Video Recording Speeds and SD Card Speeds

"b" is for "bit". "B" is for "byte". "m" is for "milli". "M" is for "mega".

In other words, the camcorder records at 24Mbps which equals 3MBps. SDHC cards are rated in MB not Mb. Class 4 is 4MBps or more. Thus, a properly rated/performing class 4 card is more than enough.


SDHC Speed Link

Just don't tell Canon as they reccomend at least a Class 6 card for the HF G10/XA10 models.

I am too lazy to search through Canon's operating manual, but older models were fine with Class 4, and the Panasonic camcorders that record at 28 Mbit/s or more are fine with Class 4 too.

I tried putting Class 2 into the HF100, and was informed that high quality recording would not be possible on that card.

Usually the extra security especially if your getting paid to shoot something or faster download speed. Still, some cards are better than other. Class 10 cards are getting cheap anyway.

A hacked GH1 for example definitely needs a class 10 card if you set the bit rate high and ironically, their is a bit rate limit even for class 10 cards.

If the GH2's bit rate gets hacked, you'll wish it was a class 10 card that you bought.

I spoke with them on the phone and they told me Class 6 and above.
My house is all pulled apart reorganizing so it will be a while before I can dig out the manual.
I just go with Class 10 in a few years Class 10 will be slow anyway.

The only thing the online monkeys are good for is providing you with RMA number.

Sad, but true.

That's funny because in the M41 manual they recommend class 4. And it's the same sensor, lmao. maybe they think money doesn't matter to you guys.

Honestly, IMO, I think most people recommend class 10 because they get MB and Mb confused.

Buy what you need. When something faster is needed that card will be a lot cheaper. Besides I'd rather have two class 6 32GB cards than one class 10 32GB card.

When you get your SDHC card, download a free speed test program and test it. If it's not running at its rated speed, send it back. Test it before you use it then test it again before your return period is up if you're worried.

my class 6 tested faster than class 10 speeds.

* Class 10 cards may have the same actual speed as Class 6 or Class 4 cards.
* Class 10 cards may cost the same as Class 6 or Class 4 cards.
* Many camcorders verify card's class and do not allow recording if the class is not correct. But they can do it wrong. They can require class to be higher or equal then needed, like Class 4 or higher. This is the correct way. Or they can check for a particular classes known when the camcorder was produced, like Class 4 and Class 6 are ok, other are not. This is what the HF100 is doing, it can read Class 10 card, but it does not accept it for high-bitrate recording because it is not Class 6 and as such is "too slow".
* Some older camcorders do not accept Class 10 cards. Some of them can be upgraded via firmware update.

Lots of variables.

Which class 6 card and which class 10 cards were compared?

I just bought a SanDisk Extreme Pro UHS-1 SD card. It's rated at 95MB/s read/write and rated as a Class 10 card. I put it in the HF100 and the camera says it can't write in FXP mode. As Ungermann points out, it's checking the class incorrectly...

It would seem to me that video compression may or may not reduce video file size very considerably. ? If the video is of a small object that is moving in an unchanging background scene then the file size could be much smaller. But if the camera is panning rapidly the video compression could not reduce the file size nearly as much. Wouldn't the required SD card speed be different for each scene? That would explain why slow 2GB cards seem to work fine for my high speed video applications at 240 fps, Casio data rate spec 50 Mb/sec, while many people insist that very high speed cards are necessary for their applications. The manufacturers would spec fast SD cards for the least video compression and the greatest data rate. ?

FYI - My reply posted in dpreview Digital Video Forum

"Not very knowledgeable myself but it was explained to me that video compression often involves saving, first, one reference frame and then just saving the differences between that reference frame and each of the next X frames, say, for example the next 30 frames. After X frames a new reference frame is saved again and the process is repeated. With that compression logic scenes with stable backgrounds and a small moving subject might be very compressed while rapidly changing scenes would be less compressible. For your application on a moving vehicle it would seem that compression would not be near the maximum.

H264 is an often used video compression specification.

http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC

Discussion including the compression issue of frame number.

http://www.militaryaerospace.com/......-standard.html "

Manufacturers usually provide the lowest speed they guarantee, but a particular card can be (and usually is) faster. The encoder ensures than bitrate does not get higher than specified for a particular recording mode. Some cameras verify the speed class and reject a card outright if it has lower speed class than required for a particular recording mode.

I was reading Wikipedia about SD cards and there was the suggestion that "UHS" cards are a newer, faster standard. But, they may require "handshaking" with "equipment" (such as camcorders) to verify they are designed to work with each other.

In other words, the current crop of camcorders typically discussed on this forum may not do well with "UHS" cards. With Class 10 32GB cards hovering around $40, who can complain? Does anybody remember how much film and processing cost?

Bill