HDR or High Dynamic Range is a photographic technique I have been experimenting with for the last few months. The technique involves taking several shots of the same scene at varying shutter speeds and then blending them together in the computer. The technique works on images where there is a wide range of lighting levels appearing in the shot and beyond the ability of the camera to record the image without either under exposing or over exposing parts of the image. For example taking a photograph in a ruined building on a bright sunny day the shadow areas will be at least 3 or 4 stops darker than the sky. If you expose for the sky the shadows will lose detail. If you expose for the shadows the sky will bleach out. HDR offers the opportunity to end up with both extremes perfectly exposed in the same shot.
What do you need? Camera and a steady tripod and a ‘high dynamic range’ view.
Set your ISO rating to 100 and your aperture to f22. Compose your shot using the Aperture mode noting the shutter speed that the camera selected. Take a frame and look at the result. What you’re looking for are the areas that are under exposed and over exposed. Next set your camera to manual and select the shutter speed that your Aperture mode shot dictated. This is your middle exposure setting.
Next you are going to take a series of shots of exactly the same view but at different shutter speeds. Its important that you don’t disturb the tripod or you’ll experience problems when you try to blend the images later.
I’ve found that taking the shots using the timer allows the camera to settle and ensures better results.
Start by increasing the shutter speed from your middle exposure in increments of one stop. Examine each frame until you arrive at a shot where the sky is perfectly exposed. Return to your middle exposure setting and this time decrease the shutter speed in increments until you arrive at a frame where the shadows are correctly exposed.
For some shots this may be a total of 4 frames for others it could be a total of 8 frames.
The best programme to merge the frames is called Photomatix. The trial version allows you to make a HDR image but you will have their logo in your shot.
The programme will work with Tiffs or JPGs. The simplest way is to click on ‘Batch Bracketed Photos’ select individual photos, load in your bracketed exposures for your first composition, select one of the presets or use the default setting and press run.
The programme will take each photo, identify the correctly exposed parts and merge them with other parts of the other frames creating a perfectly exposed HDR image.
Some examples of my own experiments with HDR are below.
A good reference book to learn the technique is ‘Understanding HDR Photography’ by David Taylor – Ammonite Press ISBN 978 1 90770 854 1.