Photo Corners

A   S C R A P B O O K   O F   S O L U T I O N S   F O R   T H E   P H O T O G R A P H E R

Enhancing the enjoyment of taking pictures with news that matters, features that entertain and images that delight. Published frequently.

Around The Horn Share This on LinkedIn   Share This on Google   Tweet This   Forward This

25 July 2014

In this recurring column, we highlight a few items we've run across that don't merit a full story of their own but are interesting enough to bring to your attention (with more than 140 characters). This time we look at formatting or erasing your memory card, three sub-$2000 full-frame cameras a 50mm Leica for $8,250 and "unphotographic" images.

  • Derrick Story argues for formatting instead of erasing your memory card in a short video.
  • Kirk Tuck asks which full-frame camera under $2,000 you'd buy: the Sony A7, Nikon D610 or Canon 6D? Strictly hypothetical. In the real world, you might buy used.
  • With the cash you saved on that camera, amuse yourself with Lloyd Chambers as he takes apart the Leica 50mm f2 APO, which just went up from $7,350 to $8,250. He likes the larger but less expensive Zeiss Otus 55mm f1.4. Quality control has something to do with it.
  • In When is a photo not a photo?, Harold Davis admits to indulging in "post-photographic" techniques that amount to "digital painting, with photography as my source material." Just for laughs, he illustrates the piece with an in-camera studio shot using multiple exposures.

More to come...


I have to rebut the claim on the article about formatting is better that erasing leaves behind "cruft." This is incorrect. Deleting a file off of FAT32 (the vast, vast majority of cards will be formatted this) removes the file data entry from the FAT (file allocation table), which is the data about the filename, where it starts, etc. There is no "cruft" left behind. There is the file data blocks, yes, but formatting (unless you low level format) will leave those behind as well.

Now, when you do delete a file, it can leave holes behind in the FAT that will be reused, as well as where the file was located on the disk. When the next file goes to write, it might write to only some of the data spots available and might not write to all of them that are next to each other. This is called fragmentation and in a spinning disk, can impact performance when reading/writing a file because it needs to read/write at different spots all around the disk. On flash memory, this is not really an issue because the latency to read from any spot is essentially the same and so performance doesn't suffer. Doing a format simply re-creates the FAT table as an empty table and can be much quicker than deleting hundreds or thousands of photos (as the delete process does them one at a time).

Now, the exception to all this is flash memory itself. Most commonly some form of NAND flash memory. When going to write, the particular chunk (called a page) must be fully erased (reset to blank, essentially) before it can be written to. This obviously will slow down the write process. On CF cards, the protocol to read/write from them is some form of PIO/DMA/UDMA. Modern cameras and cards use UDMA, which is much faster than the older specs, with the latest being UDMA7. Cameras and cards that both can speak UDMA7 can do something called the TRIM command. What that does is let the camera tell the card when a file has been deleted, that a list of the pages that the file used can be pre-erased ahead of time, rather than when the write needs to occur.

Unfortunately, SD/SDHC/SDXC/UHS-1 doesn't support this, as those cards are quite simple. So you'll see an option for low-level format. This basically iterates through all of the pages and tells it to erase itself. This will restore performance on a used SD card, but can take quite some time. But only low-leve format, not a standard format.

Now, that's not to say it might not be useful to format a card now and again just to start with a clean & fresh FAT, but it's not strictly necessary every single time.

-- Aaron

Erasing is, as you point out, inefficient enough that we reformat. But we nearly fill our cards up before we bother (we don't start each shoot with a clean card, although we have plenty of room). Very efficient. No erasing, minimum reformatting.

We suppose that is manual wear leveling, too. But we wonder how various strategies affect a card's wear leveling.

-- Mike

Do you use SD cards? Those you'll want to do a low-level format to restore performance. For wear leveling, not sure how bad it might be on SD cards, but modern CF cards, especially with UDMA7, seem to look more and more like modern SSDs in a lot of ways, especially given they have TRIM support.

Personally, I wouldn't worry too much when it comes to wear leveling. Especially on the better quality brands. I've actually found I end up replacing cards simply to upgrade capacity long before they realistically would wear out. And especially these days, with the capacity of NAND, they have sufficient space to overprovision a bit which very much helps with wear-leveling. I imagine most/all CF cards support S.M.A.R.T. monitoring, just like HDD/SDD, so you could always check the status using a standard tool to read the data. Not in the camera, of course, but a USB card reader likely would work. Definitely if you put it into a CF->IDE/SATA adapter.

-- Aaron

BackBack to Photo Corners