I love the HDR photos I’ve been taking the last few weeks, and in searching through various Flickr groups I found a nice little technique for mixing time lapse and HDR photography.
There are several ways of recording the passage of time in a photograph, an inherently static form. One is to use a long (or bulb) exposure, keeping the shutter open for a few seconds or minutes. These produce those classic ‘car lights at night‘ type photos. The other is to keep the shutter open, but expose the image periodically with a flash, catching moments in time rather than a constant ‘blur’ of time.
An HDTR image is an image in which multiple frames taken over an arbitrary time interval are blended together. The images in the time-lapse set are merged together by progressively sampling time-adjacent images horizontally or vertically. The difference between an HDTR image and a single-frame long exposure is that the contribution to any region of an HDTR image is primarily from a single image from the time-lapse set, rather than an average of all images.
Depending on how the blending is done, the result is an image in which a strip, row or column, is derived from a specific point in time. If a long exposure frame is a stack of acetates of time, an HDTR is a series of strips of time. The strips can be blended in a variety of ways, generally to limit banding artifacts and produce a smoother time gradient.
I hope to get some of these up within the next few weeks..