适马 17-70mm F2.8-4 DC Macro OS HSM这只镜头怎么样？
推荐回答（4个）
下面这一大段文字是德国Photozne专业评测镜头的网站对Sigma1770的评价
The Sigma AF 17-70mm f/2.8-4 DC HSM OS remains a fairly obvious candidate for budget oriented consumers. It may not reach stellar performance levels but the resolution figures are generally very decent. However, you may try to avoid the f/2.8 setting at 17mm due to fairly soft corners and high vignetting. Like most standard zoom lenses it shows a pronounced degree of barrel distortion at 17mm whereas other focal lengths are less affected. Lateral CAs are comparatively well corrected. All-in-all the results are almost surprisingly similar to its predecessor.
简单列举一下要点
1. 性价比高
2. 画质和解析度比较中肯, 不是最高也不是最低, MTF基本保持在1500以上, 还算可以了
3. F2.8全开光圈, 锐度下降的比较厉害, 从MTF的测试结果来看, 光圈得在F4以上锐度才算可以
4. 17mm端中央筒形形变比较厉害, 相比于其他镜头而言
5. 17mm. 24mm端的色散(CA)比较严重, 其他焦段还好. 也就是说用这颗镜头拍摄的广角风景, 明暗边缘会有相对比较明显的紫边.
6. 这一点是我加的, 我个人很讨厌变焦镜头伸出来的部分是两截的! 呵呵.
总而言之结论就是, 这颗镜头是一颗比较中庸的镜头, 不是最好也不是最坏, 就这个价位而言能有这样的画质已经是很不错了.
然后是你提到的个体差异了, 副厂镜头由于无法像原厂镜头出厂的时候能精确校正, 所以副厂镜头跑焦的概率还是蛮高的, 其中以适马为最. 适马镜头跑焦是出了名的 ,所以大家在买适马镜头的时候一般都把自己的相机带过去, 一个个试, 呵呵.个体差异其中可见一斑. 所以你买的时候也要注意这一点.
如果决定要适马的话, 建议考虑一下更新款一些的
Sigma AF 17-50mm f/2.8 EX DC HSM OS
这个在成像素质上要比前者好太多了.
这个头性价比很高。锐度适中，跑焦往往是拍摄经验和技术问题。
说句实话锐度挺一般的…主要是全开蛮一般的…
至于跑不跑很难说 适马的跑焦情况不比腾龙少…低端机身买之前要谨慎挑选。
性价比比较高。但是肯定没有尼康的镜头好。用在尼康机身上，这是副厂镜头。有时候买来会发现卡口不是太协调，触电经常会虚接。这也是运气好与坏了。最好不要网购，尽量到实体店里亲自试用，挑最适合的，要开正规的发票，也是对自己的血汗钱的负责。
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