Every photograph has a particular dynamic range, which is a collection of pixels where the starting point is the lowest brightness value, and the ending point is the highest brightness value, such that the photograph is clearly defined among the range. Thus, the wider dynamic range, the more information included. Suppose we need to shot a house when the landscape/sky has big difference of the lowest and highest brightness (which happens frequently with real estate photography). We easily fall into 2 extreme cases, which are either the house is clear but the sky is “extremely white”, or the sky is well defined but the house is only black. That is because the dynamic range of the photo is much wider than what the camera sensor can take in one single photo. Then, in those cases, the HDR shooting comes into effect.
High Dynamic Range (HDR) is the technique to extend the brightness range a camera can take in one single photo, by taking multiple photos at different setting of brightness range. The common set of photos is 3 ambient exposures, along with 1-2 flash exposures (we will discuss about flash exposures in another article). Now this discussion will focus on how to bring out the best quality of the HDR shots through post-processing in some photo editing software.
Firstly, the 3 ambient exposures should be set up such that they will be used as follows:
One well-exposed photo (EV = 0): can be taken as the base layer because all the normal details which can be seen by human eyes are included in this exposure.
One under-exposed photo (EV < 0): in this photo, the sky or light source will be blown out, so we need to get rid of them. What we take is only the main objects, which should be walls of a house for exteriors, or home furniture for interiors.
One over-exposed photo (EV > 0): this exposure brings the blown-out information in the under-exposed photo back to final edits. Now we are fine with taking the sky or the light source into the base layer because the camera sensor will define those details very well.
Note the EV setting is only a representative parameter, photographers need to adjust much more properties of the camera to get the desired shots. It is very long story of how to set them up efficiently, but that is not the topic of this discussion. Suppose that we all have very nice exposures, now we are talking about how to merge them together to get the best final photo.
The next step is to import the exposures into HDR blending software. There are so many programs have that function. The general principle is to have a base layer well defined at the main area of the house, and then merge in all the uncleared details from the other 2 exposures. During the process, there are few steps the editor needs to pay more attention to, since they could easily make mistakes when doing them:
Overall looks of the photo: Almost real estate photography avoid yellow light and yellow wooden floor in the final product, because that color is considered as unpleasant when it is used for commercial purposes.
Window bracketing (or other over-exposed areas): We do not often have nice simple shaped windows, instead, patterned windows are more common. As a result, many details on the windows need to be taken back after the whole window is bracketed. It is because the light going through the window screen is from outside, but the light reflected from the details is from inside, we need to take the two light sources from two different exposure. In case that we forgot to take the details back, the window looks very contrasted and unrealistic.
Sky/lawn replacement: When we do cloning on some area of the photo, we easily make it inconsistent with the remaining of the photo, since we get the cloned materials from outside the photo. So one problem is we need to take care of the brightness and colors consistence, and other problem is how to take back the details on the edge of the replaced area. If there is a tree at the edges, we might lose some green in the tree leaves. So be careful when doing soft brush there.
There are still few things about the preference of each photographers that can be taken into account when editing an real estate photograph. For example, regarding the window view from interiors, some want it to be well defined, others want to blow it out to get more focus on the interiors alone. Despite the yellow light and floor are not expected in real estate photography but it still appear somewhere when they want to bring out a warm and cozy atmosphere inside the house. To conclude, except some basic standards in the blending process, editing styles and requirements can vary widely, which any good editors and good editing team need to be able fit themselves into.
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