影相出來的效果

I assume you shoot digital. Noise level in digital photography is equivalent to ISO sensitivity.

In conventional photography, ISO is a measurement of film speed. The film's sensitivity to light is higher as the ISO rating goes higher. In general, film with high ISO rating is usually very grainy because of the large film grain.

In digital photography, there is no film but a sensor chip instead. Therefore, in order to increase the sensor's ability to capture more light, the camera has to increase the signal gain of the sensor. The amplified signal will also increase the level of noise. It is like, imagine you have a average CD player with built in speakers, as you increase the volume, other than the sound level is louder, you'll start hearing clipping noise. When is the clipping noise starting to kick in, of course, depends on the the quality of the amplifier (and other components too).

So, I guess, when you shoot you picture, you must be shooting in a low light environment or you simply set the camera's ISO too high.

http://dcfever.com/reviews/panasonic/fx01/page2.php
你拉到ISO 感光度測試
你會見到iso80同400既分別
iso400既時候
明顯見到一點點紅紅綠綠
呢d就係noise


可以參考下我另一個回答知識：

雜訊=noise
相片的感光度(iso)愈高
noise便會愈強

雜訊會降低圖片細膩
放大時會有一點點紅紅綠綠


以下是我上網找到的一篇不錯的相關文章,
由於CCD內在品質，當以慢速快門拍攝時，影像中會顯示雜訊，它以隨機分佈、色彩豔麗的畫素的形式出現。一般數位相機在長時間曝光(通常小於1/30產生)下會產生雜點(亦可稱之燒點)情況，產生原因是因為CCD在長時間曝光所產生的高熱造成，特別在低光源或慢速快門的情形下是相當容易產生雜點，有時受到電磁干擾也會有雜訊的現象。