High Dynamic Range

It’s too long since I added to this blog, but the summer and autumn seem to have gone by in a whirl and suddenly it’s winter again. Our first fall of snow on the Pennines came on Tuesday…by Wednesday the sun was out and the snow was thawing…so I made a quick decision to take some time off and dash out with my camera to capture the snow before it disappeared completely.

When I arrived at The Manns, the light under the cloudless blue sky was very strong and contrast range very high. The danger, in these conditions, is that either the highlights will blow out or shadows will block up, so I decided to try some HDR shots.

The principle is simple….take at least 3 shots, one an average for the scene, one a stop over exposed and one a stop under. (In retrospect, I might have tried 5 shots and bracketed even more.) The files are then downloaded and openend in PhotoMatix Pro…a clever little bit of software which merges the differently exposed photographs into one image with increased dynamic range; stage two of the process, tone mapping, reveals detail in both highlight and shadow areas.

Here is an example: The three original exposures,1 stop under, “average metered” and one stop over, with the blended tone mapped composite below.

The merged and tone-mapped result.

Shadow and highlight detail are improved…the tone mapping has revealed much more depth of colour in the sky and the colour of the grasses and trees is much richer.On the whole I think it is an improvement on the original, though it certainly doesn’t have a “natural” feel to it.

My second example is from Dovestone Reservoir.

The merged and tone-mapped result:

Here, the HDR software has done a good job, creating a more richly coloured image and handling the moving birds very well, without ghosting effects.