Broadening your range: How to create High Dynamic Range (HDR) images from a single exposure

Home

Tutorials

HDR Tutorial

Closeup of an HDR image of a laughing Kookaburra

High Dynamic Range Imaging (HDRI) allows one to produce some of the most breathtaking images that you can imagine. The problem with digital cameras is that they are very limited in the range of colours and tones that they can capture in a single frame. This is true for all digital cameras, no matter how advanced and how expensive they are.

HDR allows a photographer to subject their subjects to multiple exposure levels thereby allowing their cameras to assimilate as much colour information as possible at each of those different exposures. Combining them correctly results in breathtaking images that are otherwise nearly impossible to produce with a single exposure.

This tutorial provides a primer on how to create HDR images.

In image processing, computer graphics and photography, high dynamic range imaging (HDRI) is a set of techniques that allows a greater dynamic range of exposures (the range of values between light and dark areas) than normal digital imaging techniques. The intention of HDRI is to accurately represent the wide range of intensity levels found in real scenes ranging from direct sunlight to shadows.

-Wikipedia.org The tools that were used in this tutorial are:

Adobe Photoshop CS2 or better.
Photomatix Pro version 2.5 or better.

It is worth noting here that the primary image from where we are going to generate our HDR image MUST IDEALLY BE SHOT IN RAW. There is a reason for this that we are about to get into. HDR is typically best for images that are completely still. Why is this? HDR images are created by combining a series of images shot at different exposures. In order to keeping ghosting at a minimum, we want to keep our subject as consistent and still as possible. Hence, HDR is typically not suitable for high speed motion and windy days.

The technique being discussed here, however, manages to get past that. Hence the need for images to be shot in RAW. RAW files come with an extension of CR2. Generally speaking, most point-and-shoot cameras do not have RAW functionality. A typical Canon or Nikon SLR however will have RAW functionality. Our first order of business is to open the RAW file in Adobe Photoshop's RAW converter. Note the image below, and the highlighted area bounded by the red rectangle.

Creating the set of differentially exposed images

The image in its original format is correctly exposed. The slider bar in the highlighted area will allow you to change the exposure to desired levels. Using the slider bar, set the exposure settings to -1.00, -0.66, -0.33, 0, +0.33, +0.66, and +1.00. For each exposure setting, save a copy of the generated file in a folder. JPG formats are fine, but do not use any compression. Save the files in their maximum size and quality. I recommend using a consistent file naming structure such as "HDRSOURCE_x.JPG" where 'x' is a sequence number (consider starting at 0 and working your way up). If you've done this correctly, you should have generated for yourself a set of images as shown below:

The set of differentially exposed images

Once having done this, we are done with Photoshop. Go ahead and close it out, and open up Photomatix Pro. Click on the Generate HDR Image button, select all the images that you just saved and hit OK. The screenshot below displays the interface that you should see. I've used version 3.0 of Photomatix Pro while creating this tutorial.

Opening up the source images in Photomatix Pro

We're getting close to generating our HDR image now. Once the images load, an interface similar to the one shown below should open up.

The Photomatix Pro interface will load each of the differentially exposed images into the dialog box. It offers you the option of allowing Photomatix to automatically assign the exposures, or for you to manually set the exposures in.

In my experience, I've found that Photomatix Pro does quite a good job in detecting the exposures of each of the images automatically. Occasionally, on the correctly exposed image, you will see an exposure that looks something like 5.966666664E-8. If you're an engineer or someone with a strong math background, you can skip to the next paragraph. For anyone who might be confused on this matter, relax. This expression is approximately equivalent to the numerical value of 6 divided by 100,000,000... pretty close to zero!

Now, if you're concerned about any of the values of the exposures in the images loaded, you can click on each of the exposure values and manually change them to the values. In this example, our values range from -1.00 to +1.00 in steps of 0.33 (or 1/3rd).

Once you're ready, go ahead and hit the OK button. The following dialog box will appear.

This dialog box will allow you to set the parameters under which Photomatix Pro will attempt to generate the HDR image. Note that since we are using differentially exposed versions of the same original RAW image, there is no need to compensate for ghosting artefacts. Likewise, alignment of the images is a non-issue too.

Once you hit OK, Photomatix Pro is going to take a little time to process the image, and should eventually present you with a screen similar to the one below.

Now, at this point, the image isn't what you were hoping for. The colours all seem to be a little overdone, and the image is a little... eughh!!! Don't panic. We are not quite done yet. As the left hand side of the image shows, a regular monitor is not capable of showing the complete range of colours of an HDR image. We need to do a little tone-mapping before we can get a dramatic looking HDR image. Click on the Tone Mapping button. The following dialog box will display.

Once again, note the highlighted area bounded in red in the Details Enhancer tab. The two sliders here for Strength and Color Saturation will allow you to adjust your image to the colour tones that you desire. A lot of photographers like to see more vivid tones, while others stay away from overdoing it. At the end of the day, it's a matter of taste and preference. I recommend setting the Light Smoothing value to Very High. This permits a more natural transition among brights and darks. The final image in this tutorial is shown below and illustrates the difference between a standard range image, and a high dynamic range image.

Before and after... the image on the left is the original; the one on the right is the generated HDR image.

HDRI allows a digital photographer to capture a much larger range of highlights, midtones and shadows. Most digital cameras are all capable of capturing the entire range... just not all at once! This post processing technique allows you to bring out the vividness in images.

In closing, HDRI is best used for images shot in optimum lighting, and are typically suited to inanimate objects. I do not recommend using it for night-time photography as this technique tends to introduce a lot of noise into the finished image. I also do not recommend using it for portraits, as it tends to bring out a lot of the flaws that are naturally present in the average individual's skin.

15% off Photomatix

Use DoubleConvex as your discount coupon code on the HDRSoft website to get 15% off your purchase of Photomatix Pro with a free upgrade from Version 3.0 to Version 4.0 when released.

Tutorials

Featured tutorial: Conveying Motion - choosing the correct aperture and shutter-speed.

View all tutorials.

Postcards

Latest postcard design, and buy postcards from our Zazzle Store.

Click here to browse all our postcards available through our Zazzle store.

Limited Editions

Latest limited edition print: Still waters run deep.

Click here to view all our limited editions.

15% off Topaz Adjust

Use DoubleConvex as your discount coupon code on the Topaz Labs website to get 15% off your purchase of any of their products. Save more when you get the Topaz Photoshop Bundle.

HDR Workflow

Check out the HDR Workflows Video. This series of videos covers DoubleConvex's choice of workflow step-by-step from taking the image from the camera to a finished image.