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b*****s
发帖数: 3390 | 1 “Autofocus in video can exhibit focus hunting” 看来拍业余拍拍视频还是选择
索尼和佳能比较好，平滑性可以得到保证。
Autofocus in video is noticeably improved form the GH4, but even with
improved DFD technology the camera still doesn't have a true sense of depth
like it would with a phase detection system. As a result, the camera still
has a tendency to hunt for focus, creating a wobble as focus ratchets back
and forth.
You won't see the huge, obvious swings in focus we traditionally associate
with contrast detect AF, but a more subtle wobble or shake. In certain
situations you may not even notice it, but in others – for example, when
you have slightly out of focus point sources of light in the background –
it can be quite noticeable. The video clip above shows an example of this
phenomena: the neon sign in the background wobbles as the camera tries to
maintain focus.
We can't help but feel this may be a missed opportunity for Panasonic. Over
the past couple years we've seen very effective on-sensor phase detect
systems for video, including Canon's dual pixel autofocus, as well as the AF
system on the Sony a6300/a6500 twins. Panasonic's insistence on sticking
with DFD autofocus technology for a camera primarily aimed at video shooters
doesn't seem to be the best choice, and takes away from what is otherwise a
very good video camera.
As with any AF system, there's still enough variability when shooting video
that you'll probably want to stick with manual focus for very precise work,
such as narrative filmmaking, but a good AF system is really important for
things like documentary shooting, or even family get togethers, where motion
is less predictable. You can certainly use the GH5 in these situations, but
it some cases it may produce some subtle, though noticeable, focus hunting. | k**********s
发帖数: 6409 | 2 用过松下好几年，就是因为它当时是录像对焦最少拉风箱的。转到索尼是图其有防抖的
标准定焦好录像，没想到录像对焦更是梦寐以求的完美无缺。 | y*b
发帖数: 3190 | 3 最好的估计还是dual pixel. 有rumor说，Sony也在搞dual pixel.
【在 k**********s 的大作中提到】
: 用过松下好几年，就是因为它当时是录像对焦最少拉风箱的。转到索尼是图其有防抖的
: 标准定焦好录像，没想到录像对焦更是梦寐以求的完美无缺。
| b*****s
发帖数: 3390 | 4 之前大家视频都用反差对焦，这方面奥巴和松下因为43就开始发展反差对焦，所以技术
积累最多，这一点也不奇怪。
现在佳能索尼富士都采用相位对焦，相位对焦在追焦方面原理性秒杀反差对焦了
我看到有人推测说松下4K视频因为处理器数据量太大，所以处理器（或者寄存器缓存器
）无法在追焦（时刻需要识别焦点）上分工太多（因为反差也好dfd也好，都是需要高
度依赖高刷新率多帧图像中由处理器识别峰值来达到对焦）。GH4/5都存在这个问题，5
处理器略强，所以会比4好一些，但是还是比较明显。
基于过去对松下gh1-3的认识，gh4一直性价比还可以，我也是一直比较推崇松下的GH系
列，看来原理性的东西根本无法绕过，要视频平滑，相位对焦是必须的。
【在 k**********s 的大作中提到】
: 用过松下好几年，就是因为它当时是录像对焦最少拉风箱的。转到索尼是图其有防抖的
: 标准定焦好录像，没想到录像对焦更是梦寐以求的完美无缺。
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