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EXIF: What Your Digital Images (Pictures) Reveal

1639 Views 5 Replies 5 Participants Last post by  VolGrad
Modern day digital cameras are computers that capture images through normal camera lenses. Unlike film cameras, digital cameras use a digital sensor to convert captured images into standard computer formats. The most popular digital image format is JPEG. JPEG images files have the file extension ".jpg" in the Windows world.

Photographers like to have the exposure information they used to capture an image. They want to know what camera settings (time, f-stop, etc.) they used to take a picture, so they can determine the best settings to use when taking similar photos. In the old film days, this amounted to taking written notes on sheets of paper that indexed to each picture.

Since cameras are computers, they also have the ability to capture and preserve data that interests photographers. It was very easy to program cameras to save all the camera shooting settings and include them inside a standard ".jpg" file. Now it would be easy for photographers to record data from their photoshoots without writing anything down.

After a while, it became apparent that a standard way of formatting this data inside a JPEG file was required. That way, any standard image viewer could display this camera settings data. Thus, EXIF was born.

EXIF stands for EXchangeable Image File Format. It's kind of a slushy acronym. EXIF is a format that defines the structure for adding meta-data information inside JPEG image files. Meta-data is basically data about data.

Through time, more and more computer programs and operating systems have become aware of the EXIF data stored inside JPEG images. Windows 7 can decode this information and catalogs it so users can use it to search for their pictures with it. You could search for all images with a date of 11-20-2010 for instance.

So, what information is stored by digital cameras. Well, it depends on the digital camera. Although the EXIF format has a wide variety of possible parameters, not all cameras use them.

How can you see what EXIF information your camera stores inside your images/pictures? There are several ways to do this. One is to add an EXIF plug-in to your browser so you can right click on an image ansd select EXIT. The browser will pop up a dialog wit h all the EXIF properties the program can decipher. If you use FireFox for a browser, here's a link to the EXIF plug-in I use:

It's called FxIF. It stands for FireFox EXIF and displays the EXIF information for an image viewed with FireFox. Here's an example of what you might find when displaying the EXIF info inside an image on the 'Net:

You can see that most of the information found in the EXIF information for this example image is camera stuff... shutter speeds... aperture... BUT... This EXIF data also includes GPS data for the location where the picture was shot. It even includes a link to display a map image for the location where the picture was taken. Could someone find you using that GPS information? I don't know because I turn off the ability to determine GPS locations in my cameras.

Executive Summary: If you don't want people trying to find your location from pictures you have posted on the Web, disable the GPS settings in your camera. It's just that simple. How do you know if your camera has the ability to store GPS location data? You might have to read through the instructions. An easier way is to download the free Irfanview image viewer and just look through your images. Irfanview shows many more parameters that the browser based add-ons.

EXIF GPS information was added to new cameras as a feature. It makes it easy for a photographer to find out where he took a particular picture. If your camera is a few years old, or was very cheap, it probably doesn't have the ability to discern GPS locations... but you might want to check to make sure!
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Good tip. After reading, I remembered that my Canon G10 has that feature.
Thank you __jb. Great write up, easy to understand and follow. Appreciate the link which I have already downloaded.
Thanks for the info jb
Glad it helped... Photography has been one of my hobbies for quite a while... I used to shoot a few weddings and portraits, but don't do much formal stuff any more.

Here's a link to the Irfanview image viewer I mentioned:

It's free and also an excellent image/picture viewer. I've been a Photoshop beta tester for the last few versions and have always continued to use Irfanview as a simple, fast image viewer. Press "E" while viewing an image and Irfanview will pop up a dialog with all the EXIF information in it.
Great info. Thanks for sharing. Technology is scary good.
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