作者atropos ()
看板DSLR
标题Re: [闲聊] SONY CZ24-70/4 eprice测试
时间Wed Feb 5 23:28:06 2014
真是惭愧，重新翻了一下"Depth of field and Bokeh"
才发现在第三十二页的左侧有这麽一段文字
"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."
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 106.1.131.62
1F：推 dehors:之前就听说模铸非球面镜片散景会有洋葱圈 研削非球面镜片则 02/05 23:41
2F：→ dehors:没有 例如noctilux 50/1就没有洋葱圈 02/05 23:42
我的解读是研削仍可能会有(因为非球面的不规则性)，只是没有模铸那麽明显
3F：→ tudaer:所以是在铸模和polishing这两个过程都会造成... 02/05 23:45
4F：→ tudaer:那这样看到24-70/4那乱七八糟的样子，也可知道QC... 02/05 23:45
5F：→ tudaer:感谢astroops大的引用...那篇800年前下载来却没看，答案... 02/05 23:48
6F：→ tudaer:近在眼前...。也感谢eprice告知了SONY-CZ目前的...恩... 02/05 23:48
※ 编辑: atropos 来自: 106.1.131.62 (02/06 00:03)
7F：→ wasiwatery:noctilux 50/1本来就没有asph XD 02/06 00:13
8F：推 dehors:歹势 打太快 我是说第一代的noctilux 1.2那粒 02/06 00:19
9F：→ atropos:这段文字旁还有范例照显示入尘并非完全不影响影像 02/06 10:39
10F：→ tudaer:灰尘在光源散景上很重要，但也得看灰尘大小颗粒和程度 02/06 13:43
11F：→ tudaer:所但是一般时候的确入尘不影响，而且新镜头过一个月就开始 02/06 13:43
12F：→ tudaer:入尘，总不能每个月都抓来拆开清吧... 02/06 13:44
13F：→ tudaer:就算清洁，安装回去时都会造成更多灰尘，除非进标规实验室. 02/06 13:44