Guide to Using HDR Photography for Panoramas and 360 Virtual Tours
What is HDR?
HDR photography (or high dynamic range) is a technique that allows photographers to take the same images at different exposures then merge them to create one image with the best parts of each image. This is especially useful for virtual tours because most Virtual Tours rely on 360-degree perspectives. Often, you will be photographing both towards and against a light source. This would usually mean you have to choose between the two and may end up with dark areas that are too exposed and light spots that are too exposed. HDR allows you to shoot at three or more exposure levels: low, medium, and high, and then blend them together to create the perfect panorama.
What are the cons?
This technique is beneficial, but it has some drawbacks. First, processing times: HDR imagery effectively doubles the number of images that you have, so unless you use top-end equipment (i5+ processors), this will significantly increase post-processing time. Second; ghosting. HDR images are three or more images that were taken in succession. When you are putting together your images, you may notice some movement (e.g., trees moving in the wind or people slipping on a funnily placed banana). This can lead to a grey ghosting effect which can ruin your scene. You will need to use software that supports HDR imagery. Most top-end software does, but it is worth considering, especially if your current software doesn’t.
Should I use HDR imagery for my 360 virtual tours?
I recommend that you first get a Panohead and a tripod if you plan to use HDR. The ghosting from holding the camera in your hand can cause problems during post-processing and may even render your scene untouchable. With a little bit of experimentation, you can create stunning HDR imagery for your virtual tour if you invest in these pieces. The HDR format is an industry-standard for creating high-quality panoramas.
You only need a camera that can adjust the exposure manually to take HDR images. The camera can be placed on a tripod to take multiple photos in different directions. This will create one HDR image. This can be time-consuming, especially for 360 virtual tours where you will need various images to create one HDR image. This can be a time-consuming task if you have more than ten scenes in your virtual tour. I recommend that you invest in a DSLR camera with exposure bracketing if you’re serious about virtual tours. Exposure bracketing allows you to adjust the exposures at three or more levels. The added benefit is that ghosting can be reduced by reducing the time it takes to take the images.
Take HDR images
You will need the camera to set your white balance and manual exposure to take HDR photos for your virtual tour. After I have set up my tripod and camera, I adjust my directions by pointing my camera at the most exposed area of the panorama (the sun if outside, or the brightest light source). The exposure is adjusted until the image is on the dark side. If the sun is fully out, you should be cautious as it can damage the sensor. It is best not to point your camera directly at the sun. If you do, it should only be for a few seconds. After I’ve got the base level to my satisfaction, I adjust the exposure bracketing to at most +2 or -2. Some cameras may not be able to go this far, so you may have to take two bracketed photos. Your camera is now ready to shoot exposure bracketed HDR images. If the sample image takes three pictures per press of the shutter button, then exposure bracketing has been set. Take the same pictures that you would typically take to create a panorama. Depending on how many you take (I usually take between 6-12), you will now have three photos for each of them: one for light, one for regular, and one for dark. To increase stability, set your camera to a 2-second delay. This will reduce ghosting and blurring caused by tripod shake.
HDR and post-processing
Once you have created your HDR panorama images for your virtual tour, you can now stitch them together. You can do this in several ways. You can either use your raw images to create HDR panoramas, or you can use software that supports HDR to stitch them together. Each method has its merits, and I recommend trying them all to see which one you like best. There is software that will make your life easier, no matter what method you choose. Technically, you can use high-end stitching software like PTGui and Panoweaver to stitch images, adjust the exposure, and output an HDR image ready to go for a virtual tour. However, I find the HDR fusion mechanisms in stitching software not as effective as dedicated HDR software. My HDR magic formula involves using PTGui to stitch together the images and then output three panoramas at different exposures. Then, I use reliable HDR software for combining them into one HDR beautifully exposed picture that is ready to be used in my Virtual Tour. Although there are many options available, I recommend Photomatix Pro for its professionalism and quality. It is only a PS60. Happy shooting!