[tommywhite03]

請教各位師兄
(假設有兩件物件分別位於 Model 前、後同等距離，前景的景物是會比背景的景物模糊。)Copy From Dcfever

[eternity1006]

大家都知道一般相機要對焦後才能拍攝，理論上相片中只有被準確對焦的部分（焦點）清晰，焦點前及焦點後的景物會因在焦點以外而顯得模糊。不過，基於鏡頭、拍攝距離等因素，在焦點前、後仍然會有一段距離的景物能夠被清晰顯示，不致於落入模糊地帶，這個清晰的範圍便稱為景深。

(COPY FROM DCFEVER)

如果你係點解淺景深既時候焦區內清淅而非焦區內(前及後)會糢糊,呢樣咁technical既野我都答你唔到......呢類應該係光學原理問題.

[mochida]

佢應該係問緊對焦點前後模糊既地方，相同距離開之下點解會係前面比後面模糊，而唔係一樣咁模？

[eternity1006]

OIC....請參考這個~ http://www.dchome.net/viewtopic.php?p=1812669 "甚麼是焦距"

[eternity1006]

根據焦點區原理,當找到一個焦點所在時,就同時會產生前糊區同後糊區,本應兩者幅度相同,但因前糊區比後糊區更接近你所在位置,基於視角差距前糊區應比後糊區的影像更為糢糊.

[zeusho]

To tommywhite03朋友：

以下的網址應該對你有用：

http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/950/depth-of-field.html

DOFMaster - DEPTH OF FIELD CALCULATORS

http://www.dofmaster.com/dofjs.html

[tam_dominic]

Because the closer the less depth of field.
In my understanding the ideal depth of field is something like this :
-----|-------

In my 350D sometimes like this :
----------|--
sometimes like this :
---|---------

I guess it is something to do with the stepping motor.
The larger the step the worse the focus accuracy.

The focusing system try to focus step by step.
When it cannot focus it move to next step until it can focus.
The larger the step the faster the object get focused.
In all above cases the object is focused because it is within the depth of field.

Sorry off topic

[小小生]

最簡單的講法係,因為越遠的物件在你看來會越細
所以近的物件化開少少你已經覺得它不是一點,但較遠的物件就算化開得較大在你看來它仍然是一點

[tommywhite03]

多謝各位大師兄！

[D.S]

小弟完全同意eternity1006兄的說法,因小弟都讀過下攝影原理,在物件in focus的前後區域,稱之為焦點深度,前焦點深度和後焦點深度,一般來說後區的景深會比前區長,大約1:2,原因是大家都應該知道如何可以拍人像獲得一張淺景深的photo以突出主題,1.拍攝距離 2.光圈大小 3.焦距長短
如果2,3為之不變,因為前焦點深度的物件比後的更接近鏡頭,所以景深會較淺.