Card Readers and a Sensible Photo Workflow

Transferring photographs is one of those jobs where the bottleneck moves depending on what you own, and the card reader is the component most often overlooked. A fast card and a fast computer connected through a slow reader transfer at the reader’s speed.

UHS-I and UHS-II

SD cards use a bus standard, and the two common ones are UHS-I and UHS-II. UHS-I tops out around 104 MB/s. UHS-II adds a second row of contacts on the back of the card and reaches considerably higher.

The critical point: a UHS-II card in a UHS-I reader works perfectly and runs at UHS-I speed, because the reader has no contacts for the second row. Every part of the chain has to support UHS-II for the speed to appear.

Most readers built into hubs and laptops are UHS-I. If you have paid for fast cards and transfers are slow, the reader is the first thing to check.

Card speed markings

Cards carry several ratings and they measure different things. The C in a circle is the old speed class; U in a bucket is UHS speed class; V followed by a number is the video speed class, and it guarantees a minimum sustained write speed.

For photography, the headline read speed matters for transfers and the minimum write speed matters for burst shooting. For video, the V rating is the one to follow, because sustained write is what stops a recording failing.

Reader connection

A reader on a USB 2.0 connection is limited to about 40 MB/s in practice regardless of the card. USB 3.0 and above removes that ceiling.

Look at what the reader plugs into as well. A USB 3 reader in a USB 2 port runs at USB 2 speed, and the ports are not always labelled clearly — the blue plastic tongue is a good sign but not a guarantee.

Simultaneous slots

Many multi-slot readers share a single controller, so only one slot works at a time and using two halves the speed. Where a manufacturer states independent or simultaneous operation, that is a meaningful feature; where they do not, assume shared.

Phone and tablet adapters

Camera adapters that connect a card to a phone or tablet are genuinely useful for reviewing and sharing in the field. They are usually slower than a computer reader, and some are limited by how much power the device will supply.

Most modern phones and tablets handle standard cards without additional software. Where a product claims no app required, that is normally accurate for the main file types and less reliable for camera raw formats.

A safe copying routine

1. Copy, do not move. Moving deletes as it goes, so an interrupted transfer loses files.
2. Copy to one location, then verify the file count and total size.
3. Copy to a second location before deleting anything.
4. Only then format the card — in the camera, not on the computer.
5. Do not remove a card while an activity light is on.

Formatting in the camera rather than the computer matters: the camera writes the directory structure it expects, and a card formatted by a computer sometimes produces odd behaviour on the next shoot.

Card care

Keep cards in a case, not loose in a pocket or a bag. The contacts are exposed and the plastic bodies crack under pressure.

Rotate cards rather than filling one repeatedly, and retire any card that has produced a read error. Flash memory fails without much warning, and a card that has failed once is not trustworthy for a job that matters.

When the reader is not the problem

If transfers are slow with a fast card in a fast reader on a fast port, the destination drive may be the limit. A slow external hard drive over a shared hub connection can be considerably slower than the card.

Test by copying to the internal drive first. If that is fast, the destination is the bottleneck rather than the reader.

Supported card formats, bus standards and whether slots operate simultaneously are listed on each product in adapters and card readers.

Naming and folder structure

Decide a folder convention once and use it every time — a date-first folder name sorts chronologically in every operating system without any software. Renaming files by date and sequence at import removes the problem of duplicate camera filenames when two cards are combined.

Cameras restart their numbering, so files with identical names from different shoots are common. Discovering that during a copy is how photographs get overwritten.

Backups that actually exist

Two copies on the same computer is one copy. The usual guidance is three copies, on two different types of media, with one kept elsewhere — and the version of that most people manage is the internal drive, an external drive, and a cloud sync.

Whatever the arrangement, test it once by restoring a file. A backup that has never been restored from is a plan rather than a backup, and the moment to discover the difference is not after a card failure.