You’ve been there before. You shoot an image on a bright sunny day and then you realise there’s no detail in another part of the image in the shadows. The basic thing photographers know is that the film/slides/sensor of the camera cannot capture all the exposure values you see with your eye. The eye has a wider latitude to exposure values compared to the camera. So how do you increase the latitude or the dynamic range of the camera? Enter HDR, or High Dynamic Range. This is a fancy term for something photographers have been doing all the time, since the darkroom days. We burn (darken) and dodge (lighten) areas of the picture to pull out the details and to even out the lighting. With the digital camera, our lives are made easier.

The manual method I use a lot is to process the RAW file with different brightness levels, normally one with the right exposure and the other underexposed. I overlay the former on top of the latter in Photoshop and remove the parts of the top layer so that the darker areas from the bottom layer can be seen. I use this for shooting interiors when the outside window lighting is so strong, or when there is insufficient lighting for certain areas. The images above show examples of the final output.

Recently I started trying out the HDR function in photoshop. If you’re using CS3, it’s in File>Automate>Merge to HDR. You would need to have at least 3 images to get a decent merged image. The function allows you to select the number of images, which are then converted into a single 32-bit file. When you want to change to 8-bits or 16-bits, you are required to choose a tonemapping method. The only option that makes sense is the ‘Local Adaptation’ option. However, you may get a file that has so little contrast, it looks comic-like. You would have to increase contrast to make it look real. What you get can be close to what you see in the real world, with a wider dynamic range than just a single shot can give. Here’s a sample image I tried. I shot 5 files with the following exposures -2EV, -1EV, 0, 1EV, +2EV. It was a bright sunny day and the single shot showed a completely washed-out exterior.

You can also merge HDR from a single image. Process your RAW file with different exposures, open all the files in photoshop and then use the HDR function. Of course nothing beats doing it in camera.

One Response to “What is HDR?”

1. Stages in a photographer's life says:

   24/04/2010 at 11:12 am

   [...] our photos increases naturally. And then wham! New advances in software especially in dealing with HDR means you start from scratch with this new understanding – learning to increase the dynamic [...]