2024年11月6日发(作者：邛高远)
Introduction
Pentax has quite a reputation regarding street photography thanks to their extensive "Limited" lens lineup
which covers the range from moderate wide-angles to moderate tele. These lenses aren't exactly cheap but
ultra compact and high quality items. The Pentax SMC DA 40mm f/2.8 Limited is one of these lenses.
Looking at its shape it is quite obvious why it is called a pancake lens - it is as flat. Just like most current
Pentax lenses it is a DA lenses with a reduced image circle dedicated to the APS-C format. Its field-of-view
is equivalent to 60mm on full format cameras. Now this is a bit of a problem because "60mm" f/2.8 isn't
exactly in the sweet spot of user desires. Fortunately Pentax was at least sane enough to keep the price level
to a relatively moderate degree.
引言
宾得在街拍享有相当的威望是因为他完整的“Limited”饼干头产品阵线——焦段跨越中广角到中长焦。这些镜头并不算便
制作工作精良。看它的大小就知道为啥它叫饼干头了，跟饼干差不多薄。
宜，但是体积非常娇小，DA40是饼干头中的一支。
它是
da些列的，和很多宾得现产的镜头一样，既专门为APS-C画幅优化的的数码头。它等效焦距为全副机器上的60mm。
幸运的是宾得比较明智的把价格定在相对温和的价位。
这就存在一个小问题了，60mm f/2.8并不是很多用户的最佳视角。
Thanks to the extensive use of metal rather than plastics the build quality of the lens is excellent. The focus
control ring of the tiny lens seems to be made for elfs but then there's simply not enough space for anything
bigger.
多亏了用的是金属材质而不是所料材质，镜头制造工艺非常棒。镜头上的对焦环似乎是为小精灵做的，没
有足够的空间做的更大了。
Typical for most Pentax lenses the DA 40mm f/2.8 has no internal AF motor and relies on a slotted drive
screw operated by the camera. Consequently AF operations generate a moderate degree of noise. The AF
speed is very fast on the K10D - finally the focus group is about as light-weight as it gets. The focus accuracy
of the tested sample was excellent.
和大多数宾得镜头一样，da40没有内置对焦马达，依赖机身的卡槽的驱动，因此对焦时会产生一定的噪音。对焦速度在
K10D上非常快，对焦部分做得不能再轻了。测试样张上的对焦精度非常棒。
Distortions
Typical for standard/normal lenses the Pentax DA 40mm exhibits only a minor degree of barrel distortions
(~0.6%) - nothing to worry about under field conditions.
畸变
和大部分标头一样，da40只呈现了轻微的桶形畸变（~6%），现场拍摄根本不需要担心。
Vignetting
Regarding its APS-C image circle it doesn't really surprise that the DA 40mm f/2.8 produces a some
vignetting at wide-open aperture (0.9EV). At f/4 the problem is already greatly reduced and it's negligible
from f/4 onwards.
暗角
所以
da40全开光圈产生一些暗角并不惊奇考虑到APS-C画幅，（0.9EV）。f/4之后暗角大量减少，f/4之后暗角可忽略。
MTF (resolution)
Pancake lenses have the reputation to produce a very even resolution across the frame but at cost of peak
performance. The Pentax DA 40mm f/2.8 Limited is indeed not as sharp as its direct cousins but frankly the
difference is not really detectable by the naked eye. In the lab the lens was a already able to deliver very
good results at f/2.8 and an excellent quality between f/4 and f/8. Typical for all lenses diffraction reduces
the quality from f/11 onwards. The sweet spot is at f/5.6.
MTF（分辨率）测试
饼干镜头以分辨率均匀而名声在外，但是损失了些峰值表现。DA40确实没有FA43那般锐利，但是裸眼看
不出来差距。实验室测试中，f/2.8已经能给出非常好的评价了，在f/4到f/8之间则是优秀。和大多数镜
头一样f/11之后质量下降，最好的点则是在f/5.6。
Chromatic Aberrations (CAs)
Lateral chromatic aberrations (color shadows at harsh contrast transitions) are a non-issue of the Pentax. A
rare but very welcome characteristic.
色散测试
da40的色散基本没问题，色散很少，特性很好。
Verdict
The Pentax SMC DA 40mm f/2.8 exhibits a very harmonious optical performance combined with excellent
build quality. It is capable to produce very sharp images across the frame straight from the max. aperture.
Distortions are marginal and CAs are a non-issue. Vignetting is quite pronounced at f/2.8 but not a
show-stopper. The bokeh (out-of-focus blur) is pretty smooth. The biggest "problem" of the lens is not
quality but its application. It is a comparatively slow lens and not faster than many zooms and classic
"normal" lenses are about as good at comparable apertures but with a lot more potential for low light
photography ... at a lower price. Some users may argue with its size and weight but even with the DA 40mm
f/2.8 a DSLR is not a pocketable camera. That all said it remains an excellent performer and as such it is a
welcome addition to the Pentax lens lineup.
结论
DA40有非常和谐的光学表现，并有着非常优秀的制造工艺。
从最大光圈开始就能出非常锐利的照片，畸变微小，色散控制
不存在问题，暗角在f/2.8时较为明显但是并不会影响画面表现，焦外相当顺滑。Da40最大的问题不是质量而是它的适用
性。对焦和很多变焦镜头、经典的表头相比并不快，和这些镜头在同等光圈下的表现差不多，但是这些镜头在弱光还有余地
（因为这些经典标头他们最大光圈一般在f/1.4到f/2），这些镜头相对DA40还要便宜些。但是DA40仍然是一支非常好
的镜头。
样张：
西川和久的糖水样张：
2024年11月6日发(作者：邛高远)
Introduction
Pentax has quite a reputation regarding street photography thanks to their extensive "Limited" lens lineup
which covers the range from moderate wide-angles to moderate tele. These lenses aren't exactly cheap but
ultra compact and high quality items. The Pentax SMC DA 40mm f/2.8 Limited is one of these lenses.
