Canon 5d Mark III Dual Card Slots
Photo Gear,  Travel

Travel Light for Photography – Canon 5D Mark III Dual Card Slots

Normally when I travel for photography, I bring along my laptop and a small external hard drive to back up my photos.  I also don’t reuse my CF cards so that I have redundant copies of my photos until I upload them when I return home.

There are times where I don’t want to carry all that gear along.  Here are some examples of trips where I don’t want to carry a lot of gear but still want to have back ups of my photographs during the trip.

  • Short trips
  • Small commuter flights
  • Day trips
  • Overnight backpacking hikes

Writing your photos redundantly to both card slots on your DSLR can save your from bringing your laptop and external hard drive on these short trips.

On a recent business trip to Washington D.C., I tested this out with my Canon 5D Mark III.  It was only a 3 day trip and I only had about 20 hours to photograph prior to the start of my business meetings.  I had limited time between the end of the meeting and my flight at Reagan National airport so I only brought a non-photography backpack and a small luggage that I checked at the gate.

I brought 3-16 GB CF cards and 3-16 GB SD cards for back up.  I had time for an evening photo shoot after arrival and another shoot the following morning.  The 6 cards turned about to be plenty and I had back up protection of my photos throughout the trip.

Since I shot only in single shot mode during the trip, I did not notice any degradation in shutter speed performance or in delays in the buffer writing to the card.  If you are shooting action scenes like birds in flight, this may not work for you.

CF and SD Cards

Performance Test for Writing to Dual Card Slots

When I tested this with my Canon 5D Mark III using continuous high mode, the buffer filled much quicker when writing RAW files to both cards vs. only writing to the CF card.  Here is the number of shutter clicks before the shutter slowed down waiting for the buffer to clear when writing RAW files to the card(s).

  • 20 shutter clicks when writing to only the CF card
  • 13 shutter clicks when writing to both the CF and SD cards

It also took considerably longer for the buffer to empty when writing to both cards.  For this test, I used a 600X CF card and a category 10 SD card.  The SD card slot on the 5D Mark III appears to be considerably slower than the CF Card slot.

Steps To set up the Canon 5D Mark III to Write to Both the CF and SD Card Slots

  1. Press the Menu button
  2. Select the first folder on the yellow tab with the wrench icon
  3. Select func+card/folder sel.
  4. Select the Record func. and select either Record Separately or Record Multiple

Record Multiple – will record the same file type and size to both slots

Record Separately – will allow you to write different file types/sizes to each card slot.

Standard – will write to only one card.

Next time you go on a short trip, try using the 2nd card slot on your DSLR to backup for your photos during the trip.

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