Natural light in real estate photography is both a blessing and a curse. Nothing compares to warm, natural sunlight. It has the perfect color temperature(around 5000 on the Kelvin scale) in its natural state. If lights evenly. It is consistent across a wide area and allows people to see the true color of objects and casts shadows equally on all objects in its path.
The bad thing about natural light is that it does what it wants. Yes it is predictable as to what it will do, but you never know when a rogue cloud will black some or all of your light. Depending on the time of day, it can be harsh and at others, it can take on a hue of whatever it is reflecting off of. This can be good in some cases and bad in others.
The biggest issue with natural light in real estate photography is what it does as it comes through windows into rooms that are darker than the the exterior of the home. Basically all homes. When taking photography, most people want to show how bright and "airy" their home is. This requires capturing as much natural light as possible, which means including windows in the scenes.
When taking pictures with bright windows in them, several factors can make things easy or more difficult. The type of window coverings has a HUGE impact on how a room looks and how difficult it will be to get a good crisp photo.
Clean windows without screens and no blinds, shades or covers are the best. A simple valance to add some color or detail, makes for the best composition. This is not always the case, though.
IMO, the worst window covering are the sheer fabric curtains. The ones that almost resemble women's unmentionables🤫. These coverings not only block the view, they diffuse the light and make properly correcting the photo later, much more difficult, if not impossible. Think of a window being a flash or studio light and putting an umbrella on it to spread the light and soften it.
Solid fabric curtains are very common and very manageable. The only issue with floor length curtains is the shadows they create and the light they block. The prevent the light from spreading perpendicularly from the window, so we end up with a hot spot of a window, bright areas above and below the window and then nearly immediate darkness(depending on the fabric) to the left and right. Also, depending on the fabric and color, they can filter the light casting different tints and hues of light throughout a room.
Regular slatted or venetian blinds are probably the second best option regarding lighting control in a home. They are easily raised to eliminate issues. The can be lowered to block light from spilling out of room into a hallway. They can also be lowered and opened to reduce the spread of light, but still offer a source of illumination. They are also very easily handled in post production. As seen in the image above, they allow light to come in, but can reduce glare and add some detail and texture to an image.
Currently popular, cordless blinds eliminate the need for strings/cords leading to a cleaner looking window. Here is an example:
With all that said, light, or lack of it, will either illuminate or hide what your home has to offer. If what you have to offer is outdated and unmaintained, light will expose these issues. On the other hand, if you have diligently kept up with your home, but you lack the proper light, it will be hidden and could cost you money during the sale of your property.