Compact Flash card for 7D

[Marvin]

<p>Burst mode in my Canon 7D is usually 8 fps. I often shoot at 1/1600th sec, eg, horse racing, dog racing. What specifications should I be looking for in a Compact Flash card?</p>

[wayne_woodruff]

<p>A little dated, but very informative <a href="http://robgalbraith.com/bins/content_page.asp?cid=7-10044-10297">http://robgalbraith.com/bins/content_page.asp?cid=7-10044-10297</a></p>

[michael.gregory]

<p>Marvin,<br>

I had this same question a few months ago and after quite a bit of exchange on this forum and some research on my own it is my opinion that if you need to capture bursts of action you should opt for the fastest transfer rate card you can get. Now here come the caveats. What the fast card buys you is recovery time. The famous buffer that is so much talked about is between the sensor and the dual processors. In burst mode depending heavily on the capture capture format, (raw vs jpeg) it will fill up in a certain period of time which is a function of how fast the processors can ship the finished files off to the CF card. It seems that JPEGs process and ship faster than Raw files so your bursts at 8fps will be longer before the buffer fills up. (Remember it is draining out at one end while filling from the other and the faster it drains the slower it fills). When the buffer is full it will send a signal to the processor stopping the capture of images until there is room in the buffer for them. That is when an image, (actually 2), have been shipped out of the processors and in to the CF card. In raw mode you get about 2.5 to 3 seconds of high speed burst before the processors, (the drain), can not keep up with the shutter, (the spigot).<br>

Here is the real kicker. If you are shooting jpegs with a really fast CF card You can process about as fast as you can shoot and you get much MUCH longer bursts. Either way what the fast cf card buys you is that it removes a potential bottle neck downstream of the processor. How important that is depends as much if not more on whether you need raw files or can do with jpegs and how long a burst you need. In general though, best practice to cover all the bases dictates getting at least two of the biggest fastest cards you can afford.If the action you need to capture takes longer than three seconds think seriously about shooting jpeg. If Image quality is paramount and the action takes longer than three seconds ... good luck.</p>

[steve_dunn2]

<p>Even with the slowest card, the camera will shoot at full speed until its buffer fills up. As mentioned in the detailed response above, this is where a faster card helps: the buffer drains more quickly, so you have room for your next burst sooner (or you can keep shooting at a higher rate than you could with a slower card). A faster card also speeds up chimping, and (assuming your card reader is fast enough) makes it quicker to download the images to your computer, which are both nice, but usually if you <em>need</em> speed, it's for shooting, not chimping or downloading.</p>

 

<p>So the main question is how long can you wait for the camera to flush its buffer between bursts? If you need to be able to shoot a burst and then be ready for the next burst almost immediately, you probably need to spend the money to get one of the fastest cards you can find. If you have more time between bursts, on the other hand, you can step down to a card whose speed is decent but not blazing.</p>

 

<p>An example of the latter, from my own personal experience (since I have no dog or horse racing experience to share): shooting planes flying by at an air show. A plane flies by, you shoot a burst, and then it takes a while for the plane to turn around at the end of its run before it comes back for its next run.</p>

[randallfarhy]

<p>With all of the info above taken into account, when I'm shooting race car sequences I make sure that I have at least a 60MB/s card installed. I shoot RAW or RAW +Jpeg and rarely have the buffer lock up to the point it stops the camera from shooting (22 frame accident sequence is the longest so far). It does start to slow a little at around frame 15 but doesn't lock me out, and clears fairly quickly. I do notice in much lower light it doesn't shoot as fast as the 8fps max, more like 6. </p>

[mark_poseley]

<p>If you shoot RAW your file size is what, about 21 MB or so with the embedded jpeg? If so, 21 Mb at 8 fps is 168 MB/s. So, the fastest card you can get will keep you shooting longer before the buffer fills and slows you down.</p>

<p>If you shoot jpg only, as noted above you can get by with a slower card since file size is greatly reduced.</p>

<p>As a comparison, I have a 5D MKII and a 30 MB/s card. I can get about 8 - 9 frames at full speed shooting RAW + jpg (roughly 30 MB of data per shot) before the buffer fills and frame rate slows to a crawl. My friend w/ 90 MB/s cards does much better.</p>

[pjmeade]

<p>I find the 60 MB/s Sandisk 16G cards ideal for shooting polo with the 7D.<br>

hope that helps.</p>

[Marvin]

<p>I called Canon. They said that with the 7D there is no particular card speed that is required when shooting at high shutter speeds. Other cameras eg., Nikon does require a high speed card but not Canon.</p>