Most of the time, I use HDR techniques more for artistic effect than anything else. I love the hyper-textured look I can get with Photomatix and only seldom choose to process the images for a natural look (you can find a couple of “natural” example here and here). This week, however, I have been using HDR to great effect in producing images of the interior of my in-laws’ house for use by their realtor.
Although you may think that taking pictures of the interior of a light and airy home wouldn’t pose a problem, you would be wrong. Even in as light a house as this, the difference between the exposure required to see detail outside, through the windows and the exposure required to retain the detail inside the room is somewhere around 6 stops. Your camera just can’t capture that in a single shot. You can either have great exposure within the room and nasty white, blown-out rectangles for windows, or a great view of the outdoor scene and a dark foreground. In situations like this, HDR comes into its own.
Most of the shots I took of the house used 4 exposures from -4EV to +2EV in 2 stop steps. This gave enough range to capture all the required detail. I tone mapped the results with a lower setting of “strength” and “gamma” than I typically use and with a very much higher “micro-smoothing” yielding results like those you see here.
There is actually one problem here that HDR alone can’t solve. Although we cure the exposure problem, we still have a white balance issue to deal with. One of the first rules of interior photography for real-estate advertising is to ensure that all the lights are turned on. Since most lights are tungsten, you end up with a horrible mix of colour temperatures – warm, “orange” tungsten light inside the house and cooler blue sunlight shining through the windows.
Your eyes don’t worry about this and compensate beautifully but your camera, once again, fails rather miserably. Set your white balance to “tungsten” and your interiors look great but the view through the windows is an unnatural blue hue. Set your white balance to daylight and the exterior view looks wonderful but the interior is extremely orange.
To solve this problem, I produced two versions of each tone mapped images, one using RAW files white balanced for tungsten and the other white balanced for daylight (RAW files are wonderful this way – the white balance isn’t “baked in” so you can change it in Lightroom later). I pulled these two images into Photoshop on separate layers and masked them together to give a natural looking colour balance throughout, taking areas lit predominantly by daylight from the daylight image and areas lit by tungsten lights from the tungsten balanced image. The result, as you can see here, looks very natural and definitely reminds me of the room a whole lot better than any of the single exposures I shot while there.