IPTC non destructive tagging

[MIRAV]

Hello,  and thank you for accepting me in this forum.

I would like to have an simple and definitive answer to a question I see a lot of different
answers on the web.

When you open a jpg and just edit the IPTC core (adding copyright, title,  caption, and keywords) is it destructive for the image ?

Some people say no, because it doesn't touch the image but others say that it will destruct when you save your changes, in photoshop for example, after editing the iptc in File Info.

How it is with Photo Mechanics ? Does it alter the image to tag the file ? Does the tags are embedded in the image IPTC and readable by others applicationbs than PM ? Can I tag today and add other tags tomorrow and retag next week my image totally lossless ? 

Thanks for your answers.

[Kirk Baker]

Photo Mechanic edits metadata without modifying the image data of JPEGs.  You can edit a JPEG with Photo Mechanic as many times as you like and it will never modify the image data.  You can even strip out the metadata with Photo Mechanic and there will be no modification to the image data.

Photoshop definitely does modify the image data when changing metadata.

-Kirk