GH3 GH4; 4k SD card requirements?

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dalemccl

Member
I am excited about the prospect for 4k video with the GH4, but one thing that concerns me is the memory card requirements. Am I correct about the following?

1. 4k at 100Mb/s will require UHS-1 Class 3 cards that cost $300+ for a 64GB card?

2. These cards will hold approximately 1 hour of 4k video. Buying two cards to hold 2 hours of video will cost over $600, which is about a 1/3 of the price of the GH body's expected price.

3. Because the card's capacity is only 1 hour of 4k video, shooting an event (such as a stage play) that is longer than an hour will require changing cards during the show (and hope there is an intermission to allow time to make the change.)


Are my concerns legitimate or am I misunderstanding something?
 
My calculations tell me that a 64gb card should hold approximately 85 minutes of 100mbps video.
 
Those are real concerns, however you could probably just shoot the play in 1080. If you needed 4K for the production hopefully there are 4K recorders around the corner that are cheaper than the 7Q that also take SSD's. That would allow you to record a whole show without changing media while shooting 4k.
 
Thanks for the replies.

>>My calculations tell me that a 64gb card should hold approximately 85 minutes of 100mbps video.<<
I thought I read somewhere that a 32MB card will hold 29 minutes, so that is how I came up with about an hour on a 64GB card. I may have misread it. I hope you are right. 85 minutes would cover most school stage events I shoot.


>>Those are real concerns, however you could probably just shoot the play in 1080..... hopefully there are 4K recorders around the corner<<
My main reason for wanting to shoot in 4k is to allow zooming in post and still retain full resolution when rendering to 1080p. I'm not very interested in an external recorder because of wanting to keep the rig small. Good suggestion though.
 
dalemccl said:
Thanks for the replies.

>>My calculations tell me that a 64gb card should hold approximately 85 minutes of 100mbps video.<<
I thought I read somewhere that a 32MB card will hold 29 minutes, so that is how I came up with about an hour on a 64GB card. I may have misread it. I hope you are right. 85 minutes would cover most school stage events I shoot.
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I just did the math. 100mbps / 8 = 12.5 megabytes per second. 64,000 MB / 12.5 MB per second = 5120 seconds = 85 minutes or so.

I can confirm that I get 40-50 minutes or so with the 100mbps GH2 patches with a 32GB card.
 
DBP said:
I just did the math. 100mbps / 8 = 12.5 megabytes per second. 64,000 MB / 12.5 MB per second = 5120 seconds = 85 minutes or so.

I can confirm that I get 40-50 minutes or so with the 100mbps GH2 patches with a 32GB card.
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Thanks, that's encouraging. I would still probably buy 2 cards for $600+ (ouch!), but that eliminates the need to change cards while shooting a long event (as long as it isn't over 85 minutes.)
 
The Dingo,
The link you posted links back to this thread, but a search for the Sandisk UHS-II card finds it in Sandisk's webstore for $299.99. Perhaps the $245 price you mentioned is a discounted price at a web retailer? My searching didn't find it anywhere but at Sandisk. Where did you find it for the lower price? Thanks.

aldolega,
is that $110 card fast enough for 100Mb/sec? As I understand it, the speed typically claimed by card manufacturers is a burst speed that can't be sustained while writing long files like video. The sustained write speed is much lower. See below for Panasonic's statement of the required card type for 100 Mb/s 4k.

Footnote in the Panasonic GH press release:

*2 — Use SDXC/SDHC Memory Card compatible with UHS Speed Class 3 (U3) when using high bitrate video recording mode over 100 Mbps.
 
http://www.amazon.com/gp/aw/d/B00I3...ile?colid=3GAGRWZRDL55J&coliid=I32GI30ORADTZ8

It's UHS Class 3 so it should be fine. It'll probably be even cheaper by the time the camera comes out, too.

With speeds of 90MB/s read and 80MB/s write, it reads up to 9x faster and writes up to 8x faster than standard Class 10 SD cards. It meets the SD Association's latest specification release, UHS-I U3 (Ultra High-Speed Bus, Speed Class 3), which guarantees performance of at least 30MB/s and enough bandwidth to record and playback 4K2K video without interruption. Users can capture cinema-quality Full HD (1080p), Ultra HD (2160p), 3D and 4K2K videos on high-performance cameras
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Stu Siegal said:
Eduardo Angel, says "Shoot*ing 4K @100mb/s 30p on a 64GB card will give you about 29 min*utes of shoot*ing time." Eduardo shot with the camera, and talks about storage here.

http://www.eduardoangel.com/2014/02/13/7-things-we-discovered-after-shooting-4k-with-the-gh4/
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Thanks for the link. I was thinking it was 32GB cards that hold 29 minutes, but obviously I was remembering wrong. Hopefully, 128 GB cards will appear soon that are capable of holding close to an hour of 4K video.
 
Since everyone's favorite 64 GB SanDisk Extreme Pro UHS-1 card works just fine at bitrates up to 150 Mb/s, I have to wonder if it would also work fine for the 4K at 100 Mb/s. Hell, even the 128 GB Extreme (not Pro) card works just fine with Moon Trial 7 at 150 Mb/s. Spans and everything.

I think many of us who already own these cards will be testing before we buy any new UHS-3 card.
 
100mbps is 12.5MB/s. The UHS-1 class 1 is only guaranteed to sustain 10MB/s. Sure it can do faster but it does run the risk of crashing if you use slower cards. I believe the hacks on the GH2 are all variable bitrate so even if you use a 150mbps hack chances are most of your shots are not at 150mbps. On average they are probably much lower bitrate and only peak higher at specific moments. I used to use the 100mbps Flowmotion on my GH2 and my shots would hardly ever go above 50mbps.

We don't know how the GH4 handles the bitrate yet but it could be designed to take larger advantage of more of a constant bitrate peak. Since the video is 4k it may use a lot more of that 100mbps on average which means you may run the risk of crashing more often with slower cards. Remember 4k is 4x larger than HD so if we use the same bitrate ratio 100mbps at 4k could be like HD at 25mbps. It isn't exactly like that but the point is 4k may end up using a larger portion of that 100mbps 100% of the time which means the cards need to be pumping data at a pretty high constant rate and not just occasional peaks or bursts.

UHS-1 class3 has enough minimum guaranteed bandwidth to handles 4k at a constant 100mbps.
 
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Thomas Smet said:
I believe the hacks on the GH2 are all variable bitrate so even if you use a 150mbps hack chances are most of your shots are not at 150mbps.
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All I-Frame hacks record at a constant recording rate, so a 150 Mbps All I-Frame hack is a constant 150 Mbps recording rate for EVERY frame you shoot, which is why you have to use the Sandisk 95MB/sec SDXC cards to shoot with these high bit rate hacks.
 
Good to know there is no recording limit. It seems like to get 4K we are going to have to go with the Micro P2 cards or the new Sandisk's that are slightly cheaper. That is until Blackmagic comes out with a 4K version of there hyperdeck!
 
Dafilman21 said:
Good to know there is no recording limit. It seems like to get 4K we are going to have to go with the Micro P2 cards or the new Sandisk's that are slightly cheaper. That is until Blackmagic comes out with a 4K version of there hyperdeck!
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Which would be even more expensive and I believe requires SSD drives. Not a cheap route at all and completely dwarfs the cost of shooting to the expensive SDHC cards.
 
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