氣象攝影心得

Homan · 發表於 17-2-2009 18:46:24

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文章是以以下英文為基礎的，仍然改進中，有意見請加上。

Royal Meteorological Society 
Photographing the weather  
Here are some tips on how to successfully photograph the weather.  
Cameras, lenses and film  
In general any camera, old or modern, digital or film, is capable of recording an acceptable weather picture. A relatively poor image of a rare phenomenon or event taken with a cheap disposable camera is better than no picture at all, but obviously the better (and arguably the more expensive) the camera that you use, the better quality pictures you are likely to achieve. More expensive cameras will tend to have the better quality lenses and offer the greater functionality in their exposure and other systems.     
相對而言，昂貴的數碼相機在像素大小，以及某些系統性方面的表現會比較出色。
近一兩年，中，小型數碼相機無論在電源，鏡頭，影像處理上已經逐漸成熟。
最關鍵的是，還是身邊經常帶備一部，就算只是簡單輕便的相機。
至於籌備一次專題攝影，配備多一兩支鏡頭，三腳架，後備電池都是基本要求。  
The best cameras to use for weather photography are those which offer good versatility. For example, the ability to manually overide automatic exposure systems can be useful in certain illumination conditions. 'Spot metering' for determining exposure can be extremely useful. The ability of your camera to zoom the focal length of its lens from telephoto to wide-angle is also a powerful tool. A good Compact camera will have a zoom lens but there is no doubt that a Single Lens Reflex (SLR) will offer the best quality in this respect as SLRs allow you to interchange lenses.   
型號選擇方面，鏡頭最好具備一定廣角程度 ，要應付一般的氣象攝影 28-120mm 已經相當足夠。 
雖然對於有經驗的攝影者，有時候亦會依賴自動模式拍攝， 作爲主要參考；但是由於實際上會遇到不同拍攝環境， 即使是初學者，購買相機最好附有一定程度上手動模式。      
即使是
Being able, as with an SLR, to fit a filter (such as a polarising filter) to the front of the camera lens is indispensible. Lens flare can be a problem when photographing the sky with the sun in the frame or just outside, so the ability to fit a lens hood to the lens will help to reduce flare from the sun.  
（ 遮光罩有必要提及嗎 ？）  
If you buy a digital camera, as opposed to a camera using film, then I would suggest that you choose a camera with a sensor that will offer the greatest resolution. A 10 megapixel camera is ideal, a 6 megapixel camera will be okay, but sensors with less resulution will give picture quality far less than that available by using film. This is not a problem if you just want some prints for personal use, but if your intention is to submit your photos for publication then it may be an issue. The big advantage of digital, over film, is the fact that the pictures are available immediately. You can spot any problems and correct them straight away. Also the pictures are available in digital form for publication, or for manipulation on the computer, without going through the intermediate process of scanning negatives, prints or slides.      
像素大小方面，普通數碼相機提供的六百萬或以上已經足夠應付一般的商業出版印刷， 當然，專業一點的數碼相機可以輸出原格式，方便用家在電腦處理影像。   
If you do use a film camera then for most weather photography you should use slow or medium speed film - i.e. films with an ISO rating of 100 or 200. There may be occasions under dull lighting when you need a 400 ISO film but this will give grainier pictures. The slower speed films offer the finest resolution and colour saturation. In effect the same applies with digital cameras. Set your digital camera to as slow a speed as appropriate to the lighting conditions. Higher speed settings introduce 'noise' on the digital file, having much the same effect as the graininess of high speed films.    
無論是傳統或者是數碼相機拍攝，設定合適的感光速度 (ISO) 是非常關鍵的。 例如，烏雲密布的日子，光源減低，即使在戶外，在合理的快門速度限制下，拍攝天空的雲要達到有層次感，相機須要調較至ISO 200 ， 甚至ISO 400 。 同樣，拍攝日出，日落，以及惡劣天氣，應該主動使用稍為高一點感光度，或使用三腳架輔助。  
With film cameras, the choice of whether to use negative film for prints, or transparency film for slides, to some extent depends on the eventual use of your pictures. If intended for publication (for example in Weather) then transparencies are better than prints. If your pictures are only for personal interest then prints might be more convenient. The main thing to note is that with transparency film the slides that you expose in the camera are the final products. With negative film you will rely on the processing company to produce the final print and it is a fact that automatic printing machines tend to average out the exposure of the scene. This means that no matter how careful you've been to select the correct exposure for clouds when you take the picture, they may appear washed out and pale in the final print. For this reason then, slides give the better quality. Slides also give more colour saturation, but beware, transparency film has far less exposure latitude than negative film and so your exposure needs to be more precise when using slide film.
Filters  
（菲林拍攝細節， 我建議可以省掉 ）  
Assuming your camera allows you to put a filter onto the front of the lens, then there are principally two filters which are most useful - a polarising filter and a graduated neutral-density. A skylight filter is also worthwhile.  
（polarising filter  你有經常用嗎？應該怎樣翻譯，偏光鏡？）  
A skylight filter fitted to the lens all the time is a good idea as it will protect the surface of your expensive camera lens from dust and scratches, It's main aim though is to cut through haze to give a slightly clearer image. In mountains, because of increased ultra-violet rays at altitude (giving a slightly blue colour cast), you may wish to put a UV (ultra-violet) filter on the lens instead. It effectively does the same as the skylight but with a more powerful effect.  
