# class 2 vs class 4 vs class 6 ?



## Etdashou (Mar 2, 2009)

Hi all,

I have a Canon Rebel XS.

I was wondering if I should get a class 2 or class 4 or class 6 memory card. Is class 6 really that useful for my cam? or is class 4 is enough? Is Class 6 really good only for video cam where memory access is higher?

I've been searching google on that, but I don't find anything about comparison for the class 2, 4 and 6...

thank you for any help on that.


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## Garbz (Mar 3, 2009)

Class 4 is more than enough. Basically the memory card is rarely the limiting factor. Cameras just can't process images fast enough. Even a basic cheap card will be often limited by camera processing speeds. It's when you actually copy the files to the computer (via a card reader, not the camera) that the memory card speed starts making a huge difference.


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## Etdashou (Mar 3, 2009)

Thank you for the response on that.


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## NateS (Mar 3, 2009)

I bought a Kingston Class 6 8gb for my D90.  Class 4 may be enough but when the class 6 is only 2-3 dollars more then why not go ahead and get it?  B&H has the Kingston Class 6 8gb SDHC cards for about 20 bucks.  (Although if I'd realized how few of shots the 8gb would hold on a D90 shooting raw I would have gotten 2 of them or a 16gb card.


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## Etdashou (Mar 3, 2009)

Yeah, sometime the price difference is 2-3 bucks, or sometimes it is 30-40$.

Like at Futureshop, I had a HP 8gb class 4 for 25$, and a Lexar Professionnal class 6 8gb for 70$.

I was wondering why should I choose one from the other...

But now that you guys say that the limitation is the camera itself and not the memory (most of the time), where can I see the max transfer rate of a camera? So I could choose a memory card that is similar to this speed or higher. Is it something we can see in a camera?

For the memory speed, Their is a nice website for this: Charts, benchmarks SDHC Memory Card Charts, Avergage Write Transfer Rates

Is there something similar for Camera?


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## NateS (Mar 3, 2009)

Etdashou said:


> Yeah, sometime the price difference is 2-3 bucks, or sometimes it is 30-40$.
> 
> Like at Futureshop, I had a HP 8gb class 4 for 25$, and a Lexar Professionnal class 6 8gb for 70$.
> 
> ...



Well, that's not a fair comparison because you are comparing two different brands.  Compare a 8gb SDHC card from Panasonic with a SanDisk and you'll see a $100 difference.  Compare 2 cards from the same company with a Class 4 vs 6 and the difference in price in pretty minimal.


I find it hard to believe that the card doesn't limit it at all.  I just got my D90 and shooting at 4fps (or is it 4.5??) I can hold the shutter down and only get 5 shots before it slows down from the 4-4.5fps.  Now I find it hard to believe that the D90 can only fire off 5 shots at full speed before having to stop or "slow down".  I'm guessing that if I had one of the really fast SanDisk cards that I'd get more than 5 shots doing this.


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## Etdashou (Mar 3, 2009)

yeah you'r right...

However, is the processing speed of cameras is something we can see before buying the camera? Or it is something not displayed.


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## NateS (Mar 3, 2009)

Etdashou said:


> yeah you'r right...
> 
> However, is the processing speed of cameras is something we can see before buying the camera? Or it is something not displayed.



I'm pretty sure that most reviews like DPReview show this data.  I'll go check.

Okay, I found it for the D90

http://www.dpreview.com/reviews/nikond90/page14.asp

It shows 11 shots in raw format at 4.5fps which is a lot more than the 5 I'm getting with my Class 6.....so apparently a class 6 is much slower than 133x or 30Mbps.  I'd like to know what the actual bit rate of a Class 6 card if anybody knows.  It was inexpensive and Kingston is a good brand so I'm not too worried about it, but if I start shooting sports then that 11 shot buffer would be helpful.

Okay I just read that the Class 6 card has a maximum read/write rate of 20Mbps which is 1/3 slower than the Extreme III Sandisk cards.  I guess that 1/3 is enough to allow an additional 6 frames at 4.5fps.


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## itznfb (Mar 6, 2009)

extreme III are class 6 / 20Mb/sec.
very few SD cards will reach more than 20Mb/sec. that's why higher end cameras use CF cards that go up to 35MB/sec or maybe higher.

i've found class 4 cards to be pretty limiting as they only get me about 1 or 2 shots after the camera buffer before significantly slowing the shot rate.


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