Learn About the EXIF Metadata in Your Digital Photos
In this article we present a simple guide to the EXIF
metadata for your digital photos.
Metadata refers to information
that describes the your digital photos—information such as the exposure,
shutter and other settings that you used when you took the picture.
The topic can prove to be confusing to the uninitiated. So
read on, find out more, and soon you'll be handling EXIF like the experts!
EXIF (Exchangeable Image File Format) metadata is pretty much the
standard format in use for most digital photos.
Metadata is not
information that you can 'see' in the same way that you see pixels in your
digital photo. Rather, you’ll need an EXIF viewer or an EXIF launcher to see it.
You’ll benefit greatly from knowing how to interpret this data.
The EXIF information from a digital photo
1. What is EXIF?
EXIF, as stated, is the standard format for
metadata in your digital photos, a standard invented and made popular Japan
Electronics and Information Technologies Industries Association (JEITA).
All digital cameras and major image processing
programs nowadays work with EXIF. Your digital camera remembers the settings you
used to take your picture, such as exposure and focal length, and then stores it
into EXIF format and saves it to your memory stick with your image file.
You can imagine the usefulness of this feature
for a variety of situations where you tweak your photos in-camera. Imagine, for
example, that you crop a picture you’ve taken using the camera’s crop feature.
Your camera stores the information that defines the new cropped image in-camera,
so when you print from the memory stick, it prints the cropped image and not the
original unaltered image.
Metadata make this possible. Likewise, image
processing programs like Adobe Photoshop are designed to work with EXIF metadata
as well to properly reflect any picture adjustments that were made in camera.
2. EXIF Viewers
To interpret this EXIF data, you will need an EXIF viewer. There
are many ways to go about this. Your image processing program should provide
that functionality within the program.
Most
image processing programs will store the EXIF metadata as properties of the
image. Access your photo’s properties, and you should see a tabbed interface,
with one tab indicating metadata. Here you’ll see information such as the Focal
Length, Resolution, White Balance and so forth. Check your image processing
program’s help for information about where your program stores its metadata.
You may be surprised to discover that EXIF metadata isn’t
reported the same way between various cameras and image processing programs. One
program may show that your White Balance is set to 'Auto', for example, while
another program will show some number that you don’t think properly reflects the
original settings. Or these programs will report varying figures depending on
the camera you use.
Field tests have shown this to be true, but we trust in your case
you will stick with one camera and one program. That should eliminate the
headaches.
3. Make Sense of EXIF Information
If, however, you have more than one camera, you may want to take some steps to
make some sense about different EXIF information reported by your program. The
first thing you should understand is that your EXIF metadata is in read-only
format.
The creators of EXIF saw no reason for you to overwrite the information, so it’s
stored in the header of your image file where you won’t be able to touch it.
(Unless you want to hack into it, something we don’t recommend)
Ok, so let’s suppose you have two cameras, and with both you took pictures with
an Auto Focus setting. You open up your image editing program and examine the
photo’s metadata for Camera #1. It reads, correctly, 'Auto'. You then plug in
Camera #2, and it reads '1'. You know that both cameras were set to Auto, so you
have to remind yourself that in Camera #2, 1 means Auto. We recommend that you
create a cheat sheet to keep track of how numbers from one program translate
into another program.
4. Image Editing Programs and EXIF
You have only two other alternatives to create some consistency between
different EXIF information for your two cameras. First, find an image editing
program that actually lets you change the metadata. We don’t know of many major
programs that will let you do this, but it’s worth a try. The second option is
to use software that will extract EXIF information to text files. You might be
able to do this, on a per shot basis, with your existing image editing
application.
There are some better applications to use if you want to extract EXIF
information from a whole batch of images all at once.
ImageMagick is one such program, although it’s probably not user-friendly
since it’s a command line utility. Breeze System’s
Downloader Pro is an easier-to-use Windows program that performs the same
function. The extracted EXIF information in the text file is easier to read, and
if you want to tweak it to achieve consistency in values between your two
cameras, it’s certainly easy to do.
5. Advanced
EXIF Analysis
You can take additional steps to create consistent values from your EXIF
information. For example, you may notice that equivalent focal lengths for
digital cameras and film cameras are noted using different numbers. This may be
a bit disorienting at times if you are trying to relate your digital camera
settings with what you know from the film world.
You can use your EXIF
information to create a lookup, or a database of some sort, to perform the
conversion—if you think it’s worth the effort. It’s up to you. Additionally,
realize that if you get photos from a scanner as opposed to a digital camera,
you will not have the same kind of EXIF information encoded in the final output.
The only metadata stored will be about the scanner, perhaps a date and time
stamp, but little else. A cataloguing program such as Extensis Portfolio 7 will
allow you to alter the EXIF information stored in the images.
Conclusion
We hope this brief guide to EXIF has opened your eyes to the world of metadata,
and shown how useful this can be for you. Whether you use an independent EXIF
viewer or EXIF launcher, this kind of information serves a number of important
purposes.
The digital camera stores all of your photo settings in the header
portion of each image you take. Likewise, image editing programs then interpret
this information so as to accurately reproduce the picture on your computer in
its original dimensions. Finally, you can examine EXIF information and use it to
better analyze and catalogue your pictures.
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