by George Taniwaki

If you have ever taken a picture through an exterior window, you may have been disappointed with the results. This can happen either standing inside a building shooting out, or standing on the street shooting in. That’s because if the side you are standing on is brighter than the other side you will get reflection of the lights off the glass. And if you are standing in the light, you will also get the reflection of yourself which just looks goofy.

Another problem is that if it is a sunny day, it will be much brighter outside than inside, so all of the objects inside the building will be too dark relative to the objects outside.

Photographer Nick Kelsh has a blog post where he gives a good description of the problem and some tips to avoid it. Though his recommendation to throw a rock through the window may be a bit extreme.

You can try to fix the problem using Photoshop, but it is a lot of work because you will need to fix the color balance for two different parts of the scene. The interior lighting will probably be an artificial source like incandescent (2700K) or fluorescent (5000K) while the exterior will be lit by the sun (~10,000K). Removing the reflections will be harder still.

A better solution, if you can control the interior lights, is to take two pictures and combine them. The first picture is taken with the lights on and is designed to capture the object inside the building. The second picture is taken with the lights off and is designed to capture the view outside the window. (This assumes the lights are inside.)

Then you merge the two images. If the window is rectangular, you don’t even need fancy equipment and software to perform this trick. In the example I show below, I didn’t use a tripod, just a handheld smartphone. To manipulate the images I used  free Google Picasa to adjust the color balance and brightness of the two images. I copied and pasted the image within the window using free Microsoft Paint.

Take two pictures

The first step is to take two pictures out of the window without moving the camera, one with the lights on and one with the lights off. For this example, I am standing inside the house. When taking the picture with the lights on, I set my focus and exposure to capture the most prominent object(s) inside the house. I ignore the reflections in the window (Fig 1).

Conversely, when taking the picture with the lights off, I set my focus and exposure to capture the view though the window. I ignore the underexposure and poor lighting of objects inside the house (Fig 2).

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Figures 1 and 2. Image with interior lights on (left) and lights off (right)

For best results, you will want to mount the camera on a tripod to eliminate any movement between the two images and any blur caused by long exposure during the lights off photo. However, if the window is rectangular and there is no overlap between objects in the foreground and the window, it doesn’t really matter. In fact, the images don’t even have to be out the same window.

Adjust the brightness and color balance separately

Open each image individually in your favorite photo editor software package. I use Google Picasa because it is free. Set the color balance, brightness, and contrast. I dislike the yellowish tone of photographs taken with incandescent lights and always try to correct them to fluorescent. When taking photos with a low quality camera, such as most smartphones, also apply despeckle and unsharp masking. Save both images.

Copy and paste

You can use Google Picasa to crop an image and copy it to the clipboard. However, it doesn’t appear to have a way to paste the clipboard into an image. Thus, we will merge the two images using free Microsoft Paint. Open the image that has the good view through the window. Create a selection rectangle around the image within the window frame and copy it to the clipboard. Open the image that has the image of objects except the window and paste. If the images don’t overlap properly because they are different sizes, start over and resize the first image to match the second. Save under a new name (so you don’t ruin the original image).

The resulting image (Fig 3) looks pretty good, but it isn’t perfect. First, because I was using a smartphone, the focal length of the lens is very short so the sides of the windows are curved rather than straight. Since I used a rectangular selection to cut and paste, parts of the original window image show through. For instance, you can see the reflection of a light peeking through in the upper right corner of the window.

Second, the gooseneck of the sink faucet is within the rectangular selection so it is too dark.

Finally, since I didn’t use a tripod, there is some movement and the gooseneck of the sink faucet is slightly displaced.

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Figure 3. The merged image, color corrected and cropped

Using Photoshop or other advanced image editor, you can make a better selection. And you don’t have to use the image out the window. Once you have created a mask, you can paste any image into the scene.

All photographs by George Taniwaki

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