Played 
It's been a while since I put anything on this site that isn't of a technical nature so I thought I'd throw something photography-related up here. Today's non-technical article is about HDR photography, i.e. the practice of combining multiple exposures to create a single high dynamic range or HDR image. Here's what I came up with.
Before I start, I'll just say that this is just playing about with HDR - an actual attempt would probably produce much better results. :)
To make the images in this post I used a tripod-mounted Nikon D300 digital SLR camera w/ remote shutter release. Although you *can* take the exposures necessary for HDR by hand-holding your camera it's not recommended because all exposures must be of the same scene if you want to get the best results. A digital SLR camera or compact with the ability to control both shutter speed and aperture is required. The aperture must be set the same for all exposures to prevent parts of scene becoming 'blurred' due to depth-of-field changes. The ability to control shutter speed is necessary as HDR photography requires you to bracket your exposures, usually by +/- 2 stops. In case you don't want to read the Wikipedia article linked to just there, bracketing is taking a 'master' exposure and (usually) adjusting the shutter speed up and down a certain number of stops so that you have a set of shots of the same scene but with a range of varying shutter speeds.
A typical bracketing sequence with the shutter speed being adjusted by 1 stop each time might be like this (note that the aperture doesn't change). The ordering of these shots is irrelevant - it's the order my camera is set to though.
- 1/125 f/4.5 - the 'master' image, correctly exposed.
- 1/60 f/4.5 (-1 full stop)
- 1/80 f/4.5 (-2/3 stop)
- 1/100 f/4.5 (-1/3 stop)
- 1/160 f/4.5 (+1/3 stop)
- 1/200 f/4.5 (+2/3 stop)
- 1/250 f/4.5 (+1 stop)
With those shots taken it was a case of loading them into Photomatix Pro, a trial version of which can be downloaded from HDRsoft. The tone-mapping preferences are very much user- and image-specific so I won't list them here. The HDRsoft team has made a couple of good tutorials available to get you started if you've never used Photomatix Pro before.
Here is one of the exposures in my set without any post-processing being done. I shoot RAW and obviously this shot could be cleaned up and improved a lot by using ACR, Lightroom or whatever your RAW-processing software of choice happens to be. Personally I use Adobe Photoshop Lightroom.
And here is the same scene but as an HDR composite made up of 7 bracketed frames. The colour of the water and the detail in the clouds are pretty crazy I reckon ...
I've got the same 2 images combined into a single image so they can be seen side-by-side too - check it out.
it's available on Flickr for those interested in seeing it.
Obviously scene choice plays a big part in how well an HDR image comes out (the one above is just to demonstrate results, not photography) but it's still good fun. :)