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Thread: SDHC card speed ratings ???
2011-01-08, 16:25 #1
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- Dec 2009
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I found the info below on Wikipedia = bottom posted.
1) I thought that a 4MB card would come in classes 2,4,6,10. Same for others = a 10MB card would come in classes 2,4,6,10. Is that correct ????
I don't understand why the SIZE of the card ie the capacity matches the CLASS ie speed of the card in the Wikipedia info below.
Implies to me that only a 10MB card is a CLASS 10 CARD.............similar for other card capacities.
2) I have one BUDGET digital camera ( 5 megapixel ) that I have set for something like 2.5 megapixel since my shots are NOT Kodak moments and they are often BLURRY indoors in a bright room with no flash but clear outdoors.
I "imagine" that when the pix is taken that the camera can be moved while I am looking at the pix in the LCD as it is being written to the card.
I "imagine that the CLASS RATING of the card on the below chart affects the speed of writing to the card independent of the camera settings and speeds and will only affect the TIME BETWEEN SHOTS and have nothing to do with any BLURRING while the data is being written since the camera has been moved after the pix is taken. NEVER had a problem in past with my OLD BUDGET camera.
I had NO problems with blurring with my FIRST digital camera which was only 1.3 megapixel with a Smart Media card.
3) I know I have several questions above, but I am mainly interested in the FIRST item above.
As usual, thanks in advance for any advice.
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These are the ratings of some currently available cards:
Class 0 cards do not specify performance, which includes all legacy cards prior to class specifications.
Class 2, 2 MB/s, slowest for SDHC cards.
Class 4, 4 MB/s.
Class 6, 6 MB/s.
Class 10, 10 MB/s.
Even though the class ratings are defined by a governing body, like × speed ratings, class speed ratings are quoted by the manufacturers and not verified by any independent evaluation process. In applications that require sustained write throughput, such as video recording, the device may not perform satisfactorily if the SD card's class rating falls below a particular speed. For example, a camcorder that is designed to record to class 6 media may suffer dropouts or corrupted video on slower media. On slower class cards, digital cameras may experience a lag of several seconds between photo-taking, whilst the camera writes the picture to the card.
Since the class rating is readable by devices, they can issue a warning to the user if the inserted card's reported rating falls below the application's minimum requirement.
2011-01-09, 04:38 #2
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Secure Data High Capacity merely refers to the size, above 2GB I think. Speed is at the whim of the manufacturer, more expensive usually equals faster.
I always run my camera at the highest resolution, just in case that photo turns out to be the one I want to keep. Hard disks are cheap these days so saving the extra data is easy.
Blurred images are inevitably caused by moving the camera whilst taking the picture, which may also be the time it takes to write to the SD card - this depends on the camera. The speed at which the image is written to memory is entirely up to the manufacturer, again, more money usually equals faster write speed and more frames per second. I suggest you test taking pictures in low light by using a table to steady the camera and then holding the camera free hand. (I always attempt to take several pictures in quick succession to try to get the best picture.)