Helping people with computers... one answer at a time.
Photographs often include additional embedded information about the picture. Most is boring camera stuff but a couple of items are worth knowing about.
I am curious: how much information is made available to someone if I send a photo through email (if any at all)? For example, if I attach a photo through a provider such as Yahoo!, can the receiver of that photo find out any information about my computer or me? I know my IP address is viewable in the email - but I am curious about the photo.
More than you think, but most of it's pretty boring. And none of it is about the computer.
I'll set aside the obvious fact that whatever's in the photo is part of what you're sharing. That's the point, after all.
But modern digital photos often include a lot of additional information you might not realize is present.
Let's start with this innocuous photo of a puppy I shot just a few days ago:
I'm showing you the picture as it's hosted on Flickr, a popular photo-sharing site.
If you click on that photo, you'll see some links on the lower right:
Right away you can see when I took it, and what camera I happened to use.
Click on "More properties".
As you can see, there's a long, long list of information about the photo.
What you're seeing is the "EXIF" information that's included with the photo. From the site:
Almost all new digital cameras save JPEG (jpg) files with EXIF (Exchangeable Image File) data. Camera settings and scene information are recorded by the camera into the image file. Examples of stored information are shutter speed, date and time, focal length, exposure compensation, metering pattern and if a flash was used.
Now, most of the information seems pretty innocuous, and not really worth being concerned about, unless you're trying to hide the kind of camera you're using, or the fact that you edited the photo in PhotoShop (which, in this case, I did), or other photographic details.
There's one piece of information that, while currently rare, is likely to become more common in the near future.
Some cameras are starting to include GPS receivers that allow them to record the location a photo was taken.
Is that something you care about? I can't say.
But if that photograph of you on a business trip to Philadelphia turns out to be tagged as being taken in Honolulu ... perhaps you will.