James Stephens

This post describes a simple and effective technique for producing an image with higher dynamic range from two differently exposed images using Adobe Photoshop CS2. It is amenable to use with jpeg images so you don’t have to shoot in RAW to use it.

This technique is not the same as the high dynamic range (HDR) capability recently incorporated into Adobe Photoshop CS2. Adobe Photoshop CS2 has a Merge to HDR function which can be used to create an HDR image from a series of differently exposed images encompassing the entire dynamic range of a scene. However, my experience has been that using it requires considerable skill to produce good results, as well as a good measure of patience and disk space since the computationally intensive operations necessary to generate an HDR image should really be conducted on 16 bits/channel images that may easily consume 100MB.

Let’s begin with an example of what can be achieved:

Blended Multiple Exposure
Canon EOS 300D with 28-135 f/3.5-5.6 IS lens @ ISO 100
(click image to enlarge)

The above image was created from these two shots:

Exposed for the highlights
Canon EOS 300D with 28-135 f/3.5-5.6 IS lens @ ISO 100
(click image to enlarge)

Exposed for the Shadows
Canon EOS 300D with 28-135 f/3.5-5.6 IS lens @ ISO 100
(click image to enlarge)

Technique

Capture

Using a tripod, capture two images of the scene, one exposed for the highlights (underexposed) and one exposed for the shadows (overexposed). Ideally one should use Aperture Priority combined with a cable release and the Auto Exposure Bracketing (AEB) capability to capture images perhaps two stops apart typically (e.g. -2,0,+2). The median image is not required. For each image check the histogram to make sure that there is no highlight clipping in the underexposed image or shadow clipping in the overexposed image. AEB ensures that you don’t have to touch the camera between shots as this would disturb the alignment betwen images. Depending on the histogram you may have to reshoot. Try to use mirror lock-up.

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