why / when reformat SD card?

Discussion in 'Digital Darkroom' started by jtk, May 27, 2008.

  1. jtk


    One of the usual suspects recently advised occasionally reformatting SD cards in

    Is there any reason for that?

    What would change the format?

    If I used my SDs in a digital audio recorder and then in camera, would that
    likely call for reformatting? Hasn't yet....
  2. There are a lot of things that can go wrong when the card has been touched (especially, written-to) by an external device. Even just popping the card into a card reader on your PC, and having its native thumbnailing routine plow through it trying to help you view that device's contents... that changes the data on the SD card. It's up to the device doing the writing (your computer, a storage device, or the audio recording widget) to honor the file system on the card, and stay within the bounds of the formatting found thereon... but they don't, always, or might be interrupted by some other unforeseen event.

    More to the point, it's not unheard of to pluck the card out of the other device (a card reader, for example) while the thing that's talking to it isn't quite done closing up the files it has just altered. The very nature of the file system on the card (or a hard drive, for that matter) is that writing a file to it means pushing that data over AND then updating the file system information that describes the name, date, etc., and other housekeeping data that makes the file appear as in item in the file system. If any of that becomes half-baked, the file system is then corrupt. Reformatting it clears the deck, and creates a nice, fresh file system and housekeeping space on the storage device/card/drive.

    Because the last thing you want to go wrong is the process of the camera writing data to the drive and correctly establishing the file name, etc., it's ideal to let the camera set up shop on the card in the way that it sees fit. Formatting the card also gets rid of any other unpleasantness that might have found its way onto the card... viruses, hidden files, etc.

    MUST one, on any particular schedule? No. But when I care about what I'm shooting, and the card has been updated in any way by another device, I take mere seconds to format the card in-camera. Every time (well, every time that I care about the images or the event I'm shooting).
  3. I don't use many SD cards at the moment but do use compact flash cards. I try to remember to reformat my cards about every third use or so. I only use the camera to erase photos on card never the computer. I also go through all cards and reformat them before an important shoot (wedding). If I was using the same card in two devices I would format it in the device I was using it in before use. Just my 2 cents worth John
  4. Hello John.
    I happen to agree with the idea of formatting and re-formatting your camera picture cards in the camera.

    Your camera owners manual will tell you that new picture cards should be formatted after they are inserted but before they are used.

    The basic purpose of doing a FORMAT on a picture card (new or otherwise) is so that all the available "raw" digital address space on the card can be: a) surveyed by the firmware, to find out how much digital space is there, b) organized into sectors or blocks that can be assigned unique numbers, c) the vast group of sectors is than organized into tables of available space, usable by the camera when it saves a picture. This structure could be called a "file system".And this logical structure is what supports the entire "handling" of the camera picture files when they get saved to the card.

    A secondary, but still very useful, function of doing the camera FORMAT on the pciture card (new or used) is that it WIPES CLEAN the picture card, erasing all the previous user data, and effectively "reclaiming" that space so that new pictures can be saved there. A suitable metaphor would be like when the Teacher has a chalkboard full of data, and wants to write something new. He has to ERASE all the old info, to reclaim a nice clean space, and then he can resume teaching.

    A third function that the camera FORMAT does is to provide you, the primary operator of the camera, with a clear, digital, and positive CONFIRMATION that the FORMAT succeeded. This serves to verify that the picture card (new or used) is functioning correctly inside the camera, using the camera's own low-level memory card I/O drivers and algorithms. This confirmation is a NICE confidence factor to have, especially if you are about to plunge in and take hundreds of pictures. The inverse is also true. If you are unable to format or reformat a particular picture card inside your camera, and you are pretty sure the camera and batteries are OK, then thats pretty good proof you need to try another picture card before embarking on the critical shoot.

    ANother way of vieweing it is that the picture card is a CRUCIAL, CRITICAL, and ESSENTIAL component in the camera for successful picture taking, especially if you are a commercial photographer, and being paid to deliver contract deliverables.

    Now in a perfect world, nothing would ever happen to the picture card, and you would only need to do a FORMAT on it once, at the factory. But we live in a far from imperfect world. There are MANY different kinds of digital cameras that might be using this card, so the mfgr cannot garuntee the card will work right in every camera straight from the factory. That is why the camera manuals advise you to format and reformat new and used picture cards in your particular camera.

    Sometimes the individual data sectors or blocks on the memory card get corrupted. That is, the digital contents of those blocks get changed from what is supposed to be there, into something partially or completely different. For example, this can happen if the card gets too near to influences with very strong magnetic fields, like strong magnets, or large electric motors or generators, or old-style telephones, or florescent light ballasts, or large transformers. In cases like this, the picture card, being an unshielded memory chip, can be partially erased to greater or lessor degree. If the data corruption occurs in sectors that were assigned to a previously taken picture file, then that image is corrupted. And when you look at it on the computer, either the file will not be readable, or it will be obviously damaged by some kind of corruption. If the corruption occurs in the file's header, then you probably wont even be able to load it into an application.

    If the corrupted blocks were part of those being used to define the picture card's "file system" (ie, naming the folders, listing all the files, and mapping the free space), then you may actually lose the ability to access the files referenced and tagged by that part of the file system. You would the have to do some kind of repair to the file system to clean it up, and restore at least "read" access to the card's file system.

