Good question, and I don't know the answer, but (Wikipedia):
"The derivation of Exif from the TIFF file structure using offset
pointers in the files means that data can be spread anywhere within a
file, which means that software is likely to corrupt any pointers or
corresponding data that it doesn't decode/encode. For this reason most
image editors damage or remove the Exif metadata to some extent upon
saving.[7]"
"Exif data are embedded within the image file itself. While many
recent image manipulation programs recognize and preserve Exif data
when writing to a modified image, this is not the case for most older
programs. Many image gallery programs also recognise Exif data and
optionally display it alongside the images."
http://en.wikipedia.org/wiki/Exchangeable_image_file_format
A quick test shows that even PS 7.0 modifies this data, but not to any
great extent.
Photos that are cropped lose the vast majority of the data.
My only suggestion would be to use newer software for your editing.

On Sat, Jul 7, 2012 at 8:11 PM, Peter Shkabara <[log in to unmask]> wrote:
> I just discovered that some programs I had used wiped out the EXIF
> information in many of my JPG files. This info shows what camera took the
> photo, and most important, when the photo was taken. In addition to the EXIF
> info being blank, there are comments in the file. There are apparently two
> programs involved base on the comments:
>
>
>
> 1 - Created by AccuSoft Corp.
>
> 2 - LEAD Technologies Inc. V1.01
>
>
>
> It is fortunate that I had made a dvd as backup of my photos, so I can
> recover the lost info. This was a good reminder for why it may be good to
> have archive backups! For the sake of a speedy backup, I had switched to
> making backups to an external hard disk. I do this regularly, but don't keep
> archival copies. In this instance, I discovered the problem long after the
> original files had been replaced on the external hard disk. The DVD is what
> saved me!
>
>
>
> My question to the list is in regard to the AccuSoft and LEAD Technologies
> references. Any idea what programs I may have been using that caused my
> image info to be lost? Also, why would such a program destroy such important
> information?
>
>
>
> Peter Shkabara
>
> --------------------------
>
> [log in to unmask]

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