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A capture target is a chart of known colour, tone, resolution and scale that you photograph in your own setup to produce objective reference data. Use it to build or apply a colour profile, set a neutral white balance, prove you hit a standard via ΔE and MTF, and record true physical size. Shoot a target frame once per stable setup — not in every image — and apply its correction across the whole batch.
Why bother with targets at all?
Without a target, your colour and size claims are guesswork. With one, every capture becomes measurable: you can state the colour error in ΔE, the real resolving power in line-pairs per millimetre, and the true dimensions of the object. Targets are what turn "this looks about right" into a defensible, FADGI- or Metamorfoze-compatible record.
Which targets do I actually need?
| Target | Measures | When to use |
|---|---|---|
| X-Rite ColorChecker (24/SG) | Colour & tone patches | General reflective capture |
| IT8.7 (Kodak/Wolf Faust) | Colour for film | Transmissive originals, slides, negatives |
| Golden Thread / device-level | Full FADGI metric set | Conformance reporting |
| USAF 1951 / slanted edge | Resolution, MTF | Verifying resolving power |
| Scale bar / ruler | Physical dimensions | Any object where size matters |
| Grey card / neutral patch | White balance | Setting neutral exposure |
Most heritage labs keep a ColorChecker plus a scale bar always, and an objective target for conformance days.
How do I position the target correctly?
Placement errors are the commonest mistake. The target must experience the same conditions as the object:
- Lay it in the same plane and at the same distance as the original.
- Light it with the same lamps, angle and intensity — no shadow across the chart.
- Keep it flat and clean; a curled or scuffed chart gives wrong readings.
- Avoid glare on glossy patches by checking at the chosen aperture and polarisation.
A target shot at a different distance or under different light than your objects is worse than useless — it produces a confidently wrong correction.
How do I use the chart to correct colour, step by step?
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1. Place the chart in the capture plane; shoot one raw frame.
2. Open it in your raw tool (Capture One, Lightroom) or a profiler.
3. Set custom white balance by clicking the neutral grey patch.
4. Measure the colour patches against the chart's reference (.cie) values.
5. Build an input profile or apply a correction to minimise dE2000.
6. Apply that white balance + profile to every capture in the batch.For an automated, repeatable route, the open-source Argyll CMS reads the chart and builds an ICC input profile:
bash
scanin target_frame.tiff ColorChecker.cht ColorChecker.cie
colprof -v -qm -D "Bay2_2024-12_StrobeKit" target_frame
# -> target_frame.icc, ready to assign then convert to your working spaceHow do I verify resolution with a target?
Include a resolution target and analyse it rather than trusting the header. A slanted-edge patch fed to Imatest, MTF Mapper or the DCEval tooling returns MTF50 and limiting resolution. If you specified 6 lp/mm of detail but the target resolves only 4 lp/mm, your real resolution is below spec — fix focus, aperture or distance before continuing the batch.
How do I record true physical size?
Put a scale bar (a millimetre ruler or a calibrated photographic scale) in the frame and the file metadata. Later, anyone can derive exact dimensions even if the image is cropped or resized. For 3D or photogrammetry work this scale reference is essential to produce metrically correct models.
What are the common pitfalls?
- Reusing an old target frame