Merge to HDR in Photoshop CS2  

You may have heard some talks about Dynamic range, the dynamic range of a certain digital camera and the ways to adjust it in your pictures. When talking about Dynamic range, we talk about the range of brightness levels that exist in a certain picture. It represents the levels of the smallest and largest possible values, from a step beyond complete black and a step before complete white. Before proceeding with the tutorial in Photoshop itself, some initial information about a dynamic range and the camera’s ability to capture its full extent.

The Dynamic or exposure range of a certain digital camera is measured in “stops” (a stop representing either a doubling, either a halving of the amount of light received by the camera’s sensor or film). In order to capture an image full of detail both in its darker parts, as well as in its lights parts, a photographic camera must capture as much dynamic range as it can. Today’s modern sensors found in digital cameras can acquire a satisfactory amount of dynamic range; there are cases, such as landscape photography, where more exposure range is needed to fully capture the details.

You can achieve this in different ways: through hardware means, adding split neutral filters in front of the lens, but this can be quite expensive. Another way of getting more dynamic range from a scene is to take multiple exposures of the same image (you will only need to vary only the shutter speed most of the time). Take the normal shot and then take some more shots at 1-2 steps under and after that initial normal shot. All you have to do then is to go to Photoshop and blend these images to get a final picture with more dynamic range than the normal shot.

This is done in Adobe Photoshop CS2 with its HDR (High Dynamic Range) implementation. After you add the images taken at different stops let the software use its internal algorithms to generate an image with a far greater dynamic range.

In order to produce a HDR image, you need to have taken enough pictures with different level of exposure, both under- and over- exposed, so that the software will have enough information available to create the final image. Adobe Photoshop recommends before using its HDR tool to have at least three-four images, with a recommended five to seven. When taking all those shots with the camera, be sure to have them with one or two stops apart. Do not modify the camera’s aperture when taking the pictures as you will modify the depth of field. Take the images with different values of the exposure time.

We will take for example a series of seven pictures of a sunset. When opened in Photoshop, they will appear as ranging from -2 to +2.7 stops under and above the 0EV (normal exposure setting). You can see that in some of them you can clearly distinguish the ground details, while the sky is overexposed, and in others you can clearly see the colors of the sunset sky. What you want from the final HDR image is to have both the details of the foreground, but not to lose the beautiful colors of the sky.

Below are a series of steps which you guide you in using the Merge to HDR tool in Photoshop CS2.

Before stating editing the images, copy all the shots taken which you want to merge into a HDR image in a separate folder, so you will not mix them with other pictures.

If you have used a digital camera which can take images in the RAW file format, you will need to transform the RAW files into TIFF or PSD file formats. In order to keep all the information available in the RAW file, it is recommended to keep the pictures in 16 bit mode during processing. However, you your camera’s resolution is very big you will end up with several files each having even 100MB, so if your machine does not have enough hardware resources, you may need to downscale them.