On Sat, Nov 29, 2014 at 11:07 AM, Izack Varsanno <[email protected]> wrote:
> I'm sure that the guys that wrote exiftool knows what they are doing.

If they've implemented write support for raw files they're going down
a dangerous path.

> It is not that hard to update a RAW file without breaking it. even if you
> change the length of specific fields.

Having worked with most of these formats I strongly disagree with
this. Since the whole file uses absolute offsets if you change the
length of a field somewhere you would have to change every single
offset in the file that points to a location after that. Since we
don't understand the file completely we can't be sure we've changed
all those offsets. Later when you use some other or newer software to
extract more information from the file (e.g., some extra metadata to
know the focus settings) you'll find out you broke it.

> In the site I pointed to, they have a table that tells for every RAW type,
> which field they know to read only and which to read and write.

I haven't looked at the code but hopefully they only edit fields that
have fixed width. This is probably the case here as exif often has a
large field with a NUL terminated string and then some extra garbage.

> Anyway, as I suggested, a backup is a good practice.

The only sane way to deal with raw files is to treat them as
read-only. So I agree with the backup just so you can go back to the
original file and forget you ever edited it :)

Cheers,

Pedro

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