[vincentmhf]

即係部相機個光圈值 2.0 好過 2.8 ?
可唔可以解釋一下?

唔該哂咁多位願意reply『小弟』的人仕!! :)

[hiboy]

首先光圈越大, 光圈值越細, e.g. F/2.8大過F/8
唔同size光圈有唔同用途.
大光圈可以同一時間俾更多光線進入, 所以夜攝比較有利. 同時, 大光圈可以有效營造淺景深(值得一提ge係dc大多數都做唔到)
而細光圈就可以影到好深ge景深, 即拍攝景物完全清晰, 多數用於風景拍攝.
至於夜景都會選用細光圈加腳架.
所以光圈個range越大越方便.

[dclkwok]

光卷值 is ratio "focal length of the lens / aperture of the 光卷 at that particular instant". therefore, greater of the aperture smaller is the 光卷值. Understand? the statement "即係部相機個光圈值 2.0 好過 2.8 ?" is not 100 %. you can't compare unless the focal length of two lens are the same. ie, you can't compare 50 mm F 2.0 with 400 mm F4.

[wilwilson2003]

所以光圈愈細,結像力便愈高.

[Velsper]

>>所以光圈愈細,結像力便愈高.
也不完全對的~
解像力和深景深也是不同

[hkhei]

事實上，當光圈細到f22或者更細o既時候
解像力會受到diffraction 影響....
呢個時候解像力會因光圈縮小而下降

[ninekit]

vincentmhf hing, generally speaking your statement is correct, the smaller the f number means the bigger the opening the lens for light to come in and get your film to expose.

so given the same focal length, the smaller the f number of your lens, means you can open it wider for shorter exposure time. which in other words, increase your flexibility.

and in general, since its more costly to make a bigger piece of perfect optical glass, big aperture lens will be more expensive, but in general, their optical quality will be better than the same brand, smaller brother of the same focal length. there are exceptions but very rare, so rule of thumb, you pay more for a big aperture lens, you get more flexibility as there are more combinations of shutter speed you can use, and you get a lens of better quality. but the cost is the higher price you have paid and the extra weight for the bigger pieces of glasses.

then sorry for off-topic, Velsper hing, know you are using D7up (same as my brother), just wonder had u tried Neatimage to help on the high ISO noise? if not, i think its worth a look.

here is a link for the examples,

http://www.neatimage.com/examples.html

9kit

[hiboy]

如果睇開網站測試slr鏡頭, 一般細光圈測試只係會去到F/8

[Velsper]

9kit兄~(100x thanks ^ ^)
小弟沒有用neatimage
因聽說neatimage對相片會blur少少
(D7相對已經唔係好sharp...)

所以小弟平時會用5mp影相
高iso時就縮圖, D noise睇落會少D ^__^
(看過外國一個網站,ISO高時將image sharpness set做"soft"
再EV+0.3去"壓低dnoise, 你也可以一試~)

9kit兄你有沒有用過neatimage?

[ninekit]

Velsper hing, haven't try out NI yet, but very keen to have a go. problem is I have two PC, one fast desktop and a slow notebook, currently only the latter is hooked up with the internet, so its going to be tricky for me to download the trial version.
But today I just received another bluetooth key which can allow both of the PC to be hooked. he.. he... (then I can icq my wife at home. ^^)
Neatimage could be useful for me to reduce high ISO noise of my CP5000 as well as reduce the ugly grains appeared on my scanned image from pictures taken with some cheappy Konica Centura 200 film.
The other thing I also just received a Transcend 512MB CF card from my buddy, so next outing i can shoot all in RAW mode lu. :)

[Double Bass]

DC做不到淺景深.你可以用手動對焦對前一些(若果你的鏡頭沒有景深表便要靠目視了,例如50mm焦距,f8,對焦在2呎時,景深由1.9呎至2.1呎,若果改變對焦在1.8呎,由景深表顯示由1.7至1.9呎是落在清晰範圍,原來2.1呎的地方理論上已在景深清晰範圍之外.那麼在2呎之外的背景便會較為矇一些

話說當年錦囊有f1甚至f0.8鏡頭,當然主要用在超8糎電影機上啦

[vincentmhf]

哦~~~~~~~~~~~~~~~~~~~~~~
得到咁多位人兄教路,小弟已經好明白喇!!
真係非常感激!

(原來唔叫小妹都會有人reply既~ hehe)