File recovery software SD card

[OldBoy]

Originally Posted by PatrickMcCluskey

Thanks all,
Thanks for the replies, I downloaded Zero Assumption and got all the files, but most of them I cannot open.
When I try to open them I am told, this file may be damaged THE FILE MAY BE TRUNCATED OR INCOMPLETE, ITS AS IF THERE HAS BEEN A GREY SHEET PUT OVER 90% OF THE IMAGE, FROM THE BOTTOM UP.
I wonder if most of this damage has happened when trying to open these files using stellar phoenix, as this programme allows you to view the files but wants you to pay around 70$ first ?

That suggests that the file is corrupt and Zero Assumption is unable to recovery what isn't there. This could have been caused by the card been defected, or the other program trying to access them or the cameras software didn't write the information correctly. The defected card is most likely to be the cause. Althought Chris P give a good description of file storage, he misses out the point that Jpeg files are compressed and they do that by recording each colour pixel position as a number which refers to the colour of the first pixel plus the location of each pixel that has that colour, whereas Tiff would record the colour and position of each pixel. So, if you lose the infomation in that first pixel that records the colour then it doesn't know what colour to give to the other locations that are based on that. It's a bit more complicated than that but gives a basic idea. This is why you get the grey sheet over the image and Truncated means that parts of the file are missing as the check-sum doesn't reflect the true size of the file, which is included at the end of the file data.

[chris-p]

OB is right (as usual). I kind of ran out of puff at the end of my last post so didn't go into JPEG compression. Ultimately if the indexing system is nadgered in so e way you've pretty much lost the whole file, even though all the content might be present.