Looking at its shape it is quite obvious why it is called a pancake lens - it is as flat. Just like most current
Pentax lenses it is a DA lenses with a reduced image circle dedicated to the APS-C format. Its field-of-view
is equivalent to 60mm on full format cameras. Now this is a bit of a problem because "60mm" f/2.8 isn't
exactly in the sweet spot of user desires. Fortunately Pentax was at least sane enough to keep the price level
to a relatively moderate degree.
引言
宾得在街拍享有相当的威望是因为他完整的“Limited”饼干头产品阵线——焦段跨越中广角到中长焦。这些镜头并不算便
制作工作精良。看它的大小就知道为啥它叫饼干头了，跟饼干差不多薄。
宜，但是体积非常娇小，DA40是饼干头中的一支。
它是
da些列的，和很多宾得现产的镜头一样，既专门为APS-C画幅优化的的数码头。它等效焦距为全副机器上的60mm。
幸运的是宾得比较明智的把价格定在相对温和的价位。
这就存在一个小问题了，60mm f/2.8并不是很多用户的最佳视角。
Thanks to the extensive use of metal rather than plastics the build quality of the lens is excellent. The focus
control ring of the tiny lens seems to be made for elfs but then there's simply not enough space for anything
bigger.
多亏了用的是金属材质而不是所料材质，镜头制造工艺非常棒。镜头上的对焦环似乎是为小精灵做的，没
有足够的空间做的更大了。
Typical for most Pentax lenses the DA 40mm f/2.8 has no internal AF motor and relies on a slotted drive
screw operated by the camera. Consequently AF operations generate a moderate degree of noise. The AF
speed is very fast on the K10D - finally the focus group is about as light-weight as it gets. The focus accuracy
of the tested sample was excellent.
和大多数宾得镜头一样，da40没有内置对焦马达，依赖机身的卡槽的驱动，因此对焦时会产生一定的噪音。对焦速度在
K10D上非常快，对焦部分做得不能再轻了。测试样张上的对焦精度非常棒。
Distortions
Typical for standard/normal lenses the Pentax DA 40mm exhibits only a minor degree of barrel distortions
(~0.6%) - nothing to worry about under field conditions.
畸变
和大部分标头一样，da40只呈现了轻微的桶形畸变（~6%），现场拍摄根本不需要担心。
Vignetting
Regarding its APS-C image circle it doesn't really surprise that the DA 40mm f/2.8 produces a some
vignetting at wide-open aperture (0.9EV). At f/4 the problem is already greatly reduced and it's negligible
from f/4 onwards.
暗角
所以
da40全开光圈产生一些暗角并不惊奇考虑到APS-C画幅，（0.9EV）。f/4之后暗角大量减少，f/4之后暗角可忽略。
MTF (resolution)
Pancake lenses have the reputation to produce a very even resolution across the frame but at cost of peak
performance. The Pentax DA 40mm f/2.8 Limited is indeed not as sharp as its direct cousins but frankly the
difference is not really detectable by the naked eye. In the lab the lens was a already able to deliver very
good results at f/2.8 and an excellent quality between f/4 and f/8. Typical for all lenses diffraction reduces
the quality from f/11 onwards. The sweet spot is at f/5.6.
MTF（分辨率）测试
饼干镜头以分辨率均匀而名声在外，但是损失了些峰值表现。DA40确实没有FA43那般锐利，但是裸眼看
不出来差距。实验室测试中，f/2.8已经能给出非常好的评价了，在f/4到f/8之间则是优秀。和大多数镜
头一样f/11之后质量下降，最好的点则是在f/5.6。
Chromatic Aberrations (CAs)
Lateral chromatic aberrations (color shadows at harsh contrast transitions) are a non-issue of the Pentax. A
rare but very welcome characteristic.
色散测试
da40的色散基本没问题，色散很少，特性很好。
Verdict
The Pentax SMC DA 40mm f/2.8 exhibits a very harmonious optical performance combined with excellent
build quality. It is capable to produce very sharp images across the frame straight from the max. aperture.
Distortions are marginal and CAs are a non-issue. Vignetting is quite pronounced at f/2.8 but not a
show-stopper. The bokeh (out-of-focus blur) is pretty smooth. The biggest "problem" of the lens is not
quality but its application. It is a comparatively slow lens and not faster than many zooms and classic
"normal" lenses are about as good at comparable apertures but with a lot more potential for low light
photography ... at a lower price. Some users may argue with its size and weight but even with the DA 40mm
f/2.8 a DSLR is not a pocketable camera. That all said it remains an excellent performer and as such it is a
welcome addition to the Pentax lens lineup.
结论
DA40有非常和谐的光学表现，并有着非常优秀的制造工艺。
从最大光圈开始就能出非常锐利的照片，畸变微小，色散控制
不存在问题，暗角在f/2.8时较为明显但是并不会影响画面表现，焦外相当顺滑。Da40最大的问题不是质量而是它的适用
性。对焦和很多变焦镜头、经典的表头相比并不快，和这些镜头在同等光圈下的表现差不多，但是这些镜头在弱光还有余地
（因为这些经典标头他们最大光圈一般在f/1.4到f/2），这些镜头相对DA40还要便宜些。但是DA40仍然是一支非常好
的镜头。
样张：
西川和久的糖水样张：