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Old Dec 8, 2005, 10:19 AM   #1
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I'm looking at some SD cards for my DSLR and have a question.

While I want a good deal, I want to get a card that will keep up with my needs. I see write speeds and figure the bigger the number, the faster the write speed.

my question is as follows:

I see one card that has a write speed of 133x for $100, and I then see a card that has a 7mb/sec for $140. I figure that the 7 mb/sec is the better card. What is the 133x then?
I hope my question is clear...I just need to know what the standard of measure is for the 133x, 30x etc....since they say 7 mb/sec for the other.

Thanks!
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Old Dec 8, 2005, 10:56 AM   #2
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Rbothell wrote:
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I see one card that has a write speed of 133x for $100, and I then see a card that has a 7mb/sec for $140. I figure that the 7 mb/sec is the better card. What is the 133x then?
Most manufacturers consider 1x = 150kb/second.

So, a 133x speed would imply a transfer rate of approximately 20mb/second.

But, you really can't go by the rated card speed to tell how well a card is going to work in a given camera model. It's far more complicated than that. You've got processing bottlenecks in the camera, differences in the way cameras communicate with different brands of cards, etc.

For example, I've seen cases where old 4x cards ran circles around newer 66x speed cards in some models. Your best bet is to ask other users of your camera how well one card works versus another.

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Old Dec 8, 2005, 12:20 PM   #3
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...also, if the camera has a built in buffer memory (which the data/pixels go thru before being shuttled into the card), that will tend to negate or hide any effects of card speed (until/unless the buffer fills up with rapid shooting or after a bit of operation in burst or movie mode).
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Old Dec 9, 2005, 1:38 PM   #4
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To avoid confusionyou should case your Bs, i.e. 1x = 150KB/s (KiloBytes, not Kilobits), upper case B means bytes,lower case b means bits. 150KB/s = 1.2Mb/s.
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Old Dec 9, 2005, 3:08 PM   #5
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Caelum wrote:
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To avoid confusionyou should case your Bs, i.e. 1x = 150KB/s (KiloBytes, not Kilobits), upper case B means bytes,lower case b means bits. 150KB/s = 1.2Mb/s.
I don't know what they're teaching in schools anymore, but you're not the first person I've heard say that in recent times.

However, I can assure you that nobody used to try and show the difference between bits and bytes via the case of the letters when I was learning about it years ago (and I spent a number of years in the telecomunications industry, working with digital)..

It was more common to use lower case kb for kilobytes and mb for megabytes, and spell out bits if not referring to bytes (kbits/sec, mbits/second; or somtimes Kbits/second or Mbits/second -- often shortng the seconds to just s or sec). Kb, kb, or KB always referrred to kilobytes. You spelled out bits if not referring to bytes.

If not referring to transfer rates (only memory), it was common to shorten it to just k. For example, a PC with 64k of ram (representing 64 kilobytes or 64kb; not KB as you see often in recent times).

But, you're not the only person I've seen say that it's more common to show the difference via case now.

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Old Dec 9, 2005, 4:15 PM   #6
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I don't know what it was like in the telecommunications industry, I guess I'm approaching it from an IT perspective (read: geek). I studied computer science twenty years ago and that was the way I learned it then. As a programmer analyst this is the only nomenclature I have come across. Every IT company, including Microsoft, use it, just check all of their software, like Windows Explorer file sizes(MB) or how your network speedis reported (Mbps), for example. Check when youdownload something, it will use B forbytes and b for bits for the transfer rate.SameonLinux and Apple. I think with the prevalence ofcommunication speeds indicated in bits, and sometimes bytes, and abbreviated, this is a necessity to avoid confusion.
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Old Dec 10, 2005, 5:48 AM   #7
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I think you've just been dragged, screaming and kicking, into the modern technological era Jim :G.
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Old Dec 10, 2005, 7:53 AM   #8
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Stevekin, I think so, too.

Caelum, now that you mention these terms, Kbps and Mbps were the way you often saw speeds mentioned in telecom, too. When I saw that, it jogged my memory.

I've been in Military Communications, and then in the Communiations Equipment Industry for about 6 years, then in the Long Distance industry for a number of years, and even did a stint as Director of Network Control Center Products for an International Wireless Company.

IT, sure.... I was part of Network Systems Planning and Development with the Long Distance company, and even designed and implemented their first Private Line Digital Cross Connect Management System (managing DS1 Switches with DS0 Matrixes), and followed with the integration of Digital Voice Swtiches into the same Management System.

Trust me, that was IT. We had to worry about the servers, networks, workstations, associated applications, etc. After leaving Telecom, I managed MIS Network Services for a Transportation related company (including the Network Engineering and IT Help Desk groups, supporting over 140 branches and thousands of employees.

Stevekin, I even visited your neck of the woods (UK) while with the wireless company (visiting a company based in the UK that we had acquired at the time). I remember it well. I stayed in the Pontlands Park Country Hotel in Chelmsford. But, everyone was too darn formal there for me. When I asked about a bar (even though they had a rather formal lounge), you'd get a smug response like "we're not that type of establishment sir").

Whem I asked about what time dinner was served, I'd get a response like "what time will you be requring dinner, sir". That place was *way* too formal for my tastes. LOL The company there booked the accomodations for me, and I told 'em that if I came back again, to book me in a large chain hotel of some type. I think that they were shocked that I didn't prefer a place like they'd booked me in.

But, we never referred to speeds in megabytes per second, either (not when I was in telecom). Even the fastest optical systems (at least then), where we may have 45 DS3's riding on one, were rated in bits per second (even when you reached speeds of gigabits per second). So, there was never any confusion over what you were referring to (bits versus bytes). Times change I guess. LOL

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