Today’s Question: After I’ve transferred a shoot to my hard drive, does it matter whether I re-format the media card in the camera or simply erase all old picture files, in terms of capture speed, write speed, quality or anything else for my subsequent captures?
Tim’s Quick Answer: I recommend formatting the card in the camera rather than erasing images from the card using your computer, primarily because formatting will recreate the “table of contents” for the file system on the card. This approach can help avoid issues with corruption occurring over time with the file system on the card.
More Detail: In theory it really shouldn’t matter whether you erase all of the images from a card on your computer or format the card in your camera. As long as the space consumed by those photos has been freed up so you can capture new images, you should be in good shape.
Unfortunately, the file system information on the media card can become corrupted over time, and so it is a good idea to use the format option on your camera to “erase” the card and prepare it to be used for new photos. In essence, this process involves re-creating the file allocation table on the card, which is the “table of contents” used by the card.
Most cameras, by the way, don’t actually remove your image data from the card when you format the card in the camera. The same is true in most cases when you otherwise erase images from the card. The actual image data remains on the card, but the “table of contents” is updated to indicate the photos are no longer there and that the space that had been consumed by the photos is available for saving new images. This is what makes it possible to recover lost images that have been accidentally deleted, even if the card was formatted. As long as you haven’t captured new images (or you use a method of erasing that actually over-writes the image data) you can use special software to recover images you thought were lost.