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View Full Version : 7D Memory Card Data Rates - Whats the bare minimum for video?



shoot2ill
11-12-2009, 01:16 AM
Hey all,

I don't know if this has been discussed, I couldn't find anything in the search.

I'm getting a Canon 7D primarily to shoot video. My question is, what is the minimum speed CF card that will work well with video? People keep saying get UDMA and get 45MB/S or more.

BUT the data rate for 7D video seems to be around 45-48 megaBITS per second, which would be around 4.5 to 4.8 megaBYTES per second. Even if it was 5 or 10 MB/s, thats nowhere near 45 MB/S - 60 MB/s that people have recommended. Is my math wrong here? Are there other major reasons you want a fast card or UDMA for video?

Any help is greatly appreciated. Thanks!

lodus411
11-12-2009, 06:48 AM
I just bought this one and it works great. :)

http://microcenter.com/single_product_results.phtml?product_id=0313636

ydgmdlu
11-12-2009, 12:48 PM
Are there other major reasons you want a fast card or UDMA for video?
It'll help you sleep better at night (you know, before your shooting days).

UDMA is also Canon's official recommendation. Their engineers apparently experienced problems that didn't appear when they used UDMA cards.

Some people have speculated that faster cards offer better, more reliable buffering capabilities, which may or may not be essential for video recording.

But for the record, I and many others have used 133x cards without problems.

shoot2ill
11-12-2009, 08:36 PM
interesting...so you probably don't need it, but you could possibly run into some issues. tough call...I'll probably just end up getting the faster ones to be safe.

thanks guys!

ROCKMORE
11-30-2009, 03:19 PM
I just bought this one and it works great. :)

http://microcenter.com/single_product_results.phtml?product_id=0313636

You bought which card?

chris f
11-30-2009, 10:38 PM
Most people like the Kingston 133x cards, so that's what I bought and for the most part has worked perfectly fine, but I will say that during my last two extended shoots the card's buffer filled up and stopped recording during a take. Not a huge deal, but enough to have me thinking about getting a UDMA card for very important interview shoots.

ROCKMORE
11-30-2009, 11:32 PM
Most people like the Kingston 133x cards, so that's what I bought and for the most part has worked perfectly fine, but I will say that during my last two extended shoots the card's buffer filled up and stopped recording during a take. Not a huge deal, but enough to have me thinking about getting a UDMA card for very important interview shoots.

What is the speed of the Kingston 133x card?

What is the advantage of using a UDMA card?

wildfly
12-01-2009, 08:52 AM
I haven't had a problem with my Kingston 133x 32GB cards. I have very seldomly seen the buffer fill to two bars, which is still within acceptable range, and it will only do it for a second or two usually right after hitting record. I cannot, however, take a photo while recording video. It will fill the buffer and stop the recording, which then needs to be restarted.

ROCKMORE
12-02-2009, 06:20 PM
I haven't had a problem with my Kingston 133x 32GB cards. I have very seldomly seen the buffer fill to two bars, which is still within acceptable range, and it will only do it for a second or two usually right after hitting record. I cannot, however, take a photo while recording video. It will fill the buffer and stop the recording, which then needs to be restarted.

I looked up the Kingston 133x 32GB and it is only /
Speed** — 25MB/sec. read, 20MB/sec. write

If the 7D has a 45MB/ sec to 48MB/sec data rate off the sensor how does your 25MB/sec card keep up?

Wouldn't one of these perform better with the 7D?

http://www.bhphotovideo.com/images/images150x150/646870.jpghttp://www.bhphotovideo.com/images/images150x150/571877.jpgfile:///C:/Documents%20and%20Settings/Administrator/My%20Documents/CANON%207D/SANDISK%2045MBSEC.jpg

ydgmdlu
12-02-2009, 07:25 PM
No, the camera's bit rate is NOT 45-48 MB/s. It is 45-48 Mbps. That's a difference of a magnitude of eight. The bit rate in MB/s is only 5.5-6. You should read a little bit more carefully. :)

ROCKMORE
12-02-2009, 07:40 PM
No, the camera's bit rate is NOT 45-48 MB/s. It is 45-48 Mbps. That's a difference of a magnitude of eight. The bit rate in MB/s is only 5.5-6. You should read a little bit more carefully. :)

I'm still researching and don't have the camera or the card yet, so I'm still learning about them. Do you have a link for the explanation in detail, I'd like to study it more. Thanks

ydgmdlu
12-02-2009, 08:00 PM
MB/s is megabytes per second. Mbps is megabits per second. There are eight bits in a byte. That's how you get 6 MB/s from 48 Mbps.

ROCKMORE
12-02-2009, 08:14 PM
MB/s is megabytes per second. Mbps is megabits per second. There are eight bits in a byte. That's how you get 6 MB/s from 48 Mbps.

So what is the slowest speed card the camera can use at it's highest Mbps. output from the sensor to the card?

ydgmdlu
12-02-2009, 08:19 PM
So what is the slowest speed card the camera can use at it's highest Mbps. output from the sensor to the card?
A 66x card is theoretically good enough but not recommended. 133x cards offer the best value, I've found, at higher capacities (like 16 GB and 32 GB). Really, you should just buy the fastest card that you can afford, for peace of mind about buffer issues.

ROCKMORE
12-02-2009, 08:35 PM
A 66x card is theoretically good enough but not recommended. 133x cards offer the best value, I've found, at higher capacities (like 16 GB and 32 GB). Really, you should just buy the fastest card that you can afford, for peace of mind about buffer issues.

So the Sandisk Extreme 45MB/s is worth investing in.

ydgmdlu
12-02-2009, 09:00 PM
So the Sandisk Extreme 45MB/s is worth investing in.
If you think so. I don't mean that flippantly. I think that 133x cards are good enough, so I personally wouldn't buy a faster card. But I know that a lot of people would disagree with me. What is inarguable is that faster cards offer more peace of mind. Is the extra peace of mind worth the heavy price premium to you? Maybe it is. But for myself only, it's not.

massith
02-17-2010, 07:55 AM
If you look into the manual with the canon 7d ore the 5d MII you can see that there they say you need 8mb/sec. " When shooting movies at 1920x1080 size (Full HD quality), use a large-capacity card having an actual reading/writing speed of at least 8 MB/sec "

The company that Im working for just bought 2 of the 5d MII so Im going throug the manual about tips and tricks. So far I have only been using the standard RED cards that come with the RED ONE camera, but Im going to order some cards next week for the Canon 5D MII. I have been talking about getting smaller cards 4 - 8 gb at 45mb R/W and go to 60 ore 90 in bigger ones.

I have the 7d my self and for that one I have just been using the same cards as for the RED ONE.

Hope to see some comments on how the cards are working out for y-all

regards. Marzellius