Digital Outback Photo
- Photography using Digital SLRs

 

Workflow Technique #064

Using Metadata in Your Workflow
Part 1

article by Veit Irtenkauf

 
 
Whenever you take a picture with a camera, or scan a slide, the firmware of your camera or your scanner captures not just the actual image itself, but also additional data, describing the environment in which the image was taken. This data is called metadata and its understanding and utilization can be an invaluable aid in your workflow.

Part 1 of this series evaluates the use of EXIF metadata. Part 2 will introduce you to IPTC metadata integration in your workflow and will also discuss other forms of metadata.

EXIF Metadata

EXIF (Exchangeable Image File Format) is the most commonly used type of metadata. EXIF is a standard controlled by the Japan Electronics and Information Technologies Industries Association (JEITA). It is currently in revision 2.2 (also called EXIF Print) and supported by most camera manufacturers.

Almost all modern digital cameras support EXIF today by storing specific information about each image you take, such as aperture, exposure time or focal length. Many software programs support EXIF as well, and some have implemented advanced functionality based on EXIF data. Adobe Photoshop CS, Capture One Pro or ACDsee automatically rotate your pictures, if they were taken in portrait format, while others modify during the transfer from the camera to your computer the time stamp of your image file to reflect the date, when the shot was taken and not when it was copied from the camera to your hard drive.

In fact, the simplest consumer-oriented workflow would not be feasible without the use of EXIF data: Shoot an image with your point-and shoot camera, do some in-camera “auto-tweaking” of the image, take out the memory card, put it into a printer, and then view, select and print your 4x6 snapshots. The printer can read such settings as White Balance or Color Space from the EXIF information of an image, allowing for further in-printer adjustments before the image is then printed.

For professional and serious hobbyist photographers, understanding and utilizing EXIF data can be a very powerful part of our workflow. It can be so helpful that I would urge you to seriously reconsider using any software that does not support EXIF. Personally, support for EXIF is a “must have” criterion whenever I evaluate new software for my workflow.

Accessing EXIF Data

EXIF data is typically treated as attributes of an image, so the first place to look is the properties of an image (ALT-Enter in many Windows programs). Adobe Photoshop displays EXIF information in the Metadata section in the lower left corner of the File Browser, as well as in the File/ File Info dialog (click on Advanced, then expand the EXIF section).



Photoshop CS File Browser reports EXIF information that is easy to interpret


Evaluating The Quality Of EXIF Data

Displaying EXIF data in any program will always yield the same result, right? I had never given this too much thought, so I took a few test shots to find out. The answer it: Not exactly! It depends on the camera and its age (and thus, what EXIF specification was used when the camera’s firmware was developed) and on the EXIF implementation by the software maker.

I took my test shots with both my relatively new Canon 300D and my 2+ years old Canon Powershot G3. I shot both JPG and RAW and all images were taken in P-mode which means using Evaluative Metering, with White Balance set to Auto. Then I looked at the EXIF information of these images in 5 different software programs:


• Adobe Photoshop CS
• BreezeBrowser PRO 1.01
• Irfanview 3.95
• ThumbsPlus 7
• Extensis Portfolio 7

For the Canon 300D, a relatively new camera system, the results were pretty much as expected. All programs not only covered the basics well, such as exposure time, exposure correction and focal length, but also handled more advanced information such as white balance or metering and exposure modes. The only exception is Photoshop CS : While its File Browser reported the information the way I expected it, Photoshop itself reported only raw data under File Info. While I could probably compute an aperture value of 262144/65536 as 4.0, I have no clue what a metering mode 5 is or why the shutter speed value of my image was negative. I hope Adobe will eventually provide more legible information, or provides a preference setting, so I could switch to the same information as in Photoshop’s File Browser.



Photoshop CS File Info only reports raw EXIF data that you need to interpret on your own.

For images from my 2+ year-old Canon Powershot G3, the results are quite interesting: While all software packages get the basics right, such as focal length, exposure time or exposure correction, the results differ significantly for some of the more advanced functions where camera specific information is needed. Example: White Balance which was set to “Auto” and was correctly identified for the 300D images. For my images from the G3, Photoshop reported “1”, Photoshop File Browser, Irfanview and ThumbsPlus reported it as “Manual” , while Portfolio and BreezeBrowser do not report it at all (interestingly, Breeze Sys’ Downloader PRO reports it, but as “Daylight”). So all 5 got it wrong.


