Which UDMA cards are you getting?

Exactly. But for those that shoot non stop, even with 64GB cards you would want three. For me, right now, this 32GB will carry me through. But before I go up to Minnesota to scout I will get a second one. That way I know I can shoot non stop and dump into the laptop in the car. If you have a crew, rented gear, payed locations, etc... three is a wise idea, especially at these prices! It is like you say Sttratos, it depends. Nobody can tell you what you need other than yourself.
 
Certainly. But a 64GB is 192 minutes of 1080p. For drama single camera, this is a lot and way more than enough. How many productions out there shoot 192 minutes a day? Besides DV directors that just leave the camera rolling all the time hoping to catch a lucky moment from their amateur actors. LOL. But 192 minutes is 19 film magazines.
Now if what you do is ENG, weddings, documentary etc, then it's entirely different of course. Like we already said, highly depends.
 
Absolutely agree with owning more than one card. I wanted to give it a little time to test and myself some time to earn a little with the camera. Turn that around on three more cards.
 
You also want to consider more than one card in the off chance that one fails on you in the middle of a shoot. Yes it would suck to lose the footage/images on the one card, but it would suck worse if you only had one card period and had to stop for the day. At least with another card ready to go you could salvage the rest of the day. Does the phrase "Don't put all your eggs in one basket" ring a bell?
 
mhood said:
Anything over 5.5MB/s should be fast enough for video recording.
Click to expand...

Canon recommends 8Mb/s in their manual. Canon rep recommends nothing less than UDMA cards.

I guess if you're buying local then it's easy enough to return a card. I've ordered online, so I went with Extreme IV's just to be safe. I'd hate to lose some video due to dropouts.
 
Boz said:
Canon recommends 8Mb/s in their manual. Canon rep recommends nothing less than UDMA cards ... I'd hate to lose some video due to dropouts.
Click to expand...

I suspect (could be totally wrong) that the Canon rep is recommending UDMA for total functionality on the camera...shooting stills while recording video and blasting RAW still sequences. I don't know of a CF card out there anywhere that doesn't exceed 8Mb/s write speed. Of course, if I run into problems, I'll dump that 133x Kingston like a sack of rocks.
 
Here's the full quote from Tim Smith Canon Rep (in regards to 5D, though I would think the same applies to 7D):

"Is everybody here using UDMA cards, specifically UDMA cards when they get their compact flash cards? If you're not we're running into some real technical issues. It's showing some artifacting and some things that are not our fault. Stick with the UDMAs. A lot of the banding issues we were seeing on a lot of the shoots only showed up with the non-UDMA cards... ...What we think what happens is with the non-UDMA cards the camera can sense the speed of the card and it kind of dumbs down the data into the card which is causing some issues. It's our best guess at this point. But with UDMAs it's not an issue."

Also, Stu Maschwitz told me he only uses UDMA cards after having some video drop-outs when using non UDMAs.

So take it for what it's worth.
 
Boz said:
What we think what happens is with the non-UDMA cards the camera can sense the speed of the card and it kind of dumbs down the data into the card which is causing some issues.
Click to expand...

That's some real live voodoo right there for sure. We've been over this but I'd sure like to have that explained in layman's terms.

I figure the 133x will at least work for 640x480 capture (I'm a little ashamed to say that some of what I'll be doing will involve presentations headed for the Web as learning objects and VGA is fine for this) and should get me over 4 hours of record time on the 32GB card.

Again, if it fails me, I'll park my pickup truck on it.
 
Yeah, I can't imagine you having any trouble at 640x480. I'll be shooting 1920 and scaling down to 720 to do my post work.
 
'Photofast' have been getting some really good reviews on both price and performance, but availability is limited and customer support unknown.
 
Perry Wilson said:
can anyone elaborate on this ^
Click to expand...

It's covered on page 154 of the 7D Owner's Manual.

As I understand it, you just hit the shutter all the way while recording a "movie" and the 7D takes a still. It freezes the movie for about a second and the recording resumes automatically. I can't imagine why anyone would want to do this but the 7D supports it.

I also noticed that in the section on taking stills while in movie mode (page 154), they specify a UDMA CF Card 8MB/s or faster. At the begining of the the chapter (page 149), they speak only of a "large-capacity card having a read/write speed of at least 8MB/s." No mention of UDMA...

That (and the fact that I can't get my head wrapped around the "camera senses a slow card and adjusts the data rate" voodoo) is why I suspect the UDMA requirement is to accommodate the speed hungry features like RAW sequence capture and stills during movie recording.

 
mhood said:
That (and the fact that I can't get my head wrapped around the "camera senses a slow card and adjusts the data rate" voodoo)
Click to expand...
Why does this need to be voodoo?

