Most real estate photographers are using some form of HDR (High Dynamic Range) image processing. The technique involves shooting a series of photos at different exposures and then blending them together using computer software. Done right, HDR processing can yield beautiful, natural-looking photographs. That's the way I use it.
Here are a series of photos that show why I use HDR and why my HDR processing looks better and more natural.
Finished Image as Delivered
This finished image is a blend of 7 frames blended together with a tool in my post-production software toolkit and then given additional work by hand. Notice that the colors look natural, you can see out the windows to the deck, and the image is neither too dull nor overly saturated.
Straight from the Camera
With a lot of work and many supplementary lights, it's possible to balance interior and exterior lighting in a single exposure, but it takes more time and money than any realtor is willing to invest.
Fully Automated Processing
This version was processed with one of the more popular HDR tools available, using the default settings. Notice that the colors are a little oversaturated and the overall image looks dull and flat.
I see a lot of real estate photos that look something like this version, with oversaturated colors and excess detail enhancement. I don't think it looks very natural and wouldn't deliver a photo like this to a client.