Disclaimer:
As a condition to the use of this document and the information contained therein, the SWGDE requests notification by e-mail before or contemporaneous to the introduction of this document, or any portion thereof, as a marked exhibit offered for or moved into evidence in any judicial, administrative, legislative or adjudicatory hearing or other proceeding (including discovery proceedings) in the United States or any Foreign country. Such notification shall include: 1) the formal name of the proceeding, including docket number or similar identifier; 2) the name and location of the body conducting the hearing or proceeding; 3) subsequent to the use of this document in a formal proceeding please notify SWGDE as to its use and outcome; 4) the name, mailing address (if available) and contact information of the party offering or moving the document into evidence. Notifications should be sent to secretary@swgde.org.
It is the reader’s responsibility to ensure they have the most current version of this document. It is recommended that previous versions be archived.
Redistribution Policy:
SWGDE grants permission for redistribution and use of all publicly posted documents created by SWGDE, provided that the following conditions are met:
- Redistribution of documents or parts of documents must retain the SWGDE cover page containing the disclaimer.
- Neither the name of SWGDE nor the names of contributors may be used to endorse or promote products derived from its documents.
- Any reference or quote from a SWGDE document must include the version number (or create date) of the document and mention if the document is in a draft status.
Requests for Modification:
SWGDE encourages stakeholder participation in the preparation of documents. Suggestions for modifications are welcome and must be forwarded to the Secretary in writing at secretary@swgde.org. The following information is required as a part of the response:
- Submitter’s name
- Affiliation (agency/organization)
- Address
- Telephone number and email address
- Document title and version number
- Change from (note document section number)
- Change to (provide suggested text where appropriate; comments not including suggested text will not be considered)
- Basis for change
Intellectual Property:
Unauthorized use of the SWGDE logo or documents without written permission from SWGDE is a violation of our intellectual property rights.
Individuals may not misstate or over represent duties and responsibilities of SWGDE work. This includes claiming oneself as a contributing member without actively participating in SWGDE meetings; claiming oneself as an officer of SWGDE without serving as such; claiming sole authorship of a document; use the SWGDE logo on any material or curriculum vitae.
Any mention of specific products within SWGDE documents is for informational purposes only; it does not imply a recommendation or endorsement by SWGDE.
1. Purpose
The purpose of this document is to provide an understanding of how reflected ultraviolet radiation (UV) photography can be used to document and examine evidence.
2. Scope
This document will provide a basic understanding of the principles of reflected UV photography, the equipment needed, its use when documenting and examining evidence, and procedures for capturing images. This covers an advanced photography technique and does not address basic principles of photography.
3. Limitations
- CCD and CMOS sensors detection limit and potential sensor damage over time
- Exposure to UV may denature DNA
- Glass lenses may limit UV transmission
- Not all substrates and surface materials are conducive to reflected UV
4. Equipment
Please reference SWGDE Photographic Equipment and Infrastructure Recommendations prior to implementation of new equipment or procedures.
- A full spectrum camera or a camera that has been professionally modified to allow for the capture of images
in the UV spectrum.
- Full spectrum cameras are sensitive to wavelengths of energy from UV, visible, and infrared (IR).
- Lenses that transmit UV radiation.
- UV focuses at a different point than visible light and each lens may have a different focus It is important to test the camera with the lens prior to use. This is especially true when a camera has been professionally modified.
- For comparative analysis photography, a fixed focal length macro lens is recommended.
- For documentation photography, a variable focal length lens may be utilized; however, this may cause or create distortion of the image.
- Filters
- UV transmission filters
- IR blocking filter
- Visible band pass filter (if using a full spectrum camera)
- Light source which emits energy in the UV-A spectrum (315-400nm)
- Typically, UV light sources come in 254nm and 365nm
- Research indicates UV wavelengths <280nm will denature DNA rapidly during exposure.
- Remote shutter release
- Sturdy tripod or copy stand capable of various angles and positions
- Digital storage media
- Standardized scales of various sizes
- Appropriate Personal Protective Equipment (PPE)
5. Basic Principles Behind UV Photography
The visible portion of the electromagnetic spectrum (Figure 1) includes wavelengths of approximately 400-700 nm. UV is outside the visible spectrum of light, approximately 10-400 nm.
UV photography takes advantage of a camera sensor’s ability to capture wavelengths that are outside the visible spectrum. UV reflectance photography is a technique to capture UV energy. Subjects that reflect UV energy will appear lighter in appearance.
This technique is beneficial for visualizing details which are not observable under visible light but react differently to UV energy. Documentation of evidence such as healing injuries and diminished bruising, concealed evidence, latent impressions, surface disturbances and questioned documents may benefit from UV photography.
UV transmission filters are designed to allow UV wavelengths to pass through the camera lens to the sensor while blocking visible light wavelengths; some UV filter also transmit IR; therefore, an additional IR blocking filter may be needed.
Note: Figure 2 demonstrates the transmitted wavelengths of UV radiation and the percentage of IR transmission (IR leakage). To eliminate any interference from IR leakage, an IR blocking filter should be used.
Figure 3. Examples of UV Filters
| Filter | Transmitted wavelengths (nm) | IR leakage |
|---|---|---|
|
Kodak 18A |
300-400 |
14% at 746 nm |
|
B&W 403 |
300-400 |
17% at 746 nm |
|
PECA 900 |
250-400 |
28% at 710 nm |
|
Hoya U330 |
150-400 |
50% at 715 nm |
|
Baader U-Venus |
300-400 |
0.15% at 737 nm
0.3% at 813 nm
0.1% at 872 nm |
|
Kolari Vision UV |
320-400 |
0.025% (unknown) |
|
Schott UG-1 |
300-400 |
9% at 746 nm |
Note: This is not a comprehensive list and the manufacturers listed in the chart should not be construed as an endorsement.
6. Examples of Reflected UV Photography Using a Baader U Filter and 365 nm Light Source
6.1 Bite mark on skin
6.2 Thermal receipt
6.3 Impression on a waxed floor
7. Procedures for Reflected UV Photography
These procedures are written for a full spectrum camera; however, if you are using a UV converted camera, then skip steps 6 – 8. It is suggested that the subject also be documented using visible light photography. If utilizing a preconfigured system, refer to the appropriate user manuals.
- Mount the camera to a tripod, copy stand or another sturdy device
- Set camera to the lowest ISO for the lighting conditions
- Set the camera to manual mode
- Set the camera to the appropriate file format
- Compose the subject so that it is perpendicular to the camera – place a scale and label on the same plane as the subject
- Apply even and direct lighting (do not diffuse) to the subject
- Place a visible bandpass filter on the camera and focus
- Capture image with visible light; review and adjust as necessary
- Place an appropriate UV filter on the camera
- Apply even and direct UV lighting
- Bracket for proper exposure, capture images, review and adjust as necessary
History
| Revision | Issue Date | Section | History |
|---|---|---|---|
|
1.0 DRAFT |
2019-09-19 |
All |
Initial draft created and voted by SWGDE for release as a Draft for Public Comment. |
|
1.0 DRAFT |
2019-09-29 |
— |
Formatting and technical edit performed for release as a Draft for Public Comment. |
|
1.0 |
2020-09-17 |
|
Voted for release as final publication |
Version: 1.0 (September 17, 2020)