Look at it this way -- the burst mode on the 7D is, what, 8fps? But if you hold the shutter speed down and keep going and going and going, doesn't it slow down to something like 2fps? Presumably there's a buffer in there that the camera stores the raw frames in, and the buffer goes to the memory card. If that buffer gets full, the camera has to slow down.

So -- apply the same idea to video -- it uses 47mbps as long as it can, until the internal RAM buffer is getting full. Then when it polls the buffer and sees that it's almost full, it decides "hmmm... maybe I should drop down to 35mbps for a while, until that buffer empties out some." Each group of 15 or 30 frames is processed entirely independently from every other group, so it's potentially possible that the camera could re-evaluate at the beginning of each group of frames to see how much bandwidth it should allocate.

Wasn't there something in the manual that says picture IQ could degrade on long-duration captures? Seems like the same thing could apply; the longer it goes, the more backed-up the buffer could get, and therefore the lower the bandwidth might go.

Same basic concept as buffer underrun protection when writing a CD or DVD, instead of writing directly to the disc you write into a buffer, and that buffer provides a layer of protection against hardware-induced delays causing you to burn a coaster.

Now, none of this is "known" or "factual", this is all speculation, but if there is any truth to the need for UDMA cards or glitching being caused by non-UDMA cards, then this is (what I feel to be) a reasonable explanation as to how the camera could "sense" the slower card and adjust the compression dynamically.

Could all be hogwash. But it's the first approach I'd take, if I was the compression engine designer.
 
mhood said:
It's covered on page 154 of the 7D Owner's Manual.

As I understand it, you just hit the shutter all the way while recording a "movie" and the 7D takes a still. It freezes the movie for about a second and the recording resumes automatically. I can't imagine why anyone would want to do this but the 7D supports it.

I also noticed that in the section on taking stills while in movie mode (page 154), they specify a UDMA CF Card 8MB/s or faster. At the begining of the the chapter (page 149), they speak only of a "large-capacity card having a read/write speed of at least 8MB/s." No mention of UDMA...

That (and the fact that I can't get my head wrapped around the "camera senses a slow card and adjusts the data rate" voodoo) is why I suspect the UDMA requirement is to accommodate the speed hungry features like RAW sequence capture and stills during movie recording.
Click to expand...
I wouldn't mind using this whilse shooting a wedding or something... I bought a 16 Extreme Pro 90mb/s so I should be good but does it stop the video when its uploaded or just on the cam?
 
Barry_Green said:
Wasn't there something in the manual that says picture IQ could degrade on long-duration captures?
Click to expand...

Best explanation I've seen so far, tyvm. IIRC, the bit in the manual about picture IQ degrading was speaking about the effects of heat buildup. If the buffer writes to a 5.5MB/s stream, how would it know if the maximum stream the card could write was 8MB/s or 60MB/s? I can see a cheap defective card that isn't performing to its specs might drop below the 5.5MB/s stream the buffer is expecting causing the buffer to build beyond capacity but I really don't see a 5.5MB/s stream being only available in USDM cards.

At any rate, if my Kingston 32GB 133x card lets me down, I will burn it in an elaborate ceremony involving chicken bones and beer.

Besides...This should be a dual card system. I should be able to use my SDHC Type 6 cards.
 
Last edited:
It doesn't know or care how fast the card is. The buffer's job is to write the next "sector". It tells the card to write, and asks it for confirmation that it's written. It then moves on to the next sector, etc. Assuming that there's some asynchronous handshake protocol in there, which I can't fathom that there wouldn't be...

So anyway, this theoretical buffer writes as absolutely fast as it can, limited only by the card's transfer speed. So the camera hands the buffer a new GoP every half a second, and the buffer writes out its contents to the card as fast as possible. In an ideal world the buffer would never even fill up because the buffer would be spewing data out to the card as fast as or faster than it was receiving it. But the whole point of having a buffer would be for the times when the card, for whatever reason, WASN'T fast enough. So instead of having a big hiccup or glitch in your footage (ever seen a dropout in HDV? It's horrible!) the system should have some sort of buffer in place on a tapeless system, to avoid that situation.

Again, this is total speculation from an ex-programmer. I could be completely wrong in all this; I just think it makes sense and I'd be very surprised if there wasn't some sort of protection to avoid dropped-GoP issues like happen on HDV tape.
 
You must log in or register to reply here.
Back
Top