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•the focus point shifts SUBSTANTIALLY when stopping down. Or in other words: the lens suffers from residual spherical aberrations (RSA). In close focus situations this is rather poisonous and the problem was affecting images taken at more conventional distances. The user who supplied the lens checked this behavior with a 2nd lens and this focus characteristic was the same here. This is NOT (sufficiently) compensated by the AF. We did AF reference checks during the MTF analysis and there's a decrease in measured resolution (= increase in focus shift) from f/4 to smaller apertures.
当缩小光圈时焦点显著漂移。换句话说,镜头存在残余球面偏差(RSA)。近距离对焦情况下这个问题十分令人讨厌,而且影响在更常见距离上的成像。提供测试镜头的使用者还检查了另一支镜头,发现相同的聚焦特性。这不是自动聚焦AF可以充分补偿的。我们在MTF分析过程中进行了AF的参考检查,在f/4向更小光圈变化时发现了实测分辨率的下降(相当于焦点漂移量的增加)。
在标尺焦点测试中发现,f4缩至5.6再缩至8,每次焦点会漂移1cm左右。
photozone在结论中称:该镜头分辨率非常锐,某些情况下甚至超越其同门师兄24-70f/2.8L II,但由于RSA问题,此镜头成像被扣分至3星,性价比2星半。
对此镜头一直十分关注,正在最后下决心阶段读到此测评,不得不急刹。恳请使用过此头或有条件测试的兄弟提供一手信息,到底是否存在上述跑焦问题?本人在此多谢了。
您的翻译我不是太理解,您的意思是加入设定F8光圈,对焦的时候镜头先是光圈F4,快门那一下才收缩到F8?
英文的关键词RSA,我查了下,应当翻译成残余球相差。英文的意思好像是对焦后焦点转移构图容易出现脱焦吧。---假如是这样,不是问题呀,任何广角近距离拍摄,中央对焦再构图的话都有这可能啊。
我之前有24-70/4L在F4光圈的测试。没感觉到跑焦,或者所说的RSA
http://bbs.fengniao.com/forum/2865687_4.html
不是跑焦,比跑焦还要麻烦。普通的跑焦是个别现象,可以通过校准或机内微调来决绝。而焦点偏移是随着光圈缩小而跑焦,因为对焦的时候都是在最大光圈时锁定的,光圈收缩后就会跑焦。不过也只有很小的机会遇到这个问题,因为F/4本来光圈就不是很大,而光圈收到一定程度景深说不定就盖过跑焦的距离了。如果经常用F/4然后不在很近的距离对焦就不会有影响~
The Canon EF 24-70mm f/4 USM L IS is a difficult being with a great technical performance and a worrisome focus characterstic. It is certainly capable of delivering a image quality that sometimes even surpasses its bigger in-house mate (EF 24-70mm f/2.8 USM L II). It is very sharp throughout the range with no significant weakness at any mainstream setting including max. aperture. The very low amount degree of lateral CAs contributes to the high sharpness perception. There is some noticeable light-falloff at f/4 but this is hardly surprising on a full format camera - the light falloff could be better at 24mm at medium aperture settings though. The distortion levels are moderate and slightly better than average for a lens in this class. The quality of the bokeh is pretty decent but not without flaws in certain situations. Given the moderate max. aperture there is not much bokeh fringing to speak of. The macro feature is pretty nice but avoid f/4 due to the substantial softness here but it is much better at medium aperture settings. The most worrisome flaws are, however, focus shifts - thus if you stop down the focus point is pushed towards the background (Residual spherical aberrations / RSA). This can be a game spoiler in some scenes (specifically close focus) which is also why we downgraded the otherwise very good optical quality.
Typical for modern Canon L lenses, the mechanical quality is a shining aspect, of course, but then you also expect no less from such a pricey beast. The compact size and comparatively low weight is certainly attractive compared to "the lead pipe" - thus the EF 24-70mm f/2.8 USM L II. Canon's USM drive offers an extremely fast AF and lack of noise is highly impressive. The image stabilizer is as efficient as we are used to from other Canon offerings.
