Friday, September 3, 2010

Split Light Exterior Exposure

The Whistler construction company Peak Ventures asked me to photograph this townhouse that they had done a major renovation on for their Georgie Awards (which are like the Oscars for BC home builders) 2010 submissions. I spent a day photographing the inside of the unit earlier in the summer, and had done a photo of the outside in early morning light. The exterior shot was okay, but because of the location of the unit, it never really got good natural light on the front of it, so they asked me to come back and do a dusk shot of the unit. This is one of the most technical photos you can do as an architectural photographer, as you need it light enough to see the details of the buildings, but you also want it dark enough for the lighting to show up, and in this case, as I was looking almost due west, dark enough in the sky so that the building isn't totally silhouetted. What you do is take a series of exposures as it gets darker, the first where it's light enough to see the details in the building, and then later as it gets darker to get the effect of the interior lighting. Once you have a series of shots with the proper exposures, you combine them in Photoshop to make one exposure. This is what's called a split light exposure.

Here's the set up for the shot. It's very important that the camera is absolutely still throughout the series of photos, or 'in registration' in technical photo speak. I locked the camera down on a heavy Gitzo tripod, and then tethered it to my portable computer. Nikon has software that controls the settings of the camera from the computer, rather than the camera itself. That way I can change the shutter speed without touching, and possibly moving the camera. The step ladder makes a handy computer stand.

The tri-coloured thing is a white balance target that I can use to accurately adjust the camera's white balance. The darker it gets, the more of a blue cast the light picks up, so you have to do constant white balance checks to ensure accurate colour.

This is my 28mm PC shift lens. It's a critical tool for keeping accurate perspective on the rising lines. If you tilt the camera back, it will make the rising lines on the building converge together and make it seem like the building is leaning backward. With the PC lens, you keep the camera parallel to the building, and shift the lens up instead.

Just for kicks, here's what the place looked like before the renovation.

Tech Stuff
Camera: Nikon D700
Lens: 28mm PC f/3.5

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