High Dynamic Range

Cameras are generally only capable of capturing a relatively limited range of "luminances" (gradations of brightness). This can often leave photographs feeling "flat" when compared to the original subject because the human eye is capable of perceiving more variance in the light and dark areas.

High Dynamic Range (HDR) is an imaging technique that aims to counteract this effect. It can be used on still subjects to infuse a greater sense of color and depth into your photos.

HDR is generally accomplished by taking multiple photographs of a single subject at different exposure levels. This works best if you use a tripod, and a camera with a good manual mode. Ideally, your camera supports exposure bracketing- a camera mode that automatically takes a few pictures at different exposure levels.

Underexposed	Original	Overexposed

For instance, my wife's Canon has an exposure bracketing mode that takes 3 shots at one time. It allows you to specify a range, and then it takes a photo at the current exposure setting, and one at the high and low ends of the selected range.

To make my HDR images, I took several "brackets", to get a wider sample set. This is only really possible if your subject isn't moving at all.

If your camera does not have exposure bracketing, you can still work with a completely still subject. Set the camera to manual mode, and then take several photos, each with a different shutter speed, while keeping the other settings the same.

The end result will be a set of photos, all essentially the same except for the shutter speed used to capture each one.

Unless your camera is super fancy and has built-in HDR functionality, that is. Some cameras can take the next step and combine those photos for you on board. My Casio, for instance, has a limited ability to combine multiple shots into a single image.

High-Speed Lighting Mode	Automatic Landscape Mode	Low-Light Mode

The Casio EX-FH100 has a few different modes that will combine images taken at high-speed using different exposure settings. One of them is meant for scenes with variable brightness- such as someone sitting in front of a well-lit window. Another mode is meant for low-light settings (without using a flash).

While neither camera mode really creates a true HDR image, I thought it was still worth mentioning. In my opinion, the camera's automatic "landscape" mode made for a prettier picture in this case, but you can be the judge. Under some circumstances, these modes work really well.

Using HDR creation software gives you complete control over how your photos are combined. Some quick Google searching will reveal a couple of good sites that list free HDR creation software. Gizmo's Freeware boasts the best collection of free HDR software, but I found this page on the Panotools wiki to be more informative. Your mileage may vary depending on the software you choose, so try a few of them out and pick whichever seems to work best for you.

The only tool I have personally used for HDR is Adobe Photoshop, so until I get the chance to try out other software this tutorial will only go over Photoshop.

Creating an HDR Image in Photoshop

Photoshop has a built-in automation feature for creating an HDR photo that is surprisingly easy to use.

Begin by opening up all of your images in Photoshop. The easiest way to do this is to select them all in Finder and drag them to the Photoshop icon.

Your images will open up. By default, in CS5, they will open in tabs- your behavior may vary depending on settings and version, but the overall process should be about the same.

To start the HDR automation tool, select "Merge to HDR (Pro") from the "Automate" menu, under "File".

Photoshop will ask you which files you want to use- select "Add Open Files" to bring in all of the files you've loaded.

You should see your images load into the HDR dialog. Select "OK" to proceed.

After some thinking, Photoshop will bring up this screen. You will see all of your photos, sorted by shutter speed, and a preview of the HDR result.

You can play around with the various presets and options until you get a look you like. The different presets can produce some drastically different results. Unfortunately, you can't save multiple files from here. You must repeat this entire process to create images using the different presets.

Surrealistic	More Saturation	Default Settings

When you're happy with the preview, hit "Ok" and wait a while. Photoshop will perform a series of automated tasks, combining, aligning and cropping your images to produce the final result. You can continue to modify the image in Photoshop, or simply save it as is.

Try to find some nice, still subject matter with good contrast- and snap away! Take as many photos as you can, this will give you the most flexibility once you get back to your computer. Good luck, and have fun!

If you are interested in learning a little more about HDR, I posted a follow-up shortly after writing this post. Continue reading to learn more about the technical aspects of HDR, and how to save your image before rendering it.