An important diffraction effect in infrared photography

Area of Science:

• Optical imaging
• Medical photography
• Dermatology

Background:

• Bruising studies utilize infrared imaging for documentation.
• Standard imaging protocols aim for artifact-free recordings.
• Recent photographic equipment may introduce unforeseen variables.

Purpose of the Study:

• To investigate an anomalous circular density observed in infrared images of bruises.
• To identify the source of the observed imaging artifact.
• To characterize the optical properties of the imaging equipment responsible.

Main Methods:

• Observation of a consistent artifact during a study on bruising.
• Analysis of black-and-white infrared photographic records.
• Systematic investigation of photographic lenses used in the study.
• Testing of Micro-Nikkor lenses at various aperture settings.

Main Results:

• A circular area of density was consistently observed in the center of contusions on infrared records.
• This artifact persisted throughout the visible lifespan of the bruise.
• Investigations identified 105 mm f/2.8 Micro-Nikkor lenses as the source.
• Unacceptable diffraction was confirmed at aperture settings smaller than f/11.

Conclusions:

• 105 mm f/2.8 Micro-Nikkor lenses exhibit significant diffraction artifacts at smaller apertures (below f/11).
• This diffraction causes a distinct circular density on infrared imaging of bruises.
• The findings necessitate careful lens selection and aperture control in infrared dermatological imaging.