Virtual Tours and the Elusive Perfect Exposure

I started producing virtual tours about three years ago. Initially I was just curious about the technology utilized to create them, but I quickly saw their value in helping to showcase the work of my architectural firm. Being able to show a client a building from the inside or to place them in the middle of one of our Cleveland Ohio outdoor lifestyle centers seemed like a great use for this media.

Given my background in Ohio real estate development and my interest in photography and “all things technical,” l thought it would be fun to turn my hobby into a real business that combined all of those elements. In Early 2008 I found RealTour Vision and created SGMDesign360.com.

Since I am not a professional photographer, its sometimes a struggle to get perfect exposures for the shots needed to stitch together a great panorama. It was particularly difficult when I first started since I was using a 6 shot setup with an 8mm fisheye lens on a Nikon D200 DSLR. (Four shots horizontally and then one up and one down) Correct exposure was critical and post processing in Photoshop was essential. While I liked the result and the ability to do true spherical immersive images, the time investment in each spin was not practical for typical real estate virtual tours. RTV’s 12 shot method gives me much better quality “out of the box.”

Regardless of the technology used, correct exposure is important. So what is the best way to set the camera? Should you use supplemental light, flash or studio floods? What about white balance? It can be very confusing and there is no one best method for every situation. The following outlines several different methods that can be used to get the right exposure. Experiment and see what works best for your situation.

The trick to creating any panorama is to insure that there is even exposure across the entire set of images. Shooting in automatic or aperture priority mode may result in different exposures for each frame, especially if there are dramatic changes in lighting within the scene. While the individual frames will look good, the contrast between frames can be too much for your blending program to handle effectively. So, what is the best way to shoot these photos? There are several different opinions and everyone does things a bit differently. So, in order to simplify the process, I have outlined a few of the options that I use on a regular basis.

Option I – Consistent Exposure and White Balance

Instead of using one of your cameras automatic modes, try using Manual mode instead. Meter only for the mid-tones in the scene. First, if you are using a digital SLR select an aperture setting that will give you good depth of field. I like a setting of f 8. Since we are on a tripod, we can control the exposure with shutter speed. Scan the entire scene and find the extreme lights and darks then meter for the mid range. Once you know that setting, shoot each picture in the sequence using the same set of exposure settings. You should end up with a well-balanced set of exposures to stitch together. I prefer to use natural lighting, so if I have good ambient light I’ll keep the room lights off or try to have them on the lowest wattage possible. Remember to select the appropriate white balance and keep it the same for every frame in the sequence. Turn off automatic white balance in your camera settings menu.

Option II – Adjusted Exposure

Start by setting up just like Option I and meter for the mid-range condition. Note the exposure setting. For each shot, adjust the shutter speed to provide more or less exposure as needed, but do not vary from the mid range exposure setting by more than a stop or two in either direction. Adjustments should be made relative to the mid-range exposure setting, not the previous shot setting.

Option III – Bracket Exposures

A common way to handle difficult lighting situations is to bracket exposure. By taking a series of shots we can expose for both the highlights and the shadow areas and then combine the images in Photoshop to get the correct blending. Post processing is time consuming, but sometimes it’s absolutely necessary. Fortunately, my Nikon D200 offers several automatic-bracketing options. I find the three shot setting works best. Again, I set up and meter to find my mid-range exposure. I shoot in Aperture Priority mode and let the camera automatically adjust shutter speed to give me a bracketed sequence. The camera will shoot Normal, then Under, then Over at each rotation. Basically, I take three shots at each station, letting the D200 change the settings. Be careful to stay in sequence, rotating before all three shots are taken can cause major problems. Once I have all the shots I have a few options. I can separate the shots into a normal, under and over sequence and then stitch each sequence individually. Save them to high resolution jpg, and bring them into Photoshop to blend them together. I have had little success with Photoshop’s (cs2) HDR process, but have found a nice plug in by Fred Miranda called DRI Pro Plug-in v2.0. I believe it was less than $20.

The second option is to just visually select the images that seem correct and assemble a set to be stitched. This eliminates the need for Photoshop work, but this method is highly dependent on your scene and your ability to visually compile the correct image.

Option IV – Supplemental Lighting

I’m not a big fan of using supplemental lighting for virtual tours, primarily because I am not as well versed in flash photography as I should be and have had difficulty creating clean stitches. I know many people do this without issue, but I struggle with it. I have recently been experimenting with a flash diffuser produced by Gary Fong and have been very pleased with the results. I need to experiment with the diffuser using all of the exposure methods to see which approach gives me the best results. I think this method will solve many of the more common lighting problems that we all encounter. I’ll report my findings next week.

Stephen G. Moluse
Cleveland Virtual Tours
www.sgmdesign360.com

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