（這方面你有心得的話，請提供。）  
A polarising filter is absolutely indispensible when photographing clouds. It allows you to increase the contrast between the white clouds and the background blue sky. Polarisation of the blue sky is at a maximum 90 degrees from the sun. Near to the sun though, where polarisation of the light is less, the filter will be ineffective. Modern cameras with automatic exposure and focus will require a circular polarising filter. With simple cameras which do not have a screw facility to mount filters it is often possible with a little practice to simply hold the filter in front of the lens.  
（偏光鏡， 這方面你有心得的話，請提供。）  
In pictures where you include both sky and foreground, the sky may be much brighter than the foreground. Confronted by such a situation, if you expose for the sky your camera's exposure meter will suggest settings that will automatically underexpose the foreground and turn it into a silhouette. At the other extreme if you select the exposure for the foreground the sky will lose colour and become washed out with overexposure. A meter reading from a bright mid-tone gives the best result with a better balance of foreground detail and colour in the sky. The advantage of the graduated neutral-density filter (which has half the filter clear and half the filter darkened, is that you can place the dark portion over the sky to reduce its brightness.   
有時候，光源充足的環境下，往往出現天空主體跟地面背景有強烈光度反差。 。。。。。。？？？？？     
Some general tips for good weather photography  
1) It is usually worthwhile including some foreground when photographing clouds to provide a sense of scale and orientation. Your picture will be enhanced if the foreground is interesting and well composed. Make sure the horizon is level - the act of pressing the shutter button can sometimes cause people to tilt the camera slightly and result in a wonky horizon. Don't always stick to horizontal format; remember, sometimes, it may be appropriate to turn the camera on it's side and shoot a vertical format picture (e.g for the front cover of Weather).   
2) Expose the film or digital picture correctly. Slight underexposure of clouds is better than overexposure which will result in detail being washed out. Use 'spot metering' on your camera if available. Use a graduated neutral-density filter, if necessary, to decrease the brightness of the sky with respect to the foreground. It's a very good idea to bracket exposures, that is to take one picture at what you think is the correct exposure and also take further pictures, one slightly overexposed and one slightly underexposed. At least one of the 3 shots should be correctly exposed. With film this technique will obviously increase the cost of your photography as you'll take at least 3 pictures of the scene rather than just one, but with digital cameras you can quite happily take lots of photos with no cost implications.     
拍攝晴朗無雲的天氣，天空部分很容易曝光過度。
拍攝陽光的照射中，霧，灰霾， 因爲散射，需要把測光系統的提供指示再 減低 1/3，2/3 級；
相反，。。。。。。。  
並且使用包圍曝光，也就是說，分別使用較爲高 1/2，及較爲低 1/2級多拍攝各一張。  
3) Use a polarising filter to enhance colour saturation and contrast between blue sky and white cloud.   
4) In dull lighting conditions a tripod will be indispensible. With subjects taken at night (such as lightning), or in twilight conditions (such as noctilucent cloud), a tripod is absolutely essential. For pictures of noctilucent clouds you will need to take a time exposure of a few seconds using the B (bulb) shutter speed setting. Take lots of pictures to bracket the exposures.   
前面提過。  
5) Lightning photography is relatively simple; all you need is a tripod, a camera loaded with slow film, say 100 ISO, or your digital camera set to this, and set the lens aperture to one of the smallest f/numbers - i.e. a wide aperture. Point the camera towards where the lightning is occurring and open the shutter using the B (bulb) shutter setting for several seconds to a minute. Close the shutter after you see a llightning stroke in the field of view. Beware, if you leave the shutter open too long the background sky will become overexposed. You will need to be prepared to take lots of pictures, some of which will be wasted. It is best if the storm is some considerable distance away, rather than nearby.  
Quite apart from not wanting to get the camera wet with rain, your safety must be the number one priority when you are near a thunderstorm. Your tripod can make an excellent lightning conductor! Nowhere near an electrical storm can be totally safe, but shooting from inside a building through an open window is far safer than being outside in an open space. Photographing a storm from a distance you can use your camera's zoom or telephoto lens to frame the picture without putting yourself in danger.  
安全第一。確保自己身處在無潛在風險的位置，再考慮開始拍攝。
閃電距離有兩公里以上 ，光圈可以設定在 5.6 或更大；
閃電距離有兩公里以内，光圈可以設定在 8 或更小，否則可能曝光過度。  
6) When photographing halos and other phenomena near the sun you can exclude the very bright sun from the picture by hiding it behind objects such as trees or buildings.  
 George Anderson
Photo Editor, Weather

