(EV詳解) Shutter: 1/90 sec, Aperture: F4.8, Meter: 9 EV

發表人明天發表於 2005-08-31, 11:55

Meter: 9 EV
即係咩呀?
:sorry:

發表人 **peterso** 發表於 2005-08-31, 12:01

+9EV 都測到光

發表人明天發表於 2005-08-31, 12:03

peterso 寫:+9EV 都測到光

http://www.dpreview.com/gallery/?galler ... x_samples/

我就係唔明

發表人 **Cam** 發表於 2005-08-31, 12:33

+9EV is the lighting measurement. If you look at the spec. of a camera, for the sensitivity of the autofocus sensor, it will normally quotes as +0.5EV to 18EV (or something similar) and thus this range is the normal lighting condition, and therefore +9EV is well within the normal lighting condition.

發表人明天發表於 2005-08-31, 12:44

Cam 寫:+9EV is the lighting measurement. If you look at the spec. of a camera, for the sensitivity of the autofocus sensor, it will normally quotes as +0.5EV to 18EV (or something similar) and thus this range is the normal lighting condition, and therefore +9EV is well within the normal lighting condition.

CAM SIR
可唔可以用中文講呀?
:sorry:

發表人 **小BB** 發表於 2005-08-31, 14:11

peterso 寫:+9EV 都測到光

點解會測唔到呢?

EV = Exposure Value

EV = 0 代表在ISO 100下用f/1 光圈，曝光1秒才可得到正常曝光。

EV每增加1，代表光度增加了一倍。

0EV X 2 = 1EV
1EV X 2 = 2EV
2EV X 2 = 3EV
.
.
.

e.g.

1EV 之下 f/1.4 、 1秒快門便可得出正常曝光
2EV 之下 f/2 、 1秒快門或 f/1.4、1/2秒均可得出正常曝光

餘此類推。

發表人 **小BB** 發表於 2005-08-31, 14:35

咁張貓相點解係9EV呢

相張用f/4.2、1/80S

f/1 > f/1.4 > f/2 > f/2.8 > f/4 = 4EV

1S > 1/2S > 1/4S > 1/8S > 1/16S > 1/32S =5EV

即係話f/4 x 1/32s = 9EV

但係由於佢用ISO250，於是乎可以用快級半左右快門，因此佢可以響9EV的光度下用f/4.2 x 1/80s

解錯唔好 :hit:

發表人 **射擊人** 發表於 2005-08-31, 14:49

好英呀~~你! 小BB! :a008:

發表人 **Cam** 發表於 2005-08-31, 15:19

射擊人寫:好英呀~~你! 小BB!

Yes, very very good and precise explanation. :a012:

To be honest, I have seen EV value in many places but never know exactly how it is defined. :a002:

I can add a bit of explanation also, as 小BB said, +2EV is twice as bright as +1EV, so this whole measurement is in logarithm scale.

As we know, exposure is a product of lens aperture x shutter openning time, and we all know that

log (ab) = log(a) + log(b)

That's why you can add 4EV + 5EV = 9EV

Also +9EV is the lighting condition when the picture was taken, you can have many aperture/shutter speed combinations (2+7, 3+6, 4+5, ...) as long as it adds up to 9EV.

發表人明天發表於 2005-08-31, 15:26

死
中文都唔明

發表人 **Cam** 發表於 2005-08-31, 15:46

OK, basically 0EV is very very dark. +9EV is reasonably bright.

If it is dark, then you need to open your shutter longer or have a bigger hole (aperture) in your lens in order to get the correct exposure.