Before and Afters – Case Study
Background

Before and afters are important part of patient documentation, documenting a patient photographically is the only true testament to a practitioner’s work. Doing this accurately can prove challenging. The distance of the light source to the patient, distance of the patient to the camera, angles, and camera exposure, all need to be the same between sessions in order for your images to look identical. Distances and angles can be standardised, but how do we keep the camera exposure the same between sessions when using smart devices which don’t have manual settings? This case study looks at whether the Clinical PhotoPro System is able to stabilise the auto settings on a mobile phone/tablet camera.

 

Photography basics 

Shutter-speed relates to the speed at which the shutter on a camera operates and the speed at which it lets light onto the sensor. The faster the shutter-speed the less light falls on the sensor, and the slower the shutter-speed the more light is allowed to fall on the sensor. When a camera is in auto, the available amount of light will determine the speed of the shutter. If there is not sufficient light available the camera will lower the shutter-speed. It is important to note that if the shutter-speed is too slow, the image will lend itself to being blurred. 

 

ISO refers to the sensitivity of the digital camera’s sensor. The more sensitive the sensor is, the more noise the image will have. This is a type of visual distortion that appears as random specks on the images [1].  The higher the ISO number, the more noisy the image will be, resulting in reduced quality. If there is insufficient light on your subject, the camera will increase the ISO to correctly expose the subject.

 

Aperture is responsible for depth of field, or which part of the image is in focus [2]. It is important to note that the aperture on current smart devices are fixed

 

Method

For the case study, a subject was photographed on 4 different days to simulate a patient revisiting a clinic. The Clinical PhotoPro system’s positioning markers were used to standardise distances and angles. The system’s stable lighting environment overrides the camera’s auto settings. An iPhone Xs was used. All images were taken handheld.

 

Data captured

The image’s metadata was captured to verify:

  • The date and time the image was taken

  • The camera used

  • The shutter-speed the camera used

  • The ISO the camera used

  • The aperture (fixed on the test camera)

 

Baseline analysis

In order to capture data of what camera settings would be used in poor lighting conditions, a photograph was taken with standard overhead LED downlights. The Clinical PhotoPro System was then used to capture 4 images to see how consistent the shutter-speed and ISO would be.

 

 
Screenshot 2021-09-21 at 17.17.12.png
Image 1. Clinical PhotoPro off 
Results

With the Clinical PhotoPro System off, and using standard overhead LED downlights, the camera reduced the shutter-speed to 1/20th sec. There is a high chance the image will blur at this low speed. The ISO was increased to 640, on closer observation, visual distortion is visible. This image is of poor quality.

 

With the Clinical PhotoPro System on, the camera’s shutter-speed was increased to 1/120th sec. The ISO was lowered to 100, producing a high-quality image. The patient was photographed over 4 days with the patient having to be repositioned and the camera had to readjust to the lighting for each session.

 

 
Screenshot 2021-09-21 at 16.16.17.png
Image 2. Metadata with Clinical PhotoPro on
Conclusion:

The Clinical PhotoPro System was able to successfully stabilise the shutter-speed to 1/120th sec with zero variance. A shutter-speed of 1/120th will ensure pin-sharp images of a stationary subject while the camera is handheld. The ISO was stable at 100, also with zero variance. The system was also able to keep the white balance consistent, ensuring accurate and realistic skin tones.

 

 

 
IMG_8785 Clinical PhotoPro.jpg
Image 3. Results - 4 images over 4 days
References:

1: Cambridgeincolour.com. 2021. Digital Camera Image Noise: Concept and Types. [online] Available at: <https://www.cambridgeincolour.com/tutorials/image-noise.htm> [Accessed 22 August 2021].

 

2: Nave, R., 2021. Stops, Pupils, and Apertures. [online] Hyperphysics.phy-astr.gsu.edu. Available at: <http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/stop.html> [Accessed 20 July 2021].