An HDR image is produced by the manipulation of more than one constituent image, all images being of the same subject. The final rendering shows a far greater range of light intensities across the whole picture.
Ever Imaging offer a software application that will control and manipulate all aspects of the required tasks - HDR Darkroom. The current version is 1.2 for Windows. Download is direct from their website and it can be trialled prior to purchase. Many file formats can be used e.g. jpeg, bmp, tiff and camera RAW. Future releases will include a single file enhancement engine for jpeg, bmp, png and tiff files.
The process for producing an HDR image has two major stages. The first is to produce a "Digital HDR Negative" and the second is to "Develop" the negative.
To produce an HDR Negative you select suitable pictures of the subject. They are required to cover as much of the light ranges as possible, i.e. under-exposed, correctly exposed and over-exposed. In practice, these three will give you a good result. In theory, more would be better, but more than five does not seem to significantly improve the result.
The first step is to input the image names, see screen shots below. You are required to select whether the application will align the shots or not. A little extra time is required to align them but it is not significant. I found it was of benefit to always choose this option. However, having used "hand held" images I would suggest you take the advice on the HDR Darkroom website and try to use a tripod when it is possible to do so. I could not get the hand held ones to align and considered if a manual alignment tool would be of benefit. I did try one other HDR application and can report that the HDR Darkroom's align tool was much better.
The Tone Mapping stage comes next, and three separate engines are available: Local Tone Balancer, Local Tone Enhancer and Fast Tone Compressor. Each allows for the relevant parameters to be manually adjusted, these being Strength, Local Lighting, Brightness and Saturation. The user can also change the Colour Balance - Cyan-Red, Magenta-Green and Yellow-Blue. The Black Point and White Point can also be clipped. Usefully a Histogram is displayed for Red, Green, Blue and RGB. There are three preset image sizes, and the image can be rotated upto 360 degrees in either direction. A zoom slider allows the final image to be resized on the screen. Saving can be made in one of the following formats - jpeg, bmp, tiff, png, hdr, exr and tif (48 bpp).
A Batch Processing facility exists that can process batches of images, but there must be the same number of images input for each of the HDR images to be output. This number being set within the "HDR Darkroom Batch Window" (see screen shot below). It also allows for the selection of the input file location (only one per batch), the output file location and whether it is to be saved as a jpg or HDR image. Again, the alignment can be automated or left as the natural position of the images when input. The exposure can be set to EXIF or Guess and finally the Tone Mapping can be chosen as Local Tone Balancer, Local Tone Enhancer and Fast Tone Compressor. Each of these has a "Setting" button that allows full manual control over each of the values referred to above e.g. lighting and post processing settings, see screen shot below. Finally, a useful progress bar is provided.
The HDR Darkroom site contains two sets of files for use as a part of the tutorial and also contains a useful Support Centre and Forum page. Many good examples of HDR images can be found on the HDR Darkroom website.
This application is a delight to use, it is intuitive and fast. The user’s progress through the production of the HDR image is clearly mapped and reported. HDR images are fascinating and can be much more evocative than the standard pictures that make them up. I would recommend HDR Darkroom as being an excellent introduction to this area of image manipulation.
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