Exif data is the meta data stored in image files by most modern digital cameras. It contains information about the shooting situation (shutter speed, aperture, focal length etc.) and a lot of other useful data. Your HDR workflow usually removes this data either completely or partially at one stage or the other. Here, I will show you a way of restoring Exif data after your post-processing is finished.
Why would you want to bother about Exif data?
There are at least five reasons:
- You: Having all the data inside the image lets you quickly inspect the shooting situation and several camera settings. This is a great way to learn from past shoots when you compare this data.
- Your viewers: Let’s face it, HDR junkies like us are very interested in technical information about a photo. We like to see which focal length, shutter speed, aperture, etc. others used to learn something. Make your viewers happy and give them this information.
- Copyright: Exif data (and IPTC data) are a great way to put some copyright information into an image. Use it! (Note however, it can be easily stripped!)
- Geotagging: Information about the location where the image was shot are stored in the Exif data. This offers a whole new way of interacting with your images (when you have the right software). Some cameras put this data into the photos automatically.
- Flickr likes it: Rumor has it that photos that have full Exif data in them are ranked higher in flickr’s interestingness rating.
Requirements and Assumptions
You will need a program called exiftool. It comes together with other software like GeoSetter (a great tool for geotagging your photos), or it can be downloaded here. You will also need basic knowledge about how to use a command shell, because exiftool is a command line program (no fancy Windows or Mac GUI).
We will use the exiftool to replace the (most probably broken) Exif data of your finished HDR image with the correct Exif data from any of the source files (preferably the 0ev exposure).
programs like Photomatix strip certain information (like the shutter speed) from its output since, theoretically, an image merged from three different exposures does not have a shutter speed. Or worse yet, it uses any of the information found in any of the input files while it strips others. I found that this behavior is not very consistent. I find it much more intuitive to just give the final HDR image all the data found in the standard (0ev) exposure. In this way, one can easily infer the data of the remaining exposures.
- Finish any post-processing before starting. Otherwise, you may have to repeat this step in your workflow.
- Open your command shell and type the following:
<exiftool path>exiftool.exe -TagsFromFile <original file> <HDR file>
and press Enter. Note that you may have to adapt this line depending on which operating system you use!
- <exiftool path> is the directory path in which the executable of exiftool can be found.
- <original file> is the file name (with complete path if necessary) of the original 0ev exposure (JPEG and RAW works here).
- <HDR file> is the file name (with path if necessary) of the HDR image you produced.
- After a few seconds, exiftool returns and your HDR image is updated. You can check the data using any more sophisticated image viewer software. ACDSee works well here.
- If your image was shot in portrait orientation and you (or any program in your workflow) have rotated it, you will have to rotate it again, because the orientation is stored in the Exif data and you just replaced it with the original information.
- If you upload to flickr, do not forget to configure your account such that it does not hide the Exif data of your uploads (Option “Hide your EXIF data” under your “Privacy & Permissions” settings). After you uploaded the image, you can quickly access its Exif data by clicking on the camera model information on the photo page right below your name.