    In addition to data block corruption, a picture card can also experience a "hardware failure", an event in which some of the intricate integrated circuits are actually damaged beyond repair. Generally speaking, picture cards and similar devices, like CD micro-Drives, are sensitive to stray static-electricty shocks. The technical name for this is ESD (Electrostatic Discharge). This is when latent static electrical energy that has built up in your hands, hair, clothes, body, furniture, and surroundings causes a very tiny but very high voltage static-arc to reach across and zap the gold contacts on a carelessly handled picture card. In this case, the high voltage of an ESD is enough to blow out some of the picture cards internal micro-circuits. And that causes hardware failure on those sets of circuits. Whatever addresses are being powered and driven by those circuits would cease to function. And the next time you did a FORMAT, you would probably see an Error Msg about a problem with the card.

    And, being tiny but sophisticated electronic circuits made up of large numbers of individual components, a card can experience hardware failure due to simpley old age and normal component failure. No electronic device or circuit is warrantied to last forever. Components do and will fail after repeated cycles of use, formatting, storage, handling, and reuse.

    You can use the same SD cards in both your camera and your voice recorder IF both devices were designed and "specced" to accept and operate with that one type of picture card media, ie SD type media. The manuals or marketing materials would tell you that. But on either side, the card still has to recieve a low-level FORMAT in order to wipe the surface clean and prepare the File System. If you format the card in the camera, and that goes OK, then you know the card component is functioning correctly in the camera and ready for pictures. But that is not a confirmation that the card will run OK in any other device, like the audo recorder. The fact that in your case the card is functioning OK in both devices simplt means that both devices are compatible with an SD picture card, and that the File System that was put on the card, the last time it was formatted, is compatible in both devices. But you might experience a card failure if you were to try that card in some other kind of device.

    If you have copied off ALL the picture files, audio fils, whatever, from the card and uploaded them to your PC, and followed that up with one or two DVD backup disks of the files - then you have nothing to lose by doing the camera FORMAT on the picture card in the camera. And what you GAIN is a) rdy access to ALL the available space on the card, b) positive confirmation that card is functioning correctly, and C) sure knowledege that the card has a brand new file system in place, virgin, and clean, and ready for lots of good picture taking.

    It only takes a few seconds to format the picture card. It does not hurt the camera, nor the picture card (if, in fact, the picture card is OK to begin with). And the successful FORMAT tells you the card is ready to go, and that gives you a good confidence factor.

    My own habit is to do 3 sequential FORMATS on any memory card I put in my digital cameras. That gives me a high degree of confidence that the cad component is AOK and will handle correctly everything I take a pciture of. And when I'm done, that night, I upload EVERYTHING on the card to the laptopm, and then burn a couple of backup DVD disks. If I'm using a multiple # of cards for one camera, I will follow a rotation, so that all the cards get about the same amt of wear & tear.

    My recemmendation for your setup is that you pick some of your cards to dedicate them for the Audio Voice Recorder. And dedicate the others for use in the digital camera. For either device, when you put a card in, do the FORMAT function thats built into the device.Dont do a FORMAT on the computer side. Use the computer & card reader only to upload and copy the files from the card reader to the computer. And dont move the cards from one device to the other. That will simplify things, and will keep each set of cards set apart for either the camera or the voice recorder. Finally, get into the habit of regularly transferring all the files OFF the SD card and onto the computer, and then, without delay, make one or two backup disks of all the new files. That way, if something does go wrong in the card, or in the camera, or in transit, or anywhere in the process, you will have backup disks ON HAND to recover those pictures.

    Two non-technical reasons why I hold these views are simply: a) experience, and 2) Murphey's Law. As you likely know, Murphey;s Law says "anything that can go wrong will." I think Mr. Murphy must have been a Photographer.! The suggestions outlined here will help you operate with confidence in a process flow where any number of things might go wrong without any warning. If you are an amatuer photographer and not trying to deliver contract deliverables, then perhaps you can live with a sudden picture card failure or corrupted file system resulting in lost or mortally wounded picture files. But if you are shooting something like a wedding, and theres a lot of pressure, and people are paying you a thousand dollars or more to get all these pcitures, THEN you must reckon that Mr. Murphy just MIGHT show up and bad things might happen, even to your picture cards and the data stored on them.
  5. jtk


    Wow! Looks like I asked the right question in the right place!

    Gentlemen, thanks. Will do.

  6. There's lot's of good information here, but one thing I noticed that stood out was that when you reformat anything it does not erase it. It only deletes the main header, basically the title. All of the original data is still there and can conceivably be restored or undeleted. The FBI does this sort of thing all the time when they confiscate computers from suspected criminals. Digital data recovery is a big business. So, don't rely on the delete button or reformatting to 'clean' your files. There are ways to do that, involving rewriting various patterns over the 'surface' until it becomes totally unreadable. But, that said, reformatting is a good way to re-establish all the needed parameters of your device, ensuring that you will get that perfect shot. My biggest question is: how can I reformat my SD cards (done in my Kodak EasyShare camera) so I can use it for something else, like recording music or files from my PC. My PC just says 'unrecognized device'.

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