[yhleung]

有人知道數碼相機的ISO值是如何計算出來的?
印象中傳統相機的ISO值與菲林上感光顆粒密度成正比, 有根有據,
100就100, 200就200~ 但係DC既ISO就好似冇一條公式計出黎,
除左知道在同一部相機上ISO值越大, NOISE就越多之外,
兩部相機之間又如何比較呢? 如果連一個公認既標準都欠奉, 咁雜誌經常寫某某相機有ISO50, 最高可以去到ISO800, ISO1600, 又有何意義?

其實數碼相機上講ISO, 會唔會純粹係廠商同我地開既一個大大既玩笑呢?

[loyukfai]

AFAIK, the ISO ratings used on digital cameras should be more or less the same of films, with respect to light sensitivity. Though some models seem to be a little bit more or less sensitive than the rest.

Say for a given set of attributes (available light, subject's brightness, metering method used), with the same lens and the same ISO setting, two digital cameras should use the same shutter speed and aperture size, or a combination with equivalent EV.

Try Googling for "exposure light value" and there are more into the subject.

[ronail]

我個人認為係有條公式既,
如果唔係又點會有d機一黎就黎iso200呢?
講出黎都唔好聽la係咪?
所以我諗唔會係佢話係幾多就幾多既

[以相機作為武器]

我嚴重覺得在相同iso下
數碼機的雜訊比
傳統機的來得嚴重!!!

[老叟]

菲林有粒子粗幼問題,數碼有雜訊問題,情況唔同架!!
dc同DSLR既CCD構造又係唔同,dc去到ISO400雜訊好嚴重,但係DSLR,ISO100,同200根本無分別,就算去到800一樣好乾淨,如果係菲林就變左沙頭角村長個女喇!!

[loyukfai]

AFAIK, the construction of the sensor (CCD/CMOS) is more or less the same for consumer digicams and DSLR cameras, but since the size of DSLR's sensors are much larger, their "light wells" of each pixel are also much larger thus allows cleaner and sharper images.

The more pixels you pack in a given size of sensor, the more noisy the images will become. See the comparison of 5M vs 8M images for proof.