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Question about card management with 30,000+ images

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Offline andyroo

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Question about card management with 30,000+ images
« on: 14 / December / 2012, 20:20:48 »
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I am using CHDK on a D10 to take repeat aerial imagery and generate orthophotos and digital surface models. So far I've done 20 flights, and I average about 1,500 - 2,000 photos/flight (6 - 8 GB in superfine). On my 19th flight, my intervalometer froze after about 800 images, but the camera was still on after the flight. I think that the card had a write error, but that got me thinking about flash memory "lifetime" and best card management.

I had been downloading images, deleting the DCIM directory (while still in the computer) and putting the card back in the camera for the next flight. Also I would often start reviewing the images on the card as they were copying to the PC.

After reading up on flash memory I decided that viewing the images at all on the card was probably not wise, and I am wondering if after each flight I should use the in-camera "ERASE ALL" option instead, or if it would be better to format the card in-camera every time, then copy CHDK back over (or some hybrid, like reformat every 5th flight or something).

Also wondering how frequently I should plan to swap out the cards or if there are any utilities to evaluate the card's life/health based on the amount of wear on the cells. to me it seems like the card should be good for many more images than this. But to be safe I changed cards.

I am using 16GB SDHC class 4, with swapped partitions, taking pics every 3 seconds. CHDK loads at boot and auto-starts my timelapse so all the pilot has to do is turn it on and mount it, then turn it off at the end of the flight.
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A720 1.00c | D10 1.00b |SX220 1.01a | SX230 ? | SX30 1.00p CHDK ver. 1.1.0-r1727
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Offline waterwingz

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Re: Question about card management with 30,000+ images
« Reply #1 on: 14 / December / 2012, 20:45:25 »
Quote from: andyroo on 14 / December / 2012, 20:20:48
After reading up on flash memory I decided that viewing the images at all on the card was probably not wise,
The"wear" on an SD card is a function of how often an individual cell memory page is erased so that it can be written to.  If you write the same data to a page, no erase occurs    And reading the card should have no effect on card life.

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and I am wondering if after each flight I should use the in-camera "ERASE ALL" option instead, or if it would be better to format the card in-camera every time, then copy CHDK back over (or some hybrid, like reformat every 5th flight or something).
Again,  once CHDK is copied to a card, those cells never change again, so CHDK should stay on that card forever.

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Also wondering how frequently I should plan to swap out the cards or if there are any utilities to evaluate the card's life/health based on the amount of wear on the cells. to me it seems like the card should be good for many more images than this. But to be safe I changed cards.
I am using 16GB SDHC class 4, with swapped partitions, taking pics every 3 seconds. CHDK loads at boot and auto-starts my timelapse so all the pilot has to do is turn it on and mount it, then turn it off at the end of the flight.
While SD card cells have a write limit between 10,000 - 100.000 (I forget the current value),  the card controller also moves the write locations around automatically to assure no single location gets pounded with continuous writes.  So your card will actually last a lot longer than just a few 100K writes.


« Last Edit: 14 / December / 2012, 22:30:07 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline lapser

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Re: Question about card management with 30,000+ images
« Reply #2 on: 14 / December / 2012, 22:32:28 »
There are a lot of reasons a script may freeze. A good rule in evaluating a freeze is "It's always software, never hardware." I've found SCHC cards are very reliable.

One problem may be using partitions. I format the entire card, even my 64GB card, with FAT32 using a Windows program called FAT32Format.exe. It works great. There's really no need for partitions any more.

It's best to start each flight after deleting all the pictures. You can transfer all the pictures and log files off the card and delete them using a card reader. The camera erase all option in play mode also works for pictures in the DCIM folder. I use this to delete any test photos off the card before starting a time lapse.

My high speed time lapse tests consist of over 2,000 pictures (usually of the wall). The freezes I've had have all been software related, not hardware.

According to philmoz, it's best to take the first picture with the camera right after booting, and before starting a script. That insures the camera grabs its memory first, rather CHDK and prevents fragmentation of memory.

I've heard reports that the shoot() function sometimes hangs after a random number of shots, stuck with get_shooting() true. My impression was it could be from returning too soon after releasing the shutter button, but this is just a guess. But if you're using shoot(), this might be causing the problem. Search the forums for shoot() bug, and you may find something useful.

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Offline waterwingz

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Re: Question about card management with 30,000+ images
« Reply #3 on: 14 / December / 2012, 22:43:29 »
Quote from: lapser on 14 / December / 2012, 22:32:28
There's really no need for partitions any more.
There is for cameras released prior to 2011 - like the D10. They will not boot from a FAT32 partition and FAT16 partitions max out at 4G.

Ooops.

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Ported :   A1200    SD940   G10    Powershot N    G16
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