Question - Memory Cards

[FL Naturelover]

I currently use class 10 SD cards for my Canon Rebel T1i. My husband just found memory cards by Delkin Devices. 8GB for $15.99 24mb/s 163x. What do the other numbers mean and how is this different from my current PNY professional 8GB class 10 card 20MB/s? Do I really need it? It seems that Delkin is the only one with these very high MB/s.

[pierces]

I currently use class 10 SD cards for my Canon Rebel T1i. My husband just found memory cards by Delkin Devices. 8GB for $15.99 24mb/s 163x. What do the other numbers mean and how is this different from my current PNY professional 8GB class 10 card 20MB/s? Do I really need it? It seems that Delkin is the only one with these very high MB/s.

 

Paraphrased from an article I did on camera choices:

 

Bombarded with still more Xs…40X, 80X, 133X, even 600X! An “X” in this case refers to multiples of the playback speed standardized for the CD-ROM which is 150 kilobits per second. Note the “bits”. Files are measured in 8-bit bytes so a 166X (equivalent to about 25mbits/s or a little over 3MB/s ...Class 4-ish) card can, theoretically, transfer a 3mb file in a second. In practical use the rating is usually for the minimum sustained write speed and will actually transfer a bit faster. Again, mileage varies. Also keep in mind that a camera may not be able to write at such high speeds due to limitations of the processor and more techie factors. If the difference in price is fairly small, get the fast one. Remember, though, the 166X card may not always provide better performance than the 40X card in your camera. Note: The Xs aren't completely useless if your camera can't use them. If you have a fast card reader, you can really see the difference in the faster card while downloading images to your computer!

 

Your T1i writes pretty quickly and will not entirely waste the speed of a Class 10 card, especially with video. Spending more money on the faster UHS1 cards, as mentioned above, would speed downloads with a compatible reader, but wouldn't make you camera's frame rate increase beyond it's current 3.4 fps.

 

BTW, the ease of understanding the "Class" system with 6 equaling 6 MB/s and so on is the main reason manufacturers have moved from the old "X" rating to Class or simply stating the minimum sustained read/write speed on the card.

 

Dave

[awboater]

There are actually two specifications to a memory card; Class and Speed.

 

Class is the Minimum long term speed of the card.

 

Speed is the Maximum short term speed of the card.

 

If a card is classified as a Class 10 - 30Mb/s then;

 

- It's a Class 10 card, with a Minimum of 10Mb/s throughput.

- It's Speed is a Maximum of 30Mb/s.

 

Therefore, Class determines how well video will record as video is a long-term data stream. It will also determine how fast you can upload the card as that is also just a data stream.

 

The speed rating is for short durations and cannot be sustained for long periods of time. This rating is useful for knowing how well a camera can write to the card in continuous or burst shutter mode.

 

If you are not doing video, then Class is not really all that important. And if you are not doing continuous shutter photography, then Speed is not very important either. In those situations, a Class 2 card can sometimes suffice.

 

Oddly enough, a faster card may improve the performance of a compact camera more than a DSLR. DSLRs have on-board internal buffers to assist in temporarily storing a photo so that there is minimum shutter delay. For that reason, the speed of the card matters little as long as the buffer does not completely fill up.

 

Unless you are shooting continuous, the camera's buffer will not likely fill completely, so while you are writing to the camera's buffer at a high speed by taking photos, the buffer is being off-loaded at a slower speed to the memory card.

 

But most compacts do not have an internal buffer, so the electronics write directly to the memory card, which along with slower electronics inherent to compacts, is a reason for the shutter delay in these cameras.

 

So a faster card may improve the shutter delay of a compact camera. However, the electronics are often marginal in these cameras anyway, so any improvement by using a faster card may or may not be realized.