The Canon 17-40mm f/4.0 L lens is a great lens for architectural photography and real estate. It’s very wide and cheaper than the 16-35mm f/2.8. And since most architectural photography is shot from a tripod, we don’t need the extra stop of light. That is not to say it doesn’t have its flaws, because it certainly does.
The lens has barrel distortion (see below)! With today’s softwares it’s easy to fix and Lightroom or Camera Raw does a great job – illustrated to the right. This shot was a single image with no additional lighting required and minimal post production. Using your cameras histogram you can see when the scene has too much dynamic range. However, this scene was handled quite well by the 5D MII and with minimal post production almost all of the detail was preserved.
Before
Here you can see the severe barrel distortion of the Canon 17-40mm f/4.0 lens. The cyan guide lines help illustrate the warping. Because the image is shot in RAW, the floor highlights and back wall detail can be retrieved.
After
This image has been corrected and the barrel distortion removed. This can be done in many softwares or using Camera RAW. I've also corrected the colors and tones of the image to more accurately depict what the eye sees when in the space.