妻弟试机照

Stone

俺的CF卡是4GB Transcend 266X. 是40D带过来的，在7D上并没有试过打机关枪。 ...
moonbay 发表于 2010-8-31 14:19

266X不错啊， 有22MB/s了！ 试试连发能不能到8fps？

袜贩

看到一个论坛里讲7D一定要用20MB/s以上的memory卡 （如SanDisk Extreme IV）， 否则8fps的连拍速度达不到 ...
Stone 发表于 2010-8-31 16:05

这个说法恐怕不对。 我的理解是连拍速度和CF卡的存取速度并没有必然的联系。相机连拍时，拍下的照片都是暂时存在memory buffer里，而不是直接存到卡上。每个相机都有个buffer size。而且当今最快的CF卡也不可能每秒存8张照片。

moonbay

这个说法恐怕不对。 我的理解是连拍速度和CF卡的存取速度并没有必然的联系。相机连拍时，拍下的照片都是 ...
袜贩 发表于 2010-9-1 06:40

    按您的意思，俺就不必劳神了？

这是网上找的资料。他们说的是用妻弟录像多少速度的卡足够快。

A question that frequently pops up when people want to shoot video with their Canon EOS 7D is regarding the required minimum speed of the Compact Flash card. Card speed is usually specified in “x” ratings, e.g. 8x, 20x, 133x. This is the same system used for CD-ROMs and gives the data rate as a multiple of the data rate of the first CD-ROMs (i.e. the data rate of an audio CD). The base rate is 150 kB/s, so for example, 20x = 20 * 150 kB/s = 3.0 MB/s. The following table lists some common ratings and their respective maximum transfer rates.


Rating = Speed (MB/s)
6x = 0.9 MB/sec
8X = 1.2 MB/sec
12X = 1.8 MB/sec
20X = 3.0 MB/sec
25X = 3.8 MB/sec
30X = 4.5 MB/sec
32x = 4.8 MB/sec
40x = 6.0 MB/sec
60X = 9.0 MB/sec
66x = 10.0 MB/sec
80X = 12.0 MB/sec
90X = 13.5 MB/sec
100x = 15.0 MB/sec
133x = 20.0 MB/sec
150x = 22.5 MB/sec
200x = 30.0 MB/sec
266x = 40.0 MB/sec
280x = 42.0 MB/sec
300x = 45.0 MB/sec
433x = 65.0 MB/sec
600x = 90.0 MB/sec
666x = 100.0 MB/sec
For Video, Canon recommends at least 8MB/sec. Since all cards do not necessarily perform at their indicated speed, it is recommended to get a faster card. A 133x would be both safe and cheap. The money you are saving by not buying a more expensive cards, would be well spend getting a higher capacity card.
Hi Ed,
I am by no means an expert on video formats and compressions but I don't think you can translate the 'photographic settings' to 'video settings'. Video cameras, in general, use codecs that compress image sequences, so in fact when you have let's say a 30fps movie, the camera does not literally store 30 frames at 1920*1080 but determines a number of keyframes and uses interpolation algorithms between those keyframes. I think, but don't quote me on that, that the number of keyframes stored is closer to 4. Since all the calculations are done by the camera's processor, the actual writing speed can be much slower. So yes, 8MB is actually enough. I have a x133 card and haven't experienced any issue so far. The 7D has a buffer indicator that only appears if the camera can't write fast enough to the card. I have only seen that indicator once and at its lowest level and only for a second or two. So a x133 works absolutely fine. I picked x133 because it was slightly more than the double of the recommended 8MB/s because you have to account to different qualities in the cards. In my experience anything better than 20MB/s is more than enough for video and it is much more useful to invest in more capacity rather than speed. I hope that helps

yaoayao

一看月亮就知道7弟厉害！#10

moonbay

一看月亮就知道7弟厉害！#10
yaoayao 发表于 2010-9-1 07:25

遥遥！

袜贩

按您的意思，俺就不必劳神了？

这是网上找的资料。他们说的是用妻弟录像多少速度的卡足够快。

...
moonbay 发表于 2010-9-1 07:15

录像是另一回事了。因为拍录像可能要连拍很多分钟，机器没有时间和容量去buffer那么大的数据，所以存取速度是需要的。但连拍照片，你一般也就连拍1，2秒，十来张。7D绝对可以容下这个数，然后等你停下来，它还接着存。

moonbay

录像是另一回事了。因为拍录像可能要连拍很多分钟，机器没有时间和容量去buffer那么大的数据，所以存取速 ...
袜贩 发表于 2010-9-1 07:55

说的对，好镜头1-2秒钟足够了。