EasyHDR
EasyHDR is an image processing program that produces High Dynamic Range images from normal, 24-bit, true color photos taken with a typical digital camera. You can squeeze much more from your camera than you have ever imagined, especially if it does not support saving images in raw mode with 12 or more bits per raw pixel.
But what for do you need high dynamic range images? The answer is very simple. For sure you have tried to take a photo of a scene at very bad lighting conditions, when some parts are shadowed and other are brightly lit. When you want to properly expose the shadows you overexpose the bright areas, and when you want to prevent overexposure you underexpose the dark areas. That is a typical problem in astrophotography. Just try to take an image of our Moon at wide angle. Try to catch the lunar seas as well as some dim stars or clouds. You can see all of that with your own eyes so why can't you take such a photo? Well, all of that is because the response to light of the digital camera sensors is linear. Simply, the dark areas need longer exposure time, but then the brightest parts of a high dynamic range scene are overexposed. Of course in some cameras there are 10 or 12 bit A/D converters and the output 8 bit per channel image is created using LUT (Look Up Table). There is a remedy to that unwanted linearity. You can further alter the photo's luminance scale using curves tool in your image processing software. This allows, for example, to greatly brighten the shadows, while keeping the bright areas not saturated. This method is widely used, but has two major disadvantages: already overexposed parts remain overexposed and the noise level rises.
The idea behind easyHDR is to produce a HDR image from several photos of the same scene taken at different exposure time or f-number. The brightest parts of the scene should be properly exposed in the shortest exposure photo, and the darkest parts should be visible in the longest exposure. The program allows you to change x/y offset between the images to be stacked.
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