Canon 6d SDHC card write speed

[proust]

<p>I recently bought a Canon 6D and a Sandisk 16GB SDHC class 4 card. Comparing it to a 7D + a CF card (which is my previous camera), the write speed for a RAW image with the 6D is much slower than the 7D - it takes almost 2 seconds for it to be written and the red light blinks for another ~2 seconds before clearing.<br>

Is it the card or the camera or is this expected? <br>

Thanks.</p>

[Spearhead]

<p>Class 4 is very slow. However, unless you're filling your buffer, this shouldn't matter. The CF card you used could also be a factor.</p>

[proust]

<p>How would I know if the buffer is being filled? Also, I'm a little confused when you say that the CF card could be a factor - the CF was on the 7D which had fast write speeds; the 6D has the SDHC.</p>

[Spearhead]

<p>SDHC refers to the size, not the speed. Class 4 is the speed indicator. If you buy a Class 10 card, it will be faster. If you buy a UHS-1 card, it should be a lot faster. However, this doesn't matter if you are not filling the buffer shooting stills. Until you fill the buffer, the card speed is irrelevant.</p>

<p>You can tell if the buffer is full if you can't shoot any more. The buffer holds around 17 RAW shots on a 6D.</p>

[Andrew Garrard]

<blockquote>it takes almost 2 seconds for it to be written and the red light blinks for another ~2 seconds before clearing.</blockquote>

 

<p>Just to be clear... It's been a while since I used a Canon, but I would expect the light to blink while data is being written to the card. What do you mean "two seconds to be written, then two more seconds of light blinking"? Is the camera not responding for the first two seconds?<br />

<br />

As Jeff said, the 6D should be able to shoot a number of shots to its internal buffer while letting you continue to use it - this should empty to the SD card in its own time, and shouldn't interfere with your shooting unless you take enough shots to fill the buffer. If you're seeing a pause and you've not taken a lot of shots in rapid succession, something else is going on.<br />

<br />

Pedantically, SDHC is a variation on the specification to allow different sizes. There are devices that support SD but not SDHC. The latest variant is SDXC. UHS is a protocol that's part of the SD specification (allowing higher speed transfers; UHS-I uses the same form-factor as normal SD, but UHS-II uses extra connections). Class is, as Jeff says, about speed - either a number in a circle for approximate sustained number of MB/s (bigger is better) or a number in a "U" for UHS - U1 can read/write at least 10MB/s and U3 can write at least 30MB/s. Class 4 <i>is</i> slow compared with the current state of the art, and the camera can make use of faster. But this should affect how quickly the buffer empties, and be irrelevant unless you fill the buffer. (It may also affect image review times, but I assume that's not what you're doing.)</p>

[proust]

<p>Thanks for your replies. I don't think I'm filling the buffer as I'm not taking a series of back-to-back photos but just one photo at a time.<br>

Andrew - it takes about 2 seconds after I press the shutter for the image to be displayed on the LCD. And after that, it's about 2 more seconds before the busy red light stops blinking. During these 2 seconds, I can't do things like delete the image or scroll back in the series of previous images.<br>

It's not a huge problem unless it's a sign of something else that's broken. This is a new camera (1 week old) and I'm still within the 30-day return policy. If this is common to all 6D + SDHCs shooting 1 image at a time, I'm not too concerned but if it's not, then I might be inclined to return it...</p>

[Andrew Garrard]

<p>Hi John. Thanks for elaborating. I've no experience myself of the 6D (beyond playing with one), but dpreview say:</p>

 

<blockquote>Image browsing and magnification in playback mode is very swift as well.</blockquote>

 

<p>It's possible that the camera is insisting on writing the image before letting you review it (can anyone confirm?) - in which case, a UHS-1 card might help you. I doubt it's a defect with your particular camera, though I can't vouch for the 6D's behaviour in general. I can't say I normally have review turned on when shooting - it kills the battery! I hope a 6D owner can chime in for you - good luck.</p>