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Herman老師 wrote:
很多人應該是沒有遇過...(恕刪)
其實現在會考慮買到32GB卡的人, 很少是買他們有生以來的第一張CF卡, 應該很多人以前早就有4GB, 8GB, 或是16GB的了! 想買32GB, 無非是希望在拍攝當中可以一次拍多一些, 或是多錄一點時間, 以防錄到一半不夠, 還要換卡, 造成中斷.
所以出門多帶幾張卡以防其中一張卡出狀況這我絕對是贊同的, 我個人也都會有備卡. 但備卡大可用你以往信賴度高的舊卡就可以了, 這些舊卡也至少有4GB或8GB的容量, 要當備卡綽綽有餘. 而要考慮買新卡時, 如果有需要, 32GB或64GB就買下去了, 何必還要考慮到把32GB卡拆成一半, 買16GB卡兩張? 我覺得大可不必. 如果真的是一張CF卡都沒有, 我也會建議樓主既然要買32GB卡就買下去, 然後再花一點點很少的錢買張8GB卡(現在很便宜)來當備卡. 而且買卡時品牌的信賴度非常重要, 我個人的經驗是, 一張Sandisk CF卡的信賴度要比兩張其他牌的卡來得還保險!
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我的 400x 搭 5D2 RAW, 也還會頓, 每秒3.5張,13張後開始約每秒1.5張
很好奇有沒有用 600x 的大大可分享在 5d2 or even 7D , 50D 上的連拍速度
PS: 純實驗數據分享, 甚麼夠用就好;連拍那麼快你又用不到等就不在這裡討論, thanks
jie1128 wrote:
就算我用的是 最慢的 2G SD CARD+SD轉CF卡 速度只有 3M/bps
依拍攝場景 還是可以7~9連拍 才停頓一下下
因為有的場景拍照所佔用的記憶體容量比較大 jpg可能就佔到14M 所以只能連拍七張最多
高低速卡的差別只在於 停拍之後的儲存時間長短
...(恕刪)
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8MB x 8=640Mbit
64Mbit /1.2Mbit ==> 53x
但實務上我的 A-Data 266x, 用在5D2 上連拍RAW, 寫入就是比Sandisk 400x "慢很多" 而非只慢0.5倍 (400x vs 266x), 更非下文所敘的沒差了, 另外寫入 video 到A-data 266x 時無故壞檔的恐怖經驗就更不用說了 ---> 有沒有可能 A-Data 266x 的標示是黑心不實的標示?
====轉貼================================
Canon 5D2 and Compact FlashBy pvdhamer
Monday January 19, 2009
UDMA
Canon stresses that you need a fancy, fast compact flash card to write data to the card as quickly as possible. The camera even supports a mode called UDMA Mode 6 which, according to Canon, is currently not even available yet on the market. The qualifier “UDMA” – regardless of the mode – is hardly used in the specifications of memory cards: manufacturers prefer to use terms like 20 MBytes/s and 200x (in units of 1.2 Mbit/s or 150 KByte/s after the 1x CD-ROM speed).
Need for Speed?
The point of fast cards is mainly that this allows a burst of images (4 frames/second) to be streamed to the compact flash card while the burst is taken. Thus the burst size would increase beyond the number of pictures that fit in the internal (SDRAM) buffer because that buffer is simultaneously emptied to Flash while it is being filled.
Leaky bucket model
If the memory card runs at p% of the speed of the data source, a simplified model predicts that the burst size increases by a factor of 1/(1-p/100) or 100/(100-p). This formula also apply to how much water you can pour into a “leaky bucket” until it is full: while you add 1 unit of water (data), p units have disappeared at the other end. For p=10%, the burst size becomes about 10% larger than for p=0 (an infinitely slow memory card, or non-leaking bucket). At p=100%, the internal buffer will never fill, meaning that the camera can write data to the memory card as fast as it is created. Your burst size is limited by the free space on the memory card.
Interestingly, Canon quotes the following disappointing improvements when you switch from a standard (8 MB/s) card to a very one: full RAW improvement 13→14 frames, sRAW1 15→15 frames, sRAW2: 20→20 frames. For JPEG the differences are quite significant: best quality 78→310. When the JPEG file size is reduced to 2 MB/image, faster memory cards give no improvement to burst length because a standard 8 MB/s memory card can keep up with the 8 MB/s (3.9 fps x 2 MB/frame) data rate.
Conclusions
The improvements you get with a fast memory card when taking still images appear to be minor (based on Canon’s data), and certainly less that would be the case if data could stream out of the SDRAM buffer at the bandwidth of the flash card. In general, it means that if you shoot RAW, you don’t need to buy a card that is much faster than 8 MB/s (53x) in order to increase burst size. And to support the 5 MByte/s video, you also don’t need more than an 8 MByte/s card.
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