alexphoto · 發表於 18-2-2009 11:55:08

本人認為氣象攝確實是需要一定的技術, 但最重耍的是你能否掌握準確的天氣變化資料, 香港屬亞熱帶氣候, 夏天的天氣變化很大, 底氣壓所帶來的兩區固然是有跡可尋, 但有時白天的高溫也可為晚間帶來雷兩, 這些突如其來的天氣現象很難預測, 令拍攝者無法作好準備。另外, 你必須能隨時候命, 一掌握到天氣的狀況就能立即出簽發,這點看來只有全職氣象家才有條件做到, 幸好香港天文台的先進天氣監察系統及其高透明度的工作模式令我們就算身處不見天日的家中,只要透過天文台的網頁也能清楚了解當前及未來一段時間的天氣變化, 在網頁中的天氣雷達就正正是個好幫手, 但我們也要懂得如何觀看及把它提供的數據應用到天氣預測之中。有見及此, 天文台特意為市民舉辦了一個"天氣雷達及衛星圖像基礎課程", 有興趣的朋友可到以下網址看看。
<A href="http://www.hko.gov.hk/education/edu03course/course/coursec_0902.htm">http://www.hko.gov.hk/education/edu03course/course/coursec_0902.htm</A> (已截止報名, 唯有等下次)
小弟對氣象認識不多, 有的也是從天文台的網頁中學到, 但我對大自然的奧妙是感興趣的, 縱使我的學識不多, 所以希望能在這裏跟大家互相學習交流。

[ 本帖最後由 alexphoto 於 2009-2-18 18:07 編輯 ]

c_Foo · 發表於 18-2-2009 12:51:25

夏天又到，又係時候帶定相機出門口隨時候命 ~~

alexphoto · 發表於 18-2-2009 18:01:51

冇錯, 上次買咗個相機兩褸都未用過, 仲係個friend 度執咗頭盔, 呢套裝備應該可抵擋9號風球,
但我地架衝鋒車................唔知Homan有冇考慮換架Landrover或"駻馬"

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