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SDHC cards - Class 4 or 6, does it matter?

post #1 of 6
4/1/09 at 3:59pm
Thread Starter 
For normal photo-taking, does Class 6 help with burst mode only, or is Class 4 sufficient (I've seen them rated for video use at Class 4)? I know the classes denote the transfer speed:

Class 2 = 2MB/sec
Class 4 = 4MB/sec
Class 6 = 6MB/sec

I'm just not sure how that translates to real world performance if digital cameras need to write large files (over 8 megapixels). Of course, the reason I ask is because Fry's usually has the micro-SDHC cards for sale (with SD adapter for use in normal SD slot if need be), but they seem to only be rated Class 4, and I was thinking if I got the micro-SDHC card (Class 4), I could also use it in my blackberry for data-storage in pinch.
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post #2 of 6
4/2/09 at 4:41am

Re: SDHC cards - Class 4 or 6, does it matter?

Unless you are shooting many frames per second, the speed of the storage card shouldn't matter. Even then, it will take firing off a lot of shots before the card speed will matter. For example, I do not use very fast compact flash cards, and the only time I filled the buffer on my Canon 40D dSLR was when firing off about 20 shots at 6.5 frames per second when we were whale watching in Maine. So, unless you are doing action photography, save your money.

The only other area where the speed of the card comes into play is when transferring photos to your PC. Personally, I usually load the card into the reader, start the download and then walk away. So, if the download takes a couple of extra minutes due to card speed, I do not really care.
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post #3 of 6
4/2/09 at 10:47am

Re: SDHC cards - Class 4 or 6, does it matter?

I agree with Scott that with modern SLR's with a large buffer such as the one in a Canon 40D SLR you don't need a fast card. It's mainly needed to speed up transfers to and from your computer.

However another issue could crop up if you are going to use the card in a Point & Shoot camera set to video mode. When you're shooting 640 x 480 video at 30 fps if you don't have a fast card you could start dropping frames.

The pocket camera that I'm considering now to supplement my 40D is the Canon SD970 IS which may be released this month. I believe that it is capable of shooting HD video at 1280 x 720 @ 30 fps. Shooting video at that resolution requires a fast card.

Canon SD970 IS digital camera specifications: Digital Photography Review
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post #4 of 6
4/2/09 at 2:33pm
Thread Starter 

Re: SDHC cards - Class 4 or 6, does it matter?

So, I guess I would like to know if Class 4 is suitable for shooting video with the less expensive point-n-shoot digital cameras (as the 40D or 50D is out of my price range, I don't venture past $400 price tags when looking for digitial cameras these days - but if I win the lottery, then I might go a little higher). I did pick up a Canon SX10 IS, which does allow me to shoot video with it.
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post #5 of 6
4/2/09 at 4:17pm

Re: SDHC cards - Class 4 or 6, does it matter?

From what I've read, many of the small point & shoot cameras are barely able to keep up with a Class 2 Write speed of 2MB/Sec. As cameras get faster the need for Class 4 & Class 6 cards is to:

1. Enable the latest digital SLRs to keep up with the fastest buffer clearing speed for the max number of continuous frames.

2. Record HD video.

This:

Quote:
Some digital cameras require high-speed cards (write speed) to record video smoothly or capture multiple still photographs in rapid succession. Higher speeds of up to 200x are defined by specification 2.0.

is from here:

Secure Digital card - Wikipedia, the free encyclopedia

A class 6 card in a point & shoot camera only capable of recording 2 MB/sec is not necessary. But when you replace the camera with something faster you may wish that you had the class 6 speed cards.
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post #6 of 6
4/30/09 at 8:23am

Re: SDHC cards - Class 4 or 6, does it matter?

So a class 6 SDHC card is....shall I say..."recommended" for a Canon T1i doing 1080p video? These cards r very cheap nowadays that one can pick up an 8 GB Extreme III SDHC for $25!
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