However, given the RSA (focus shift) problem, we would rather recommend to go either for the Canon EF 24-70mm f/2.8 USM L II or even the lower performance Canon EF 24-105mm f/4 USM L IS instead.
photozone的结论哦,画质有时甚至超越24-70II,你看有没有夸张的说?
作者: JHXG 不是跑焦,比跑焦还要麻烦。普通的跑焦是个别现象,可以通过校准或机内微调来决绝。而焦点偏移是随着光圈缩小而跑焦,因为对焦的时候都是在最大光圈时锁定的,光圈收缩后就会跑焦。不过也只有很小的机会遇到这个问题... |
都是RAW直出,只压缩,原封未动,可参考下
The Canon EF 24-70mm f/4 USM L IS is a difficult being with a great technical performance and a worrisome focus characterstic. It is certainly capable of delivering a image quality that sometimes even surpasses its bigger in-house mate (EF 24-70mm f/2.8 USM L II). It is very sharp throughout the range with no significant weakness at any mainstream setting including max. aperture. The very low amount degree of lateral CAs contributes to the high sharpness perception. There is some noticeable light-falloff at f/4 but this is hardly surprising on a full format camera - the light falloff could be better at 24mm at medium aperture settings though. The distortion levels are moderate and slightly better than average for a lens in this class. The quality of the bokeh is pretty decent but not without flaws in certain situations. Given the moderate max. aperture there is not much bokeh fringing to speak of. The macro feature is pretty nice but avoid f/4 due to the substantial softness here but it is much better at medium aperture settings. The most worrisome flaws are, however, focus shifts - thus if you stop down the focus point is pushed towards the background (Residual spherical aberrations / RSA). This can be a game spoiler in some scenes (specifically close focus) which is also why we downgraded the otherwise very good optical quality.
Typical for modern Canon L lenses, the mechanical quality is a shining aspect, of course, but then you also expect no less from such a pricey beast. The compact size and comparatively low weight is certainly attractive compared to "the lead pipe" - thus the EF 24-70mm f/2.8 USM L II. Canon's USM drive offers an extremely fast AF and lack of noise is highly impressive. The image stabilizer is as efficient as we are used to from other Canon offerings.
However, given the RSA (focus shift) problem, we would rather recommend to go either for the Canon EF 24-70mm f/2.8 USM L II or even the lower performance Canon EF 24-105mm f/4 USM L IS instead.
photozone的结论哦,画质有时甚至超越24-70II,你看有没有夸张的说?
未能感觉到跑焦,不过测试跑焦应该是上架,然后地上放把尺子测试吧。
对于我,我只需要他指哪里就打哪里就可以了,至于那些专业性的测试相信会有高手大师跟进吧。
楼上上传不了????
我这里放了更多的24-70/4L的照片,同时也想向各位高人了解什么是RSA
http://bbs.fengniao.com/forum/2865687_4.html
未能感觉到跑焦,不过测试跑焦应该是上架,然后地上放把尺子测试吧。
对于我,我只需要他指哪里就打哪里就可以了,至于那些专业性的测试相信会有高手大师跟进吧。
啊哈哈,微距方面我没经验。
不过这个头微距很不方便,对焦距离太近了(近到,假如戴上遮光罩的话都几乎碰上拍摄物了),而且放大程度还不如小白兔套上xpro。这个头微距我觉得真是很一般。
这个头我感觉是佳能比较激进的产品,微距功能似乎是实验性的,虽然是个宣传点,但感觉没把这个功能打到价格上,所以如果RSA只是微距受影响的话,那我就不去理会了。
小白和xxbis差价1000左右(二者画质相差不大),70F2.8I代贵70F4is&MACRO不止1000了(F4is画质上、对焦。。。较I代好不少接近甚至超过II代),II代的差价就更不用说了,这是我买这个头前做功课时其中一个想法。
多谢肚腩兄的信息。不知你是否试过用小光圈拍微距?如果有RSA,当退到f8时有可能焦点已经跑老远了,对微距来说可能完全失败。
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