作者atropos ()
看板DSLR
標題Re: [閒聊] SONY CZ24-70/4 eprice測試
時間Wed Feb 5 23:28:06 2014
真是慚愧，重新翻了一下"Depth of field and Bokeh"
才發現在第三十二頁的左側有這麼一段文字
"If you look at this picture very closely, you can see another interesting
effect – all the defocused spot images contain a circular structure. It is
possible to recognise from this that the lens has an aspherical surface as
these surfaces are often not as smooth as a conventionally polished lens.
Particularly in the case of lenses which are manufactured by pressing hot
liquid glass it is possible to recognise the traces of the turning process
with which the mould was manufactured.
It is possible to combine rotational and pivotal movements when polishing
spherical surfaces because the curvature of the surface is the same
everywhere; in this case no traces are left. In the case of aspherical
surfaces the curvature is variable and therefore demands other processing
techniques. Residual unevenness of these surfaces becomes visible if a very
small light source is reproduced very much out of focus."
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 106.1.131.62
1F：推 dehors:之前就聽說模鑄非球面鏡片散景會有洋蔥圈 研削非球面鏡片則 02/05 23:41
2F：→ dehors:沒有 例如noctilux 50/1就沒有洋蔥圈 02/05 23:42
我的解讀是研削仍可能會有(因為非球面的不規則性)，只是沒有模鑄那麼明顯
3F：→ tudaer:所以是在鑄模和polishing這兩個過程都會造成... 02/05 23:45
4F：→ tudaer:那這樣看到24-70/4那亂七八糟的樣子，也可知道QC... 02/05 23:45
5F：→ tudaer:感謝astroops大的引用...那篇800年前下載來卻沒看，答案... 02/05 23:48
6F：→ tudaer:近在眼前...。也感謝eprice告知了SONY-CZ目前的...恩... 02/05 23:48
※ 編輯: atropos 來自: 106.1.131.62 (02/06 00:03)
7F：→ wasiwatery:noctilux 50/1本來就沒有asph XD 02/06 00:13
8F：推 dehors:歹勢 打太快 我是說第一代的noctilux 1.2那粒 02/06 00:19
9F：→ atropos:這段文字旁還有範例照顯示入塵並非完全不影響影像 02/06 10:39
10F：→ tudaer:灰塵在光源散景上很重要，但也得看灰塵大小顆粒和程度 02/06 13:43
11F：→ tudaer:所但是一般時候的確入塵不影響，而且新鏡頭過一個月就開始 02/06 13:43
12F：→ tudaer:入塵，總不能每個月都抓來拆開清吧... 02/06 13:44
13F：→ tudaer:就算清潔，安裝回去時都會造成更多灰塵，除非進標規實驗室. 02/06 13:44