[calvinchiu]

請問係咪有equation可以把dc 的焦距 convert 成菲林機的 mm?

e.g
http://www.dcfever.com/gallery/viewphoto.php?galleryID=114&page=1&picID=156

呢度(dcfever webpage) 寫焦距 = 280mm
但我睇exif info 時焦距係 = 71.2mm

請指教

[香港至NET超人]

http://www.wpiinc.com/WPI_Web/Microscopy/C-Mounts/c-mount_direct.html
diagonal of 135
--------------------- X focal length on DC = equivalent focal length on 135
diagonal of CCD

Example: The 7mm lens on Dimage 7 (2/3" CCD) is equal to:
7mm x 43mm / 11mm =~= 27.4mm

Because most CCD cannot use up the whole imaging area to the edges,
the equivalent focal length should be a bit tele. While DC has 100%view
and most 135 SLR don’t (so as the crop out of 3R print), you would find
that DC images look a bit wider than corresponding SLR images in finder
or photos.

[dede]

謝謝超人兄所提供此有用公式。煩再多指點一二

1/2 in的 CCD 己從上述網站得知，其對角線是８mm

但通常的 CCD 是 1/1.8 in，那麼從何得知它的對角線呢，因不知長與高的數据，不能計算出來。而 1/1.8 in 的大小是否指面積與 35mm 菲林的面積來比較的，那麼無法求出長?來啊，
我的 S602z又是 1/1.7 in，通常廠商沒有提供長ｘ?是幾多，如知道長?，便能計算出其對角線，35mm 的對角線已知是 43mm(取其整數)，已可算是一恆定數，再知埋自己個 CCD 的對角線，便可代入你所提供的公式來算出當時拍攝所用的是幾多焦距（是說相當於 35mm 菲林的），因每次拍攝後從 exif 得知的焦距是 DC的實際焦距，很想換算成 35mm 的焦距啊。

在此先謝謝超人兄

[calvinchiu]

非常多謝超人兄及dede兄 (因為我都唔知35mm 的對角線是43mm)~
我初初仲以為1/3" ccd 係指 個ccd 的diagonal length 係有1/3 inch... 但原來唔係ga wo... ; )

真係學到好多野!

[calvinchiu]

dede 兄..
請看看這樣幫唔幫到你:

f = focal length
d = ccd diagonal size
m = equivalent focal length on 135

we have:
m = f * 43 / d
therefore,
d = f * 43 / m

1. try to use the widest zoom (no zoom) to shot a picture. then in the EXIF info get the focal length (so we have f = ? now)

2. in DCfever.com, your camera's widest focal length is 35mm
(http://www.dcfever.com/cameras/specification.php?CameraID=188)
(now we have m = 35 too)

3. subst. f and m in the equation, then we can get d.

如有錯灟請更正

[dede]

f = focal length（CCD）
d = ccd diagonal size
m = equivalent focal length on 135

we have:
m = f * 43 / d（公式一，由超人兄提供）
therefore,
d = f * 43 / m（公式二，由 calvinchiu兄換算得來）

己知（廠商提供）：
S602z際焦距是由 7.8mm to 46.8mm (6X=7.8mm x 6 = 46.8mm)
相當於 35mm 菲林機的 35mm to 210mm

代入以上公式二：
d = 7.8mm x 43/35mm = 9.58mm（最 wide 時）
d = 46.8mm x 43/210mm = 9.58mm（最 tele 時）

因此証明你的求對角線的公式是對的，真好呀，知道了自己的 CCD 的對角線便可

根据拍攝資料 exif，用公式一來計算出每張相的相當於 35mm 菲林機的焦距了。

在此謝謝超人兄及 calvinchiu兄。

[dede]

35mm 的對角線是這樣計算得來的（直角三角形的斜邊）
A = 35mm 的長
B = 35mm 的?\nC = 對角線

C=sq.root(A sq + B sq)

c=sq.root(1225+576)=42.44mm（超人兄當 43mm 也可，冇所謂，不用太準都冇問題）

[香港至NET超人]

35MM菲林對角長 == SQRT(24^2 + 36^2) == 43.2666MM
因為135的菲林面積是24mm x 36mm.
(1/2")不是那隻ccd的對角長, 而是n-年前習慣用video camera的鏡頭卡口大細, 詳細spec我找不到, 但那一如習慣而已, 無須深究. 至於出現1/2.7"之類的號數, google.com吧.
http://www.sony.net/Products/SC-HP/CXPAL/CXNEWS-28/PDF/ICX432np.pdf

[dede]

因為135的菲林面積是24mm x 36mm，我以為是24mm x 35mm，所以計錯數，
原來 CCD 的 xxx 大小也不是說面積，咁看來菲林的 35mm 所指也不是了。

再次多謝超人兄的更正

[calvinchiu]

超人兄很強悍啊...

dede 兄.. 我搵到呢個相關網頁... 但都係冇 1/1.7"

http://www.dpreview.com/news/0210/02100402sensorsizes.asp

[香港至NET超人]

The 35mm of 135 film is about the width of the film. There is also 70mm film which looks like 135 with spot holes at the edge, it is 70mm width.
Originally, 35mm film is mostly use for movie taking. The earliest 135 film camera is using 18mm X 24mm and it is called single frame. Lecia make use of this film and build 135 camera with 24 mm X 36mm which is called double frame. After quite sometimes of using the double frame, no one go back to use single film as it got double the resolution and less film grain. The single frame back to the world in 80's. After the success of Kodak Disc, some of the companies use back the single frame format to make all-in-one camera with double number of shots. Well, they call it the half frame which is very much likely that "single frame" is too commonly be known as 24x36.

[dede]

超人兄，謝謝你不厭其煩的詳說，你所提的公式己夠用了。

calvinchiu兄，不用找啦，你提供的換算法己可計算出任何的大小CCD的對角線了（我上面己計算出 602z 的 1/1.8in 的對角線）。謝謝你為我費上了你的寶貴時間。

[calvinchiu]

^_^
因為我對這個ccd size 的由來充滿curiosity, 所以都想知多d ~
都係順道, 唔洗客氣~ :)