural white present in the scene as show in this example.

//圖說不翻
The auto white balance was unable to find a white reference, resulting in dull and artificial colors.
       
The auto white balance got it right this time in a very similar scene because it could use the clouds as its white reference.圖說結束//

Most digital cameras also allow you to choose a white balance manually, typically sunlight, cloudy, fluorescent, incandescent etc. Prosumer and SLR digital cameras allow you to define your own white balance reference. Before making the actual shot, you can focus at an area in the scene which should be white or neutral gray, or at a white or gray target card. The camera will then use this reference when making the actual shot. </font>