CFP Advanced Techniques & Methods 3 — Questions and Answers
Question 1: What is the primary purpose of using a gray card when setting white balance in forensic photography?
- To measure the distance to the subject
- To ensure accurate color reproduction under varying lighting conditions (Correct answer)
- To calibrate the camera's autofocus system
- To determine the correct ISO setting
Correct answer: To ensure accurate color reproduction under varying lighting conditions
A gray card provides a neutral reference that ensures the camera renders colors accurately regardless of the ambient light source, which is critical for evidentiary color fidelity.
Question 2: A forensic photographer is tasked with capturing latent fingerprints dusted with white powder on a dark surface. The optimal background for comparison photography would be:
- A white background to create maximum contrast
- A black background to maximize contrast with the white powder (Correct answer)
- A gray background for neutral representation
- No background — photograph in situ only
Correct answer: A black background to maximize contrast with the white powder
A black background provides maximum contrast against white fingerprint powder, making ridge detail clearly visible for examination and comparison.
Question 3: Which photogrammetry technique allows a forensic photographer to create a measurable 3D reconstruction of a crime scene from photographs?
- HDR bracketing
- Structure from Motion (SfM) (Correct answer)
- Focus stacking
- Time-lapse imaging
Correct answer: Structure from Motion (SfM)
Structure from Motion (SfM) uses overlapping photographs taken from multiple angles to compute a 3D point cloud and measurable model of the scene.
Question 4: When photographing a dark interior crime scene with mixed lighting (daylight from windows and incandescent bulbs), the best approach is:
- Set white balance to auto and shoot JPEG
- Shoot RAW and use custom white balance or correct in post-processing (Correct answer)
- Use only on-camera flash to override ambient light
- Convert to black and white to avoid color cast issues
Correct answer: Shoot RAW and use custom white balance or correct in post-processing
Shooting in RAW format preserves all color data, allowing accurate white balance correction in post-processing to handle multiple conflicting light sources.
Question 5: In close-up forensic photography of tool mark evidence, which lighting technique best reveals surface texture and depth of marks?
- Direct frontal flash lighting
- Oblique or raking light positioned at a low angle to the surface (Correct answer)
- Diffuse overhead studio lighting
- Backlit transillumination
Correct answer: Oblique or raking light positioned at a low angle to the surface
Oblique or raking light placed at a low angle creates shadows within the tool marks, revealing three-dimensional surface texture that is otherwise invisible under direct lighting.
Question 6: When a forensic photographer captures images for use in photogrammetric analysis, the minimum recommended overlap between adjacent photographs is:
- 10–20%
- 30–40%
- 60–80% (Correct answer)
- 95–100%
Correct answer: 60–80%
A 60–80% overlap between frames ensures sufficient common feature points for photogrammetric software to accurately compute spatial measurements and 3D models.
Question 7: Which technique is most effective for photographing a latent fingerprint on a curved glass bottle without distortion?
- Position the camera lens parallel to the tangent of the curved surface at the fingerprint location (Correct answer)
- Use a fisheye lens to capture the full bottle in one shot
- Photograph from a 45-degree angle to reduce glare
- Use a telephoto lens from a distance to flatten perspective
Correct answer: Position the camera lens parallel to the tangent of the curved surface at the fingerprint location
Positioning the camera lens parallel to the tangent of the curved surface at the fingerprint location minimizes perspective distortion and ensures accurate ridge detail reproduction.
CFP Advanced Techniques & Methods 3
What is the primary purpose of using a gray card when setting white balance in forensic photography?