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Old 11-03-2011, 09:11 AM
 
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Quote:
Originally Posted by EinsteinsGhost View Post
I doubt the difference would be noticeable and it surely isn't.

There some variable there, the codec for starters. I've been out of the loop for a while so I couldn't tell you what was better.

As far as the resolution and the bitrates go if you wanted to put this in the context of images surely the difference between an image printed from a highly compressed .jpg at 150 dpi is no different than a high quality image printed at 300 dpi when viewed from 15 feet either.

You're camera can create images far beyond what most displays or even prints require but I bet you still shoot most images you want to keep using the highest setting possible? Why wouldn't you apply that to video which still has more practical potential than images since you're dealing with much lower resolutions?

If you have a large screen TV the next time a football game is on get up close, you're going to see all kinds of macroblocking. This is result of highly compressed video, you won't see that during an action scene when watching blu ray because blu ray uses a very high bitrate.
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Old 11-03-2011, 09:25 AM
 
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So Coalman, your posts seem to indicate that DSLRs adjust their video quality based on the speed of the card being used. Do you know for a fact that this is true?
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Old 11-03-2011, 09:42 AM
 
Location: Dallas, TX
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Quote:
Originally Posted by thecoalman View Post
You're camera can create images far beyond what most displays or even prints require but I bet you still shoot most images you want to keep using the highest setting possible? Why wouldn't you apply that to video which still has more practical potential than images since you're dealing with much lower resolutions?
Choice of resolution depends on a variety of factors. This applies to photos as well as videos. In video, my camera offers three settings:
AVCHD - Full HD (1920x1080p) which records at an average 17 MB/s
MP4/HD - (1440x1080p), records at an average 12 MB/s
MP4/VGA - Records at an average 3 MB/s

Recording isn't just between the card and the camera either. The camera has a buffer. If the recordings aren't extraordinarily long, I don't see the possibility of perceptible difference in speed between average and better Class 10 cards. I haven't. Of course, if I were to pick by default, it would be SanDisk Ultra III 16 GB/Class 10 which I have, with max rate of 30 MB/s, or Sony Memory Duo-Pro HG (also 30 MB/s). But I have also used Lexar with rated 15 MB/s max and haven't had any issue.
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Old 11-03-2011, 10:27 AM
 
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Quote:
Originally Posted by EinsteinsGhost View Post
Choice of resolution depends on a variety of factors. This applies to photos as well as videos. In video, my camera offers three settings:
AVCHD - Full HD (1920x1080p) which records at an average 17 MB/s
That's interesting. The spec for my Canon 7D shooting the same format is 5.5 MB/s. The manual recommends using a card with a read/write speed of 8 MB/s or faster. That explains why I haven't had any any problems even with my older CF cards, none of which are under 15 MB/s.

Also, I just learned that the 7D has a display that pops up to show you the depth of the buffer if it starts to fill up. That's pretty neat.

If the buffer does fill up, the recording stalls until the buffer empties out. The video transfer rate itself doesn't change, so the video quality won't degrade, but you will miss frames.
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Old 11-04-2011, 05:06 AM
 
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Quote:
Originally Posted by kdog View Post
So Coalman, your posts seem to indicate that DSLRs adjust their video quality based on the speed of the card being used. Do you know for a fact that this is true?
I don't own a DSLR, just know a lot about video. It's been a hobby and semi professional thing I've done for quite some time. I'd imagine it's manual setting and if the transfer rate wasn't fast enough it wouldn't be available but that's just a guess, you'd have to check the manual to see what each one does.

This topic used to come a lot when DVD burners came on the scene and mini DV was still the standard format. People were taking DV and compressing it into MPEG2 which is what is used on DVD discs. DV while compressed for all intents and purposes is uncompressed. Once they had it converted to MPEG they would get rid of the original DV, to the eye there might not be that much of a difference but there is substantial compromise of the video. I often equated it to throwing away negatives. For future use you're going to want the highest quality video you can have, here's a simple example I created years ago to show the effects re-compressing can have and works well because the lights are moving very fast. Note it's .jpg image so it's not exactly scientific.

This is screen shot from DV:



This is when it's been encoded to 8000kbps, not the edges of the light have some really minor macroblocking. This would be hard to notice even if you had both videos palying side by side:



If we take that 8000kbps video and then encode it to 3000kbps this is the results. Note that is far too low a bitrate for this resolution but the intention is to produce macroblocks.




Compare that to a video DV straight to the 3000kbps, we still have macroblocking but it's substantially less:



In the future as displays improve and the tech improves for scaling video up you're going to want the best source possible to utilize the increased resolutions. That means using a high data rate and high resolutions.
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Old 11-04-2011, 05:09 AM
 
41,815 posts, read 50,926,180 times
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Quote:
Originally Posted by EinsteinsGhost View Post
Choice of resolution depends on a variety of factors.
For me I always record video or take pictures at their maximum, I can always make them smaller. The only time I might consider reducing the quality is if space was concern. Never really ran into that problem.
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Old 11-04-2011, 05:16 AM
 
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Quote:
Originally Posted by kdog View Post
If the buffer does fill up, the recording stalls until the buffer empties out. The video transfer rate itself doesn't change, so the video quality won't degrade, but you will miss frames.
There's similar issue with USB2 and why the standard for tape camcorders is firewire to transfer to the computer. Becsue it's tape the transfer needs to be done real time and while USB2 has a faster data rate it also has a higher overhead which could possibly interrupt the transfer and you'll drop frames. Not such an issue now but it was years ago.
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