HDR Image Processing

HDR, or High Dynamic Range Image Processing is an interesting technique for reproducing images that would otherwise be impossible, specifically those that can’t be captured normally because the dynamic range is too wide for the recording media — be it film or digital capture.

— from cblee - (?)

The basic idea of the technique is pretty simple. Bracket three exposures of the scene (in very quick succession), and composite them in an image editor. One image is exposed for the mid-tones, one for shadows and one for highlights. From what I’ve seen lately, most people are working with about two stops difference between each exposure (ie: two stops under-exposed, normal exposure and two stops over-exposed). The example above, by Chris Lee, clearly shows the three original images, and the HDR processed result.

– from i-marco - (?)

It has been suggested that the technique can be “faked” in digital photography when shooting RAW by making exposure adjustments to the RAW image, saving out the variations, and then applying the HDR process to those images. I’m not sure how well that would work, but, it’s certainly worth fooling with for images that have already been made. This also assumes that the dynamic range of the original scene is not too drastic. The image at left, by Marco van Hylckama Vlieg was made from a single RAW file.

The detail in some of these images is astounding, even on displays that have a relatively limited contrast ratio.

There are several groups on flickr that focus on HDR imaging, including one that shows “before and after” images so you can really see what the difference is.

I’ve been fooling around with this for a couple of years now digitally, with varying degrees of success, but don’t really have anything worth showing at the moment. That, however, will be sure to change!