Image capture
This page gives site staff the standardised steps for capturing lesion photographs with calibration markers, so that surface-area and related measurements are accurate, consistent, and comparable across visits for the whole duration of the study. It is intended for the site staff who place the markers and take the photographs.
Follow these steps at every imaging timepoint. If an image is flagged by the application, re-capture it before the subject leaves.
Before you start
- Confirm you have enough undamaged markers: set aside any that are torn, wet, curled, or no longer sticky, and use fresh ones
- Clean and dry the skin around the lesion: so the markers adhere and stay flat
- Use the imaging device assigned for the study: and confirm the lesion area is well lit, with no harsh shadows or glare
Placing the markers
Use five markers where possible, and never fewer than three. More markers give a more reliable measurement, so default to five and drop to the minimum of three only when there is genuinely no room for more.
- Spread the markers across the image, over the skin and never over the lesion, not clustered together, so they sample different parts of the frame and different distances from the camera. The markers do not need to ring the lesion or sit at any set distance from it.
- Place markers on healthy, intact skin, never on the lesion itself.
- Keep the markers flat and avoid placing them where the skin folds or curves sharply, for example directly over a flexure. On high-friction sites such as the axilla or groin, choose the flattest nearby skin. The marker is a rigid, flat plane that must not bend, curl, or wrap to follow the skin's curvature.
Taking the photograph
- Get as close as the framing allows while keeping the whole lesion and every marker inside the image. Closer is better; do not exceed about 30 cm, which is the maximum distance.
- Keep the camera as parallel as possible to the skin surface. Avoid steep, tilted angles, which reduce accuracy.
- Use vertical (portrait) orientation by default. If required, keep the same orientation for the calibration images and for every study image so they stay comparable.
- Make sure all markers and the whole lesion are fully inside the frame, with nothing cut off at the edge.
- Do not place markers on the lesion, on broken or blistered skin, or across areas where the skin folds sharply.
- Zooming is not permitted when taking the photograph, and the photograph must not be cropped or edited after capture.
- If using a smartphone, use the primary (main) camera lens only. Ultra-wide, telephoto, periscope, or any other secondary lens is not permitted.
- Check that the lesion and every marker are in sharp focus and free of shadows, reflections, and glare.
- Keep lighting even across the image. On darker skin tones, take care that the image is not overexposed; on lighter skin, that it is not too bright. The lesion border and the white border of each marker should both be clearly visible.
After capture
- Leave the markers in place until the photographs are captured and successfully uploaded.
- Once upload is confirmed, carefully remove the markers and dispose of them per your site's instructions. Markers are single-use; do not reuse a marker on another subject or visit.
- Replace your working stock when it runs low so you always have undamaged markers available.
Do and do not
Do:
- Use five markers (minimum three), spread across the image on healthy skin.
- Press markers flat, with no wrinkles. The marker is a rigid, flat plane that must not bend, curl, or wrap to follow the skin's curvature.
- Shoot as close as the framing allows, no farther than about 30 cm, with the camera parallel to the skin.
- Shoot in vertical (portrait) orientation by default.
- Keep all markers and the whole lesion in frame, in focus, and evenly lit.
Do not:
- Place markers on the lesion, on broken or blistered skin, or where the skin folds sharply.
- Let markers wrinkle, lift, curl, or sit in shadow or glare.
- Crop a marker or the lesion at the edge of the frame.
- Shoot at a steep angle, or from farther than the maximum distance.
- Reuse markers, or use any that are torn, wet, or no longer sticky.
Placement examples by condition
Each comparison below pairs the same scene shown two ways, using illustrations. The green Correct panel shows the right placement; the terracotta Incorrect panel beside it shows the same site done wrong, with a note explaining why.
Hidradenitis suppurativa
Why this is correct: The markers sit on healthy skin spread around the axilla, each kept clear of the lesion clusters, so the whole area stays visible.
Why this is wrong: A marker is placed on a lesion cluster, hiding tissue the measurement needs and biasing the area.
Why this is correct: The markers are placed on healthy skin around the axillary lesions, so each lesion stays fully visible.
Why this is wrong: Here the markers are placed on top of the lesions, covering the tissue the measurement needs.
Why this is correct: Every marker sits on clear skin between the lesions, spread around the site.
Why this is wrong: Markers placed directly on the nodules hide the lesion and distort the measured area.
Bullous pemphigoid
Why this is correct: Five markers are spread around the affected area, so they frame the whole region being measured.
Why this is wrong: Markers are placed on top of the blisters and eroded areas, hiding the lesions the measurement needs.
Why this is correct: Five markers are spread on intact skin around the blister cluster, each kept clear of the lesions.
Why this is wrong: An extra marker is placed in the middle of the blister field, among the lesions, instead of only on clear skin around them.
Why this is correct: One region is framed at a workable distance with five markers spread around it.
Why this is wrong: Too many lesions are crowded into a single wide frame with markers scattered across all of them; photograph each lesion separately under its own five markers.
Pyoderma gangrenosum
Why this is correct: Five markers are spread around the ulcer, giving the most reliable measurement.
Why this is wrong: Only two markers are used. Place at least three, and ideally five, spread around the lesion.
Why this is correct: The markers sit on healthy skin about 1 cm from the ulcer border, spread around it.
Why this is wrong: The markers ring the ulcer right at its border instead of on healthy skin about 1 cm away, so they touch the lesion edge.
Troubleshooting
Measurements look inconsistent
If lesion measurements appear inconsistent between visits:
- Verify the markers were placed flat on healthy, intact skin and are fully visible in the frame.
- Confirm the photograph is in sharp focus, taken within the maximum distance, with the camera parallel to the skin.
Storage and handling
- Store markers in a cool, dry place to preserve adhesive quality.
- Do not use markers that are expired, torn, or have lost their adhesive backing.
- Keep markers in their original packaging until ready for use.
Managing marker supply
- Ensure each site has an adequate supply of markers before imaging visits begin.
- Monitor inventory regularly and reorder before supply runs low.
- Keep a log of marker usage so you can anticipate reorders and avoid running out before a scheduled imaging visit.
- Contact your designated Legit.Health contact to request additional marker sets.