b*******t
发帖数: 33714 | 1 有人用过aspheric lens么？差别明显么？ | z****6
发帖数: 10776 | 2 cv35/1.7算吗？
【在 b*******t 的大作中提到】
: 有人用过aspheric lens么？差别明显么？
| b*******t
发帖数: 33714 | 3 跟类似的spherical lens比较过么？相差上差别明显么？？
【在 z****6 的大作中提到】
: cv35/1.7算吗？
| b****r
发帖数: 17995 | 4 现在好点的镜头都非球面吧，特别是广角一点的非鱼眼头 | C****c
发帖数: 9157 | 5 好多狗头也都是非球了
反正都是铸模的
手工研磨的非球比较牛逼
【在 b****r 的大作中提到】
: 现在好点的镜头都非球面吧，特别是广角一点的非鱼眼头
| b*******t
发帖数: 33714 | 6 这一段有点意思：
What are the advantages of the PGM aspherical lens compared with the
precision-ground aspherical lens and the hybrid lens?
Sakuma:
Since plastic is used in the hybrid lens, it is subject to environmental
changes such as temperature and humidity fluctuations. However, such changes
have a negligible affect on molded glass lenses. As for a precision-ground
lens, the process of directly grinding the glass takes time and is therefore
not suited for mass production. Since a molded glass lens is made by
pressing softened glass into a die, it is possible to make a lens in a short
time.
Sensui:
Another advantage of the PGM aspherical lens is its high refractive index.
Lenses with higher refractive indexes perform better. Since glass that
refracts well is hard and expensive, if it is ground, the grinding elements
wear out quickly, making the production of even one lens extremely expensive
. With molded glass, however, costs can be kept down, which is highly
advantageous in the area of optical design where several elements are used
in a single lens. Moreover, grinding marks appear in the bokeh areas on
precision-ground lenses. This does not happen at all with molded glass.
Nikon no longer uses the precision-ground method for making aspherical
lenses for photography.
Sakuma:
The glass molding technique used to be more expensive than the hybrid method
, but that difference has recently narrowed with small-diameter lenses.
There is no apparent cost advantage yet with molded glass, but it may happen
in the near future.
http://imaging.nikon.com/history/scenes/25/index.htm
【在 C****c 的大作中提到】
: 好多狗头也都是非球了
: 反正都是铸模的
: 手工研磨的非球比较牛逼
| b*******t
发帖数: 33714 | 7 尼康做过很多aspherical lens么
changes
ground
therefore
short
【在 b*******t 的大作中提到】
: 这一段有点意思：
: What are the advantages of the PGM aspherical lens compared with the
: precision-ground aspherical lens and the hybrid lens?
: Sakuma:
: Since plastic is used in the hybrid lens, it is subject to environmental
: changes such as temperature and humidity fluctuations. However, such changes
: have a negligible affect on molded glass lenses. As for a precision-ground
: lens, the process of directly grinding the glass takes time and is therefore
: not suited for mass production. Since a molded glass lens is made by
: pressing softened glass into a die, it is possible to make a lens in a short
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