Fafner's 遁世居

Thom Hogan 是 Nikon 相機界有名的評論者兼作者，他的教學電子書頗受好評，而且他的器材評論，也被認為是非常專業及中肯的。他的網站，很值得 Nikon 用家常去逛逛。

網址：http://www.bythom.com/

我最近才開始研究閃燈，而Thom Hogan網站上，有個「閃燈Q&A」，把一些他在教授閃燈技巧時，學生們常問的問題和解答列出來，裡面有許多東西，我的程度還不足以去了解，而有一部分關於操作和補光設定的，我覺得還蠻實用的，特別挑出來翻譯，便於日後查閱。

Q: Does using slow sync open me up to getting blurred images?
Answer: Yes and no. When you shoot with flash, there are two exposures going on: the flash exposure on the subject and the background exposure. If flash is the main source of light, a stationary subject lit by it should always be sharp, as the slowest Nikon flash duration is about 1/830 of a second. The background, however, very well may go soft or get blurred by poor handholding technique or subject movement. Many photographers have learned to use this to their advantage--there's one style of flash that uses very long shutter speeds and panning/zooming/tilting to purposefully blur the background yet still use the flash to "freeze" the subject.

問：使用慢速同步閃燈會使我拍出模糊的影像嗎？

答：可說會，也可說不會。當用閃燈拍攝時，有兩種曝光同時進行著：主體的閃燈曝光和背景曝光。如果閃燈是主要光源，其所照射的靜態主體會很銳利，因為最慢的 Nikon 閃燈，閃光持續的時間大約也只有 1/831 秒。而背景，很可能因手持技巧不佳或物體的移動，使得成像偏軟且變得模糊。許多攝影師會善用此種現象來拍攝相片——有一種打閃燈的方式，是使用「極慢」的快門，然後平移/變焦/轉動相機，故意讓背景變得模糊，並以閃燈來「凍結」拍攝主體。

Q: What's the simplest method to set fill?

Answer: Here's what I teach students as a base in my workshops (you can get more elaborate, but this addresses the main issues you face with fill flash on Nikon bodies):

1. Camera set to Aperture-preferred exposure mode. Gets rid of aperture limitations in Program mode.
2. Camera set to Slow Sync or Rear Sync. Gets rid of the bottom end shutter speed limitation at 1/60.
3. Flash set to Standard TTL (press Mode button on flash until only TTL shows on flash LCD). Gets rid of camera-induced flash compensation level, which is unknown.
4. Flash set to the fill level you want via flash exposure compensation, typically -1.0 stop for people, or Galen Rowell's "magic" -1.7 value for outdoor scenic fill. Allows you to control the fill level rather than the camera.

問：最簡單的補光設定法是？

答：以下是我在教學生時的基本要點（是可以講得更詳細點，但這是在使用 Nikon 相機作閃燈補光時，所會遭遇到的主要課題）：

1. 相機設在光圈先決曝光模式。此為擺脫「程式曝光模式」（P mode）中的光圈限制。
2. 相機設定為慢速同步或後簾同步。此為擺脫 1/60 秒的快門下限。
3. 閃燈設在標準TTL（按下閃燈的Mode鈕，直到閃燈的LCD上只顯示著TTL）。擺脫相機感應到的未知的閃燈補償值。（譯按：我看不懂）
4. 以閃燈補償設定你所要的閃燈補光程度，一般來說，拍人-1.0，或是 Galen Rowell 所謂「神奇」的戶外場景補光值 -1.7。此為讓你來控制補光程度，而不是交由相機。

Q: Isn't -1.7 stops of flash compensation a bit extreme?

Answer: Most nature and scenic professionals use -1.3 to -1.7 stops for their fill flash setting because they are trying to do one thing only: increase shadow detail (an alternate way of saying this: decrease overall scene contrast). Why? Because exposures for slide film need to be biased to the brightest object in the scene (i.e., overexposure of slide film is VERY bad). Since film has a limited dynamic range it can record with reasonable detail, if you set your exposure to put the highlight at the white point, you often lose shadow detail. The purpose of the fill flash, therefore, is to raise the film's response curve at the shadow point without further blowing out the detail. The -1.3 to -1.7 values are often just enough to pull another "stop" of useful shadow detail into an exposure without adding unduly to the highlight exposure. Films like Velvia are especially troublesome, as they have a steeper drop-off to black, and lose shadow detail faster (and this leads some to say Velvia is a high contrast film, which it's not). If you're using print film, you probably should opt the other direction: use as much flash you want, and don't worry about overexposure. That's because overexposure of a negative increases useful print densities (up to a point).

If you shoot people (weddings, events, etc.), you very well might want to use higher levels of flash, because here the primary thing you're trying to do is to get shadows off the face. My usual suggestion is to start with -1 stop and then work your way upward from there if that's not enough flash. I almost never go beyond -0.5 stops, by the way. Anything beyond that point is making the flash the primary source of light and the ambient lighting the "fill," which can look unnatural.

問：閃燈補償設 -1.7 會不會太超過？

答：多數自然或外景攝影師們，把補光時的閃燈補償設為 -1.3 到 -1.7，其唯一的目的，是為了增加暗部細節（換一種說法是：減少場景的對比）。為什麼？因為正片曝光需要注意場景中最亮部的曝光（也就是說，對正片而言，過曝是「非常」糟糕的事）。因為膠片的動態範圍有其限度，只能記錄下一定的細節，若你的曝光讓最亮部變成死白，你常會失去暗部細節。閃燈補光的目的，是拉高膠片暗部的反應曲線，而不讓細節暴掉。-1.3 到 -1.7 值，通常只會讓曝光中有效的暗部細節拉高一格，而不對最亮部再另加額外的曝光……（譯按：後面都是講底片特性，就不翻了。）

如果你拍人像（婚攝，活動等等），你可能會希望用較高的閃燈值，因為你主要的目的，是為了去除掉臉部陰影。我通常會建議從 -1.0 開始，若是覺得閃燈不足，再逐部上增。對了，我幾乎從未高過 -0.5。高過 -0.5的話，會使閃燈變成主要光源，現場光則變成「補光」，這樣看起來很不自然。