Effects of SDHC Card speed on GH1

N

noirist

Well-known member
Since getting my GH1, I've been curious to know what benefits faster SD/SDHC cards provide. So last week I broke down and got a $149 Photofast Dual Channel 32GB Class 10 SDHC to conduct some testing. I chose the Photofast because that company made the fastest Compact Flash cards in Rob Galbraith's test, because it was available in 32GB, and because it wasn't that much more expensive than the $115 Transcend 32GB Class 6 SDHC card. I compared the Photofast to an old Sandisk 2GB Class 1 SD card (currently available for $8) and a new Transcend 16GB Class 6 SDHC (currently available for $38).

For my first test, I put the GH1 on full auto and shot as many RAW images as possible within two minutes. The Sandisk Class 1 shot 41 images, the Transcend Class 6 shot 59 images and the Photofast Class 10 shot 55 images. While this is a reasonable test of camera write speed, it is not a useful or practical metric because I certainly wouldn't use the GH1 on full auto past the initial 5 RAW image burst. So my principle conclusion from this test is that a faster card may increase the number of full auto bursts that you can shoot, it doesn't increase the number of images in a full auto burst.

Next I shot 1080p24 onto the Sandisk Class 1 to see if it was even possible. It was. I shot 5 minutes waving the camera around to saturate the codec without any problem before stopping.

So my first conclusion is that faster cards don't provide any practical benefit on the GH1. And my second conclusion is that the SDHC Class ratings don't mean much because a class 6 card can be faster than a class 10 card. And thirdly, I'd recommend getting the $115 Transcend 32GB Class 6 card instead of the $149 Photofast 32GB Class 10 card.

07/18/2010 Update - I started testing the cards with HD_Speed, see http://www.dvxuser.com/V6/showthread.php?t=217260
 
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Damn that's dissapointing but pretty much backs up my own experience with the fast cards and the GH1's video mode. It makes not a bit of difference.
 
Did you test/notice any difference in transfer speed of each card? Assuming you have a card reader, it would be nice to know how much faster a Class10 card transfers than a Class6 and so on.
 
I thought as much for the GH1 video write speed needs. I'm thinking that the max rate being 17mbps, that translates to 17mb divided by 8 (8 bits in 1 byte), which turns out to 2.125 MBytes per second.

I'm thinking that's the least write speed you need to be able to record video unto the SD card. So technically a "good" SD card classified as class 2 (didn't know class 1 existed) should work, because class 2 should have a minimum speed is 2MB/s.

Yes, the camera can write faster, but that doesn't mean it will use faster writing as the camera might only be outputting 17mbps unto the card. That's what I'm thinking.
 
You have to fill the card to be sure - speed varies end to end. Have you tried the "CardTest" utility that I've linked to before?
 
This thread should be a sticky. Seriously. Can we stop speculating about the possible effects of card speed on codec performance now?
 
So if I'm reading it correctly... I should be Ok with a class 2 card ? I always thought that I'll need Class 6 or better to make the most of Gh1 video capabilities.
 
Barry_Green said:
It requires a Class 4 card to handle 17mbps. The owner's manual recommends a Class 6 card.
Click to expand...

It seems as if "class" could be a bit deceiving. Perhaps a suggested minimum speed. I saw a recent GH1 brochure suggested over 10mb/s (which could be class 2).

I bought a sandisk ultra2 16gb (15mb/s class 4) after standing in the aisle for half an hour deciding.... lucky I dont charge clients at an hourly rate.
 
I have a class 6 card made by "Patriot" and it was too slow to be used in GH1 for 720/60, as the camera will display the message saying that the card is too slow. Switch to SanDisk class 6 and it works well. By comparing the speed of shooting RAW, the SanDisk seems to be faster by just a little bit. Thus while the speed and the brand of a card may not matter that much for shooting still, they may make a big difference if you plan to shoot video at HD.
 
Interesting findings, it falls in line with my unscientific testing of the GH1. I purchased a Patriot LX 16GB Class 10 card for the cam. I did some testing with Crystal Mark to determine the speed of the card. I was let down to find the card did 3.5 MBp/s in my SD Card reader. It however did 14+ MB/s on the sequential read test.

I then thought maybe I should test the speed of the card with the GH1 connected via USB in USB mode.

That test was even more odd. Turns out I was only able to must 5.5MB/s read but did bump up write performance to 4.1 MB/s. I wonder if this problem is due to the card itself, or a combo of the card and camera.

Would be interesting to see others experiences with SDHC cards.

Mike
 
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