Skip to content

Photography

Photographs are the raw input for reconstruction. Their geometric diversity determines reconstruction quality.

HemoVision requires two types of images:

  • Overview images
  • Detail images

Overview Images

Overview images are used to reconstruct the 3D geometry of the scene.

They must:

  • Show as many markers as possible, though it is not required that all markers are visible in all images
  • Overlap significantly with each other
  • Be taken from different viewpoints, so make sure to move around

As a rule of thumb:

  • Take at least 20 overview photographs
  • Ensure each detail marker appears in at least 5 overview images with sufficient context

Because photographs can be taken freehand without any constraints, taking 20+ photographs takes just a few minutes. We always recommend to take some extra photographs. You can always use less in your analysis.

Tip

Walk around the documented region in a semi-circle. Take sidesteps. Vary the height of you camera. Small variations in camera position (left, right, up, down) allow you take multiple photographs from the same position.

Warning

Rotating in place is not good documentation practice. Avoid standing in one position. Move around the scene to vary camera viewpoints.

Below are some examples of good overview photographs. The screenshot after shows the reconstructed scene, as well as the camera positions for all overview images (in blue). Notice how the photographer walked around the scene in a semi-circle, also varying the height at which photographs were taken.

Reconstruction in HemoVision, with the blue frustums indicating camera positions of the overivew images.

Detail Images

Detail images are close-ups used for stain analysis and pattern classification.

Each detail image:

  • Contains (at least) one detail marker
  • Covers a planar region typically between 30–70 cm wide
  • Does not need to be taken parallel to the surface; perspective distortions are corrected automatically

Multiple detail photographs may be taken from the same marker, covering overlapping or adjacent regions.

Warning

A detail image typically contains a single detail marker. If multiple detail markers appear in a detail image, they must lie on the same plane.

Below are some examples of good detail photographs.

Summary

Below is a summary and some considerations to take into account when documenting a scene for HemoVision.

Info

  • Use a camera with at least 10 megapixels.
  • Avoid wide-angle or fish-eye lenses, as they distort the image.
  • Use diffuse lighting or bounce flash to minimize glare.
  • Ensure sharp focus. Motion blur and poor lighting reduce marker detection reliability.
  • Take a minimum of 20 overview images, and at least one photograph of each detail marker.
  • You cannot take too many photographs, you can take too few.

Found a mistake?

Did you find a mistake, or does a page contain outdated information or something that is not working correctly? Please let us know so we can review it and fix it as soon as possible.

Forentrics - Bringing Evidence into Focus