USB 2.0, USB 3.0 And OTG: Choosing A Card Reader

Interface speed is only a bottleneck sometimes

USB 2.0 is slower than any modern memory card. For a handful of photographs that does not matter, and the price difference is real. For a card full of video it is the difference between a transfer that fits into a working session and one that does not. The honest rule: if the customer shoots video, specify USB 3.0; if the reader is a line item in a bundle, 2.0 is usually the right economics.

Real speed depends on the card too

A USB 3.0 reader does not make a slow card fast. Transfer rate is set by the slowest link in the chain: the card, the reader and the host port. This is why we do not publish a headline megabytes-per-second figure that no real card would reach, and why a measured figure for a specific card is more useful than a marketing number.

The connector decides where it can be used

A USB-A reader works on most laptops and no phones. A Type-C reader works on modern phones and laptops and not on older machines. A dual-connector reader, with USB-A at one end and Type-C at the other, works on both without an adapter, which is what makes card-to-phone transfer practical on location. On a phone, the device also has to support USB OTG, which most modern handsets do.

What OTG actually is

USB On-The-Go lets a device that is normally a peripheral, like a phone, act as a host and accept peripherals of its own. It is what allows a phone to read a card reader or a flash drive. It is a device capability, not a reader capability: the adapter or reader simply presents the right connector, and the phone does the work. High-draw peripherals may need their own power, because a phone supplies limited current.

Housing is a durability decision

A reader that lives in a camera bag gets crushed, dropped and filled with grit. Aluminium alloy housings survive that; moulded plastic cracks where the connector meets the body. For a bundle component or a giveaway, plastic is the right economics. For anything a professional carries, it is not.