HDR imaging, the proverbial crown jewel of photography tricks, has been limited to those using Adobe Photoshop for too long. For about three months now I have been researching the best freeware way to create HDR images. For those who do not know what HDR means, it stands for High Dynamic Range, which is a method of photography that attempts to capture more of the light spectrum than a traditional image. Using samples from the high and low end of the light spectrum, HDR is a digital composite of many different images at different exposures. Creating an HDR image is a complicated process, one that usually takes no less than half an hour to churn out one photo, and on top of this, your images can never be appreciated in their 64-bit native color depth because of the computer industry’s failing to upgrade monitor standards. If you are willing to put the time and effort into achieving a beautifully detailed image that HDR spits out, then pay close attention.

What you need

Creating an HDR image does not require highly-sophisticated equipment as one would think. Basically any camera with an adjustable exposure value (EV) setting can be used and will churn out a beautiful image. This is what makes HDR imaging so great; even those of us who can not afford a $600 USD Nikon camera can still create some stunning pictures. Heres the short list of what you need to make an HDR image:

• A tripod
• Any digital camera with an adjustable EV setting
• A computer (Mac OS X, Windows, or Linux)
• A method of transferring the pictures to the computer (cameras typically include a USB cable)

If you have all of these, then you only need to download one more thing: QTPFSGUI. QTPFSGUI is a freeware HDR rendering program, and as a bonus, it also handles tone mapping. Tone mapping is like icing a cake, it takes your HDR image and makes it beautiful (more info). QTPFSGUI is the only freeware HDR renderer that includes built in auto image aligning and tone mapping, and there is a version available for Mac OS X, WIndows, or Linux. After you have QTPFSGUI installed, you are ready to go and capture your images.

How HDR works

So you have all of your basic essentials for creating an astounding HDR image; now it’s time to start snapping photos. Most cameras that have adjustable EV settings allow only a certain range of EV, which is generally from -2EV to +2EV. The reason you need to know this is because an HDR image is not just one image, it’s not just a single snap on the camera and into the computer. It’s anywhere from three to thirteen snaps before you’re even ready to think about going to your computer. The reason why HDR images look so astounding is because they have anywhere from three to thirteen times the amount of light range that a standard image does; the larger the light range, the less grain there is in a photo, the more the human eye can be drawn to the photo, and the more lifelike the image appears. There is also a slight drawback to HDR imaging.

The HDR paradox

There are several ground rules for shooting the base images for your HDR image. First, you can never use your camera’s flash. The flash changes the amount of light outside of the cameras iris, and ultimately standardizes it. This causes your HDR image to not have any dynamic range at all. A constant light source, such as a light bulb, can be used, because it does not create a standard ground of image brightness. Second, your camera needs to be anchored to a very firm position, as any movement between the base images will cause ghosting in the final HDR image. This is where the HDR paradox appears. How can HDR imaging be considered a form of photography if it is incapable of capturing movement? HDR imaging is indeed incapable of capturing a moving subject. Any movement in between the base images completely ruins the final HDR composite. However, this is not the first time that a method of photography was incapable of capturing movement. In 1826, the first photographic process was invented, and the images took over eight hours to fully expose. These images required no movement of the subject, or else ghosting would occur. Ghosting is where a part of the image has moved and appears as a ghostlike figure in the final image. I am sure that eventually HDR imaging will be able to capture movement, however it still wrestles with the original problem that photography itself faced over 200 years ago.

Capturing Your Base Images

The most important part of the HDR image creation process is the capturing of your base images. When I first started experimenting with HDR photography over a year ago, I was only using a base three HDR process. A base three HDR process uses only three base images for the creation of the HDR composite. These three are the three essentials on the EV scale: -2EV, 0EV and +2EV. The diagram to the right shows the difference between the three images. Be sure that for every EV variation you capture you also capture the opposite EV variation (e.g. -1.8 and +1.8, etc...) An HDR image created out of three base images yields three times the dynamic range of a standard image. Now that I have had some experience with HDR photography, I generally shoot base thirteen HDR composites. These yield thirteen times the dynamic range of a standard image. If you are shooting a thirteen base HDR, your base image collection will look something like this:

Off to Renderland

Now that we have all of our base images captured, it’s time to open up our HDR rendering software. (For the purposes of this tutorial we are using QTPFSGUI.) Open up QTPFSGUI and select “New HDR.” A window will pop up and prompt you to select your base images. After adding all your base images into the program, select “Auto Align Images” from the right hand side of this dialog window. From the drop down below the auto align button select “Median Threshold Bitmap.” After a moment a window will appear; if you selected “Auto Align,” you can go ahead and hit “Next.” If you did not select “Auto Align,” you will need to use this window to align your images. After the alignment window, you will see another dialog appear asking for the settings of HDR creation. The defaults have always worked for me, and anti-ghosting always causes crashes so I just use the defaults.

Tone mapping

Tone mapping is one heck of a trial-by-error game. There are a whole lot of settings in QTPFSGUI’s tone mapping section and it would take days to describe them all, so my advice is to play around with it, and get a feel for what the different settings do.

You are done!

Finally you have finished your HDR image! It may have taken a while to do so, but I think it’s worth it. What can you do with it though? There is no point in just letting it stagnate on your hard drive. My advice is to get a Deviant Art account; they offer a non-destructive uploader, so your HDR images will look just as pretty once you have them on Deviant Art.

Links

Download QTPFSGUI
My Final HDR For This Article
Deviant Art