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11 Making Virtual Reality Images

One of the most exciting new possibilities of Digital Photography   is  the making of images where the point of view or direction of vision can be altered.
This type of imagery is called "Virtual Reality" (VR) as it creates the effect of having an movable object  in front of, or surrounding the person viewing the image. Such images must be displayed on a computer screen so as to allow the control of the point of view by means of the mouse.

Creating convincing VR images requires several specific techniques and is dependant on the use of a camera which has certain essential features if the end results are to be beliveable.

  • Exposure lock - All VR images are created from a sequence of individual pictures. It is vital that each picture has the same exposure conditions so that as the observer's point of view changes, the illuminatiuon of object and background remains consistent. The E-900 features an auto-exposure lock which ensures that the pictures taken in a sequence all have an identical exposure setting.
  • Zoom -  when taking panoramic VR, a wideangle lens allows a complete rotation to be captured in just a few images (about 8 with the E-900 at the widest angle setting) at the risk of vertical lines being distorted and not matching from image to image. Zooming in (telephoto mode) creates a narrow field of view, and therefore requires more images (about 24 at max telephoto setting), but ensures that the joins between each image become almost invisible.
  • Tripod Mount - Maintaining a steady camera position is essential to avoid the image jumping up or down from frame to frame. The E-900 has a tripod mount which allows the camera to be accurately levelled and rotated.
  • White Balance -  Many VR images such as interiors and objects cannot be made with flash as the illumination is too uneven. It is therefore important that the camera can cope with a wide range of ambient lightning.. The E-900 has settings for incandescent, flourescent, sunny and cloudy lightning conditions.
  • Fisheye adapter - Some VR images can be created using two complete 180º images to form a visual spheroid inside which the viewer can pivot horzontally and vertically with complete freedom. These images are created with software called IPIX™ and can simply generated using the E-900 with its' Fisheye Lens adapter. (see http://www.ipix.com)
  • Variable image size - most VR images need to be fairly small (320 x 240 for example) to ensure rapid movement. The E-900's VGA setting allows a reduced resolution image to be taken which ensures faster image creation. However the full resolution setting is ideal for creation of IPIX images with theFisheye adapter as in this case only two shots are needed for a complete 360º spherical image.

Here are some useful hints and tips for the creation of panoramic and Object VR images.

Panoramas

  • Always use a tripod, making sure that it has an indicator dial or scale to show the amount of rotation. Better still, use a purpose-designed rotating device which has calibrated steps to ensure accurate positioning. Manufacturers of these devices include Kaidan (see http://www.kaidan.com)
  • Ensure that the camera mounting is level, so that as the camera is rotated, the field of view does not rise and fall. A tripod fitted with a spirit level is useful to ensure accurate setting.
  • Choose your zoom setting carefully. A wideangle uses fewer images, but will make image joins difficult at the top and bottom of each picture as vertical lines become curved in opposite directions. A zoomed-in (telephoto) setting reduces geometric distortion but requires more exposures.
  • If taking pictures inside, turn off the flash and set the White Balance (in the Manual Rec mode menu) according to the lighting conditions.
  • Try to position the camera so that it rotates about the "Nodal Point" to reduce parallax errors.
    This is the point at which the image may be said to exist inside the camera and reduces image degradation at the overlap areas of adjacent pictures. A special rotator or tripod adapter may be necessary.
  • Be prepared to crop the images after shooting to make the overlay areas as small as possible.
  • Try to take outdoor panorama shots with the sun relatively high in the sky (or even on cloudy days) to avoid extreme ranges of brightness as the camera is rotated.

Objects

  • Use a table-top rotating device such as a turntable. The device should have a click-stop or marker to allow accurate positioning of each frame.
  • Suspend a marker such as a needle on the end of a thread exactly above the axis of rotation of the turntable so as to position the object. This ensures that the object is spun about itself and does not swing around as it is rotated.
  • Set your lighting carefully to ensure that the background does not alter from image to image.
  • Set the camera on a tripod to ensure that the point of view remains totally fixed. Failure to do this will result in the onject appearing to move up and down as it is rotated by the viewer.
  • If the object has an important face or surface, take the first picture with the the object side-on or even facing away. This will ensure that the pictures taken either side of the main point-of-interest match closely.

General

  • Set exposure to Auto Exposure lock (in the Manual Rec mode menu) and take the first picture with the camera at 90º from the main light source to obtain a mid-level setting.
  • Set the image resolution appropriately. Most VR images are fairly small, as this allows the fast flicker-free movement on screen. Unless particulary high resolution is needed (for example with IPIX fisheye images) set the camera to VGA mode for smooth rotation..
  • Take your time with exposure, object positioning, camera tripod levelling etc to obtain the highest quality images. As a VR image is made up of a sequence of individual pictures, just one poor picture will spoil the entire effect.

To view some experimental ad-hoc sample images taken with the E-900, click below:

marshall4.mov (quicktime object movie of miniature guitar amp)
paris320x480.mov (quicktime movie panorama, Paris scene)

Both images were generated with software from PictureWorks™.