Incorporating EXIF Into Your Workflow

EXIF metadata is always generated by your camera and is stored in the header of each image you take regardless of the format (typical formats supported by cameras today are RAW, JPEG and, in some cases, TIF). Since there is no need to alter the EXIF data if an image, even if you work on the image itself during your workflow, most software programs treat EXIF data as read-only data and do not allow you to change it.

However, as the example of the shots taken with an older camera shows, there is a certain need of interpretation that you have to do on your own. Therefore, I recommend the following steps in your workflow

1. Analyze where in your workflow you typically need to access EXIF information and what software you use for it.


ThumsPlus 7’s display of EXIF data could use some rounding algorithms

2. For that software, check the quality of the EXIF data for all cameras that you use. For older ones you might have to develop a “translation sheet” per camera, so you know that “Metering Mode = Pattern” really means that the metering mode was evaluative and not center-weighted. I highly recommend creating your own translation sheet per camera, printing it and maybe even taping it to your monitor, so you have it handy when you need it.

3. If your software program allows you to change the EXIF information of an image (very few do), you might want to consider doing it.

4. Alternatively, there’s software that allows you to extract EXIF information to regular text files. While there’s a multitude of programs that allows you to extract the information for an individual shot, I know only two that allow you to batch-extract them. ImageMagick works fine on Windows, Macintosh and Linux, although its user interface is quite complicated, since it is a command line utility. The other one is Breeze System’s Downloader Pro which allows for extraction of EXIF information when downloading images from your memory card.




Downloader Pro uses EXIF data to set the timestamp of downloaded images and allows for extraction of all EXIF data to external text files

5. I find having access to extracted EXIF information very useful, since it gives me a uniform view of the EXIF data of all my images that I can access at any time and any stage of my workflow. It always looks the same, I always know where to look for it, I know what values are listed where in a file, they are in plain English and thus readable. In short, it makes my life easier, and that’s what a workflow is all about.



Extracted EXIF data: Always same format, thus easier to read


Workflow Considerations For Scanned Images

Film cameras do not store EXIF data, so when you scan negatives or slides, your scanner stores only scan-specific EXIF metadata, such as the date of the scan and not the date when you took the image. While this might not be too much of an issue, it might present a problem when cataloguing your image. Thus, some cataloguing software, such as Extensis’ Portfolio 7, allow you to change EXIF data. For archiving scanned images, this is a very helpful feature, assuming you still have the data from when you took the image.


Extensis Portfolio 7: Changing the EXIF metadata for Date/Time when an image was taken

However, if you plan on changing EXIF data for many images at a time, you need batch capabilities as well. Unfortunately, I have not found any software that supports batch-altering of EXIF data.

Editor's note: A reader brought to our attention that a program called Exifer seems to allow some batch settings of EXIF data.

“Normalizing” EXIF Data Between Camera Formats?

Do you shoot in just one format? Most likely not. While I shoot predominantly with my DSLR, I always carry my trusted Canon Powershot G3 and often snap pictures with it, and even if it is just for location scouting or as a reminder of a potential setup. Often, I end up with pictures from both cameras at the end of a photo shoot. Obviously, each image has the EXIF information from the camera it was taken with. But since these cameras use different sensor types and lenses, their EXIF data cannot directly be compared. As an example, while the G3’s focal length of its zoom lens is 7.2 – 28.8mm, its equivalent in 35mm terms is 35-140mm, so a 28.8mm shot on a G3 is not a wide-angle, but a tele shot. Does this mean I need to “normalize” (change) my EXIF data to 35mm equivalents? Only you can answer that question, but personally, I don’t think it is worth the effort. But it is another example why you need to look at the EXIF data of an image in the context of the camera, which it was taken with.

Conclusion

EXIF metadata is always at your fingertips, thus providing you with valuable information during every step of your workflow. However, the EXIF metadata of an image needs to be interpreted within the context of the camera/scanner which it was taken/scanned with and thus its correct use isn’t necessarily a “no brainer”. It requires some initial evaluation time to understand its potential and use in your workflow. But once you determined how to read and utilize it best, EXIF metadata becomes an even more powerful source of information to you and your workflow.


Stay tuned for Part 2 of this series, which will cover IPTC and other metadata.

 
 
 

   

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