backdate a picture

[suso]

Hi!!
I'm a new member, so sorry if i post something you already talked about!
And sorry for my english too!!

I have a photo shoot in 2011 and i would like that it result shoot in 2010. Nobody have to recognize it!
Is it possible?
Can somebody help me or do it for me? i'm really really clumsy with programming or something like this.....

Thank you for your help!

Best!!
S.

[JanK]

Yes you need Exiftool.

exiftool "-AllDates-=YY:MM:DD HH:MM:SS" *.jpg

In your case
exiftool "-AllDates-=1:00:00 00:00:00" *.jpg

This change DateTimeOriginal, CreateDate, ModifyDate. After this use the following to set the FileModifyDate correct.
exiftool "-DateTimeOriginal>FileModifyDate" *.jpg

[BogdanH]

Hi Susanna,
Just jumping in, to welcome you on ExifTool forum. I can see, you allready got answer -as I have promised
Not important in this case, but it might be worth to mention (for future), that you're using Mac.

Bogdan

[suso]

Thank you!
I'll try asap!

Hope it will be simple as you told me....

Just last question: is it possible to recognize that i change the date? is there something (for e.g. firmware version or some other code string/data) that can explain this jock?

Thank you again, you are really really kind!

Best,
S.

[Phil Harvey]

Hi Susanna,

I'm not sure exactly what you are asking, but if you add the -v2 option to the command you will see more details about what ExifTool is doing when it updates the file(s).

- Phil

[suso]

thank you Phil,
i just want that a picture results shooted one year before the really shooting.
But i need that there aren't in the data-file any details that can show i modified the date.
For eg: if i shoot in 2011 i have xxxx firmware, instead in 2010 i had xx firmware.
This is one example i know, but i don't know if there are some others; or if the data code, data string, has a different type of writing year by year.

Thanks again!

Ps: thank you Bogdan, yes you are correct! i had to tell i work with mac...

[JanK]

Yes the Exif Version 2.3 was released on Apr. 26, 2010 so when you set an image with Exif Version 2.3 from this year back to a date from the last year that is before this date (or better before a date on which the camera you use was supporting this Exif Version) they could wonder about that. The Version is listed in "[EXIF:ExifIFD]  ExifVersion"
And the Firmware is saved in the Metadata ([MakerNotes:Canon] CanonFirmwareVersion, [MakerNotes:Canon] FirmwareRevision,...). You should check if this was available on the date you change the photo too.

Canon has a ImageUniqueID in the MakerNotes. I don't know what it can say.

Futhermore you should check the Metadate if there are any Makernotes which belongs to the date and are not change by AllDate. In the fact you are using OSX with the change of the Dates the Create Date is also changed. That is not done by Windows.

So please don't lie don't betray someone and use it in the right way.

[BogdanH]

Hi,
As I see that now, the question is, is it possible to change metadata so nobody can recognize that. As JanK pointed out, there are many catchs -especially because some metadata sections in Makernotes are still unknown.
So, I would say... I still think it is possible, but there can't be any guarantee... and without being 100% sure, it is actually not possible... That is, I could "convince" my friends and perhaps even Phil Harvey ( ), but not the court or Canon.

Bogdan

[Phil Harvey]

It may be interesting to note that I can tell by looking at the file structure if ExifTool has been used to modify a file.

- Phil

[JanK]

Wow. How that?
Now I'm interested.

[Phil Harvey]

All cameras have quirks in the way they format the EXIF/TIFF information.  Leaving empty space, overlapping values, out-of-order IFD entries, values on odd-byte boundaries, discontiguous or non-sequntial value data, missing next-IFD pointers, etc.

ExifTool will fix all of these quirks and problems when it updates EXIF/TIFF information in a file.

- Phil

[suso]

Thank you!
I think i'll not do anything.
But it was a pleasure to find this forum and this program.
You are really really kind and available!
So thank you so much!

And.... have a nice Christmas!
See you!

Best,
S.

[Phil Harvey]

It may be interesting to note that I can tell by looking at the file structure if ExifTool has been used to modify a file.

Out of interest, I just thought of a simple way to tell if it was likely that exiftool has modified the EXIF or XMP of an image:

EXIF:  exiftool -tagsfromfile @ -exif:exifversion FILE

XMP: exiftool -tagsfromfile @ -xmptoolkit FILE

If the above command doesn't write the file ("0 image files updated"), then it is likely that the file doesn't contain the corresponding metadata.  In this case, ExifTool may have been used to delete the metadata, but was probably not used to write it (because ExifTool writes the ExifVersion and XMPToolkit tags by default).

If the command does write the file, and the file does not change (use a "diff" or "md5" utility to determine if the file changed), then it is very likely (I'd guess > 95% chance) that this type of metadata (EXIF or XMP) was last edited with ExifTool.

Conversely, if the command does write the file, but the file is changed (different md5), then it is very unlikely (< 5% chance) that ExifTool was used to last edit the file.

This should be a valid test across a wide range of ExifTool versions because the structure of the metadata as written by ExifTool hasn't changed in quite a while.

- Phil