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Producing Realistic Images with High Dynamic Range (Part 1 - Part 2 - Part 3 - Part 4)

Dynamic range is the range of light that can be captured in an image, from the darkest shadows to the brightest highlights. Due to hardware limitations, however, cameras can only capture a limited dynamic range when photographing in tricky lighting conditions. For example, when you take landscape shots of a mountain beneath a clear blue sky, the photos come out far different from how your eyes see it. The resulting photos either have good exposure of the mountain but with an almost-white sky or have a blue sky but with unrecognizable dark portions. To produce a more realistic image in these situations, the common practice is to apply complicated, tedious, and time-consuming traditional photography techniques.

PhotoImpact, always on the prowl for better solutions to your photography woes, now has a High Dynamic Range feature. This feature compensates for camera system limitations and tries to resolve exposure problems that photographers frequently encounter when shooting scenes that contain dramatic differences between light and shades. It produces an optimized image by combining different copies of the same scene and uses different exposure levels to extend its perceivable tonal range. To produce such an image, multiple shots with different exposures are first combined into a High Dynamic Range (HDR) image that will record the complete tonal information combined from all the shots. This information is then used to produce a final optimized image.

Photo shots taken with different exposures.

High Dynamic Range uses a set of images
to produce a more realistic photo like this.

In this tutorial, three images will be used with varying exposures as source images to illustrate how to use High Dynamic Range.

Creating a Camera Curve Profile
When using High Dynamic Range to optimize images, you first need to generate a camera response curve for your camera. A camera response curve indicates how the camera’s light sensor responds to different light intensity levels. A camera response curve must be saved as a camera curve profile. Since the sensitivity to light of sensors in digital cameras varies, you have to save a camera curve profile for each digital camera you use. You can apply a camera curve profile to optimize single-shot images or to an image with subjects in motion such as the splash of water or a running river.

Note: PhotoImpact includes preset camera curve profiles for some digital camera models. If there is a camera curve profile available for your camera, you may use it without the need to create a new one

Step One:
To create a camera curve profile, open the source images taken under different exposure settings. Ideally, five or more source images are required to produce a camera curve profile. Nonetheless, for illustration purposes, this tutorial will use only three images. For guidelines on how to bracket your shots, read the section entitled “Bracketing Your Shots”.

In this example, three shots of a scenic ocean view were taken inside a covered porch. Notice that each photo contains different tonal ranges because of the different exposure settings.

The three photos have different details on the highlight, midtone, and shadow areas. The first sample image shows some details along the front arch and well-saturated green leaves outside the railings. The higher midtones in the second shot reflect perfect blue skies but half of the image area is shaded black. In the last image, the shadow areas were properly exposed which made the brick wall finishing visible. This inversely affected the highlight areas. It washed out the clouds and the small island on the view.

Sample 1 has intense shadows.

Sample 2 has increased midtones.

In Sample 3, highlights are washed out.

When you create your own camera curve profile, make sure that you use source images with a wide exposure difference among the highlights, midtones and shadows, just like the sample images, to obtain a better reading of the camera response curve.

Step Two:
Select Format: High Dynamic Range.

Step Three:
In the HDR Composition tab, select Auto generate from the Camera curve profile drop-down menu.

Step Four:
Since the sample photos are Exchangeable Image Files (EXIF), the F-stop interval will be automatically calculated based on the recorded exposure values. EXIF photos record all the exposure settings that you used to capture the shot. But if you use non-EXIF images, you need to manually specify the F-stop interval from 0.1 to 10. Generally, using an F-stop interval of 1 to 1.5 produces an optimal result.


Step Five:
Click Compose to create the camera response curve.

Note: If you use images with identical exposure values, you will be prompted to remove them. In the Image List Panel, select one of the identical thumbnail images then click to remove one. Retain the other one to create a camera curve profile.

Step Six:
The program automatically opens the Optimization tab. Click the HDR Composition tab to go back.

Step Seven:
Click Save camera curve profile. Save the camera curve profile using your camera’s brand and model name. Saved camera curve profiles are added in the camera curve profile list. You can use it the next time you want to optimize images that were taken with the same camera.

(Part 1 - Part 2 - Part 3 - Part 4)

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