Photographing tricky scenes (HDR)

Digital cameras are amazing but one thing they don’t do particularly well, is cope with scenes where there is significant variance between the bright and dark areas (highlights and shadows). A classic scenario is the landscape photo and the sunset.  Have you ever photographed this type of scene and been left a little disappointed with the results? What normally happens is that the sky looks ok but the foreground looks dark or visa versa – the foreground looks good but the sky is overexposed, too bright and all that lovely detail that your eye saw, is lost. Our eyes and brain are much better at interpreting this type of scene. We have a high dynamic range (HDR) in our natural visual system. Digital cameras don’t however; They operate best where there are no extremes between light and dark. So why is that?

Cameras use metering to measure the amount of light in a scene and then either set or suggest an appropriate exposure depending on whether you’re in automatic or manual mode.  The way a camera meters is limited however! If you want to meter a landscape scene for example, you might set the metering mode to evaluative whereby the camera averages out the light in the entire scene. Alternatively you might use spot metering using a point at the centre of the viewfinder to measure light. With spot metering, you could point the camera at the foreground. The camera would determine the scene to be quite dark and set a bright exposure, or you could point the camera at the sky. The camera would then determine this to be very bright and set a darker exposure. Either way, whatever way you go about it, your final image will either have very dark areas in the foreground (dark areas such as fields) or very bright (blown out) areas in the background (areas such as sky).

One solution, HDR

High Dynamic Range (HDR) is a way to overcome this problem. This involves the photographer taking several exposures (shots) of the same scene. The images are then loaded into a dedicated software program that merges them together extracting the optimum exposed area from each. Typically, a photographer will set the camera on a tripod, set focus, aperture and ISO, then take an average meter reading which might suggest a certain shutter speed. The photographer will now take a range of shots using the shutter to adjust exposure. Typically 5 or 7 shots are taken across a range from under exposed to over exposed. The underexposed shots will render the sky beautifully while the over exposed shots will bring out the foreground. The shots in the middle of the range will render the mid-tones.

Where would the world be without examples

Disclaimer: This is my back garden, not known for it’s scenic beauty but nonetheless a great place to practice HDR:)  I setup the camera on a tripod around 4:30pm this evening. It was already dusk and so a decent landscape was a challenge. I set the ISO to 400, worked for a minute on a quick composition and get the shot in focus. I then put the camera into P mode, and took a meter reading. The camera suggested an exposure of f11 at 1/30th of second. I then put the camera into manual mode and decided I would take 5 or 6 shots at f11 ranging from 1/125th of a second (dark, under exposed) to 1/4 of a second (bright, over exposed). I ended up with the following.

(Click to enlarge)

You can see from the above that the under exposed images retain the detail and contrast in the sky but render the foreground as dark, while the over exposed images render the sky as blown out but retain the details and contrasts contained in the foreground.

When I was done, I came back inside and downloaded one of many HDR software packages. I chose Photomatix as it seems popular with photographers and gets good reviews around the web. The software itself is very easy to use. You just install it, load it, click ‘Generate HDR Image’, load in you range of exposures and from there follow the wizard. I had a few go’s and eventually started to get some nice results from playing around with the presets etc.

The result (click to enlarge)

I think you’ll agree, we have an amazing rendering of all the light range from dark shadows to highlights. You can see the foreground and its detail – it’s no longer a dark silhouette but you can also see the sky and all its glorious tones and details. I like landscapes, particularly sunsets. I met a couple of folks from boards.ie this morning and we went out to Renville to take some shots. The two lads gave me loads of pointers that helped me to produce this article so thanks Mark and Mike for all the help.