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QTVR Panoramas - Implications of Image Capture, cont'd

Choice of Image Resolution on the Size of the Panorama

Most developers use 35mm film to capture images for a QTVR panorama. Developers using film generally use Kodak's PhotoCD conversion process to digitize the source images from film to a digital format. The PhotoCD process creates five digital images for each negative on a roll of film, all at 72 dpi (dots per inch):

• 192 x 128 pixels
• 384 x 256 pixels
• 768 x 512 pixels
• 1536 x 1024 pixels
• 3072 x 2048 pixels

Although the size of the images (in number of pixels as well as file size) varies greatly, the same view is represented for each negative.

PhotoCD Image Resolutions

For the sake of conserving space in the graphic, only the four lowest resolution levels are represented here.

However, the higher resolutions provide for greater depth of detail in the digital image. To visualize the relationship of the PhotoCD image's resolution size to the size of the QTVR panoramic Pict, imagine that each successive resolution is twice as far from the camera.

Panorama cylinder size relationship to source image resolution

Naturally, as the resolution size increases, the resulting QTVR panoramic Pict's file size also increases. Larger file sizes have two direct implications:

• more hard disk space and RAM memory will be required during development
• for good playback performance, faster machines (especially video bus speed) will be better for the ultimate users

If the source images are digitized using any other process, you should convert them to the standard monitor resolution (72 dpi) before proceeding with QTVR development.

Currently, most QTVR developers use source images at the 768 x 512 resolution. These create final QTVR panoramas in the neighborhood of 500-800 kilobytes in size (depending on the lens used) and provide adequate playback performance even on lower end machines. The resulting QTVR panoramic Picts can be downsized in a pixel editing program, such as Adobe Photoshop, to create even smaller versions for playback in demanding environments such as on the world wide web.

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