General card speeds are 3mb/s read and write, sandisk has high-speed 9mb/s read and write, and sandisk also has professional ultra-high-speed cards that can read and write 20mb/s.

Currently, the SD cards in the market mainly use MLC type (multi level cell) and SLC type (single level cell).

In view of the small price difference between high-speed and low-speed cards with the same capacity, the author recommends that friends try to choose high-speed cards. It's not because the low-speed card is not enough, but because the high-speed card can provide longer continuous shooting to a certain extent when you turn on the camera's continuous shooting function.

In fact, the difference between the so-called high-speed cards and low-speed cards lies in the NAND flash memory they use. The so-called low-speed cards use MLC type (Multi level cell) NAND flash memory, which is mainly produced by Toshiba and Sandisk; while the high-speed cards use SLC type (Single level cell) NAND flash memory, which is mainly produced by Samsung. MLC has a higher storage density than SLC, so the price is more competitive. However, its reading and writing speed is slow, energy consumption is high, and its lifespan is short. Compared with SLC, the MLC architecture consumes 15% more current under the same conditions of use. Digital cameras and other digital mobile devices such as PDAs need power-saving, high-writing speed storage media. SLC NAND Products made of granules are the most ideal choice for consumers. Although the MLC architecture is relatively backward, it is highly flexible and can use older production to increase product density without additional investment in production equipment, which has a cost advantage. Therefore, most brands visible on the market still adopt the MLC structure, after all, this can reduce costs.

MLC type multi-layer unit technology, represented by Japanese manufacturer Toshiba, compared to SLC, MLC flash memory chips using multi-layer unit technology have higher storage density and more competitive prices, but read and write The speed is slower and the energy consumption is higher than that of the SLC type. It uses more 3.3v voltage and has a shorter service life. Generally, the number of stable accesses is about 10,000 times. Low cost and cheap.

Wei Technology's a-data SD card uses SLC type flash memory chips. SLC single-layer unit technology was launched by Korean manufacturer Samsung. Its energy consumption is lower than MLC. It uses more voltage of 1.8v, which can ensure stable access of about 100,000 times. However, the technical advantages and manufacturing costs are high. Apart from Samsung, only a few large manufacturers that have higher product quality requirements, such as ADATA, use SLC flash memory chips.

Several ways to identify high-speed SD cards:

(1). The one with gold letters on the back of the blue shell is manufactured by Panasonic. The quality of this card is exactly the same as the Panasonic SD card, and it goes without saying that the compatibility and speed are top-notch.

(2). The blue casing with engraving on the back is manufactured by d-elec. This card is also a high-speed card and has good compatibility, ranking second.

(3). The black case with gold characters on the back is made in Taiwan. It is also a high-speed card, but its compatibility is not very good. There have been incompatibility reports on some old dopods.

(4). The blue casing with white characters on the back is manufactured by Sandisk. It is a low-speed card with good compatibility, but some Panasonic models do not recognize it.