Datasheet

Welcome to Adobe Photoshop CS4

Part I

CAUTION

Eight-bpc RGB images are sometimes called 24-bit images (8 bits x 3 channels = 24

bits of data for each pixel). This can be confusing. For example, sometimes 8-bpc

RGB images are called 8-bit images and sometimes they are called 24-bit images.

Thirty-two-bpc HDR images can represent the entire dynamic range of the visible world, unlike the

lower bit depths, which can represent only a portion of it. Among the advantages of HDR is that

adjusting its exposure is like adjusting the exposure when photographing a scene in the real world.

Blurs and other real-world lighting effects look realistic in HDR images. Motion pictures, 3-D

work, and some high-end photography are mediums that sometimes use HDR images.

HDR images contain brightness levels that a standard monitor cannot display, so Photoshop lets

you make choices about the appearance of the on-screen preview of HDR images by choosing

View ➪ 32-bit Preview Options.

The Merge to HDR command lets you create HDR images from multiple photographs with differ-

ent exposures, thereby gaining the larger dynamic range that 32-bpc images can support.

Following are the steps to merge multiple images to HDR format:

1. Choose File ➪ Automate ➪ Merge to HDR.

2. In the Merge to HDR dialog box, click Browse, select the images, and click Open.

3. If you held your camera in your hands when you photographed your multiple

images, select the Attempt To Automatically Align Source Images option.

4. Click OK.

5. Set view options by clicking the minus or plus button for zoom in or out, or choose

a view percentage or mode from the pop-up menu below the preview image.

6. (Optional) Select or deselect check boxes under the filmstrip thumbnails to specify

which images to use in the merge.

7. Choose a bit depth from the Bit Depth menu. Choose 32 Bits/Channel if you want the

merged image to store the entire dynamic range of the merged images.

8. Move the slider below the histogram to preview the merged image (this does not

remove any image data). This preview adjustment is stored in the HDR image file and

applied when the image is open. It can be changed later by choosing View ➪ 32-bit

Preview Options.

9. Click OK to create the merged image.

You can convert a 32-bpc HDR image to a 16-bpc or 8-bpc image, but some of the image’s infor-

mation will be lost in the conversion. You will need to make choices about what information to

keep and what to throw away based on what you want the converted image to look like.