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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old June 3rd, 2010, 01:47 AM   #1
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7D Recording Time Can Vary Above 12 Minute Length

Yesterday we shot some interviews, and some of our shots was as long as 19 minutes in 1920 25p. The subjekts was filmed against a black background. I guess this is because the H.264 codec can compress more frames into the 4GB file size limit due to the black background and relatively low degree of motion.

Does anyone else have similar experience?
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Old June 3rd, 2010, 07:06 AM   #2
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This is an interesting point and I believe it is true. I have not tried to do a long take, but I do shoot product scenes on a white background and the file sizes can be less than a quarter the size of a regular outdoors scene of the same length.
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Old June 3rd, 2010, 08:57 AM   #3
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The same thing happened to me for the same reason. A couple of weeks ago I was part of a team shooting a live performance. On the wider shots there was lots of black background. Some clips reached 16 minutes long.
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Old June 3rd, 2010, 01:01 PM   #4
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Wow! Talk about a misleading thread title! This is not an "override" of the file size limit.

H.264 is a variable bit rate codec. "Complex" images are relatively less compressed, while "Simple" images are more highly compressed. The upshot is as you describe - variability in the running time of a 4GB clip. However, the general rule of thumb still applies - 12 - 13 minutes per 4GB clip for most "real world" shooting situations.
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Old June 3rd, 2010, 03:48 PM   #5
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Quote:
Originally Posted by Jeremy Pevar View Post
Wow! Talk about a misleading thread title! This is not an "override" of the file size limit.
Hmmm.... Where in the thread title do I mention file size limit?
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Old June 3rd, 2010, 07:57 PM   #6
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You are absolutely correct, you do not say "file size," but rather "recording time." My apologies.

My point, though, is that this isn't an "override." It merely describes the nature of the H.264 codec: the variable bit rate yields variable recording time for a given file size.

When I clicked on the thread I thought maybe someone had come up with an "override." I should have known better. I'm disappointed, that's all...
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Old June 3rd, 2010, 08:09 PM   #7
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Hey guys. Couldn't help but trip across this and as someone who acknowledges he himself can be pretty controversial at times, make I make a very polite suggestion;

Chris Hurd has gone out of his way to ensure that this is a place for all contributors to feel welcome. Could I respectfully suggest that Onar, being from Norway, probably doesn't speak English as a first language (although from what I see here, it's pretty darned good...). So if the word "override" isn't technically accurate, it might be more constructive to SUGGEST the title be changed instead of "poking fun" at it's inaccuracy. As well, exclamation points can be EASILY misunderstood as "shouting" and probably weren't the most DIPLOMATIC way of making a somewhat valid point.

Welcome to you both and may you continue to share and learn with us all.
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Old June 4th, 2010, 06:59 AM   #8
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I thought this post was very good, some people using the 7D might read the instruction book and see the 12min record time as total maximum time and never try to go over it. I find posts like this extremely helpful to shine a spotlight on a grey area of use and educate.
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Old June 4th, 2010, 01:26 PM   #9
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I will gladly change the thread title if any one have a good sugestion. :-)

I am sorry if the quotes were missunderstood. In norwegian we often use them to show that a word is used as a substitute in lack of a better word.

I started the thread because I find it interesting that there can be as much as seven minutes variation in recording time.
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Old June 5th, 2010, 01:13 AM   #10
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How about "7D Recording Time Can Vary Above 12 Minute Length"
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Old June 7th, 2010, 05:44 PM   #11
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Thanks, Jeremy, for your sugestion. How can I change it. I can't find an edit button....
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Old June 7th, 2010, 06:07 PM   #12
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You can't edit the title of the thread. But I can.

Changed from "12 minute limit override!" to " 7D Recording Time Can Vary Above 12 Minute Length"

In all honesty I thought we had established that the twelve minute
limit was *approximate* and that it can vary due to a number of
factors. There are also situations where you'll get less than 12
minutes before the 4GB limit is reached.

The camera stops recording when the file size reaches 4GB.
In SD video that's appx. 30 minutes. In HD video it's closer
to 12 minutes. Could be more, could be less. 12 minutes
is just a good rule of thumb. Sometimes you'll get more
than that. No big deal here.
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Old June 8th, 2010, 12:31 PM   #13
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Quote:
Originally Posted by Chris Hurd
The camera stops recording when the file size reaches 4GB.
In SD video that's appx. 30 minutes.
I believe that in SD it stops at 29:59, even if it hasn't reached the 4GB limit.
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