Datasheet

9
Working with Digital Images
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Following are the steps to convert from 32-bpc HDR to 16- or 8-bpc:
1. Choose Image ➪ Mode ➪ 16 Bits/Channel or 8 Bits/Channel.
2. Make sure the Preview box is checked and choose one of the following four methods
for adjusting the brightness and contrast in the image until the image’s appearance
and tonal range meets your requirements:
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Exposure and Gamma. Move the Exposure slider to adjust the gain, and move the
Gamma (midtone) slider to adjust the contrast. If the result is acceptable, click OK to
complete the conversion.
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Highlight Compression. This is an automatic method that compresses the highlight
values in the HDR image so they fall within the range the lower bit depth can support.
If the result is acceptable, click OK to complete the conversion.
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Equalize Histogram. This is an automatic method that compresses the dynamic range
of the HDR image while trying to preserve some contrast. If the result is acceptable,
click OK to complete the conversion.
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Local Adaptation. Move the radius slider to specify the size of the local brightness
regions. Move the threshold slider to specify how far apart two pixels’ tonal values
must be before they are no longer part of the same brightness region. You can also use
the toning curve to make adjustments. It’s usually best to uncheck the corner option
so the curve will be smooth. (For more about using curves, see Chapter 11.) If the
result is acceptable, click OK to complete the conversion.
NOTE
NOTE
With the HDR dialog box open, you can use the Save or Load button to save or load
your custom HDR conversion settings.
Tips for Taking Photos for Merging to HDR
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Use a tripod.
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Take at least five to seven photos to capture the dynamic range of the scene.
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Vary the shutter speed to create different exposures. (Caution: Changing the aperture can
produce lower quality, and changing the ISO or aperture may cause noise or vignetting.)
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Keep in mind that auto-bracketing may not provide enough differences in exposures.
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Set exposure differences one or two EV (exposure value) steps apart (equivalent to about
one or two f-stops).
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Don’t vary the lighting in the images.
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Keep each photo identical except for exposure. The scene must be stationary.