Image Stacker

Image Stacker. Image Stacker combines multiple images into a single image. It can be used to overcome one of the last remaining limitations of digital cameras compared to their film counterparts: their inability to take very long exposures. Image Stacker can also be used to reduce the appearance of "digital noise" in images created by digital cameras or scanners, and create "synthesized long-exposures" without overexposure.

Why stack images? Good question! It depends what you are trying to achieve. One of the most common reasons is to take images of very faint objects that are barely discernable in any single image. By "stacking" several images together, you can create a "synthesized long exposure" that is brighter than any of the individual source images. For example, if your digital camera is limited to taking images with exposures of 30 seconds or less, it is impossible to take pictures of a moonlight landscape which typically require exposures of a few minutes. However, if you take six exposures (each of 30 seconds) and then stack them together, you can create a synthesized 3 minute exposure.

Single image

Five images stacked together

Another reason for stacking is to take pictures of star-trails...capturing the motion of the stars as they travel across the night sky. Such images require exposures of several minutes to several hours, which are not possible with most of today's digital cameras. (Image Stacker also includes a special blending mode (the Brighten mode) that works particularly well for taking images of star-trails in light-polluted areas.)

Another important use for Image Stacker is to average images together. Unlike stacking, where the intensities of each source image are added together, averaging images does not create a brighter image. Instead, the averaging process dramatically reduces the appearance of random noise in digital images. Random noise looks very similar to grain in film images and is most apparent in areas of uniform color such as blue skies. Averaging several exposures of the same scene (or scans of the same negative/slide) can produce a much smoother, natural looking image. Image Stacker can also perform dark-frame subtraction to reduce the appearance of non-random noise.

More information and sample images. For more information, Image Stacker's documentation is available here, as well as a gallery of sample images produced using Image Stacker.

Screenshot. Image Stacker is distributed in two forms, a Windows version (pictured below) and a DOS version that can be run from the command prompt and incorporated into scripts and batch files.

Image Stacker Main Screen

Distribution Status. Image Stacker is distributed as shareware, meaning you are expected to "register" it (i.e. pay $17) to purchase the program. While Image Stacker will operate without registration, it is limited to processing 10 images with sizes no larger than 640x480 pixels. Image Stacker comes with no warranty and TawbaWare and the author take no responsibility for any damages caused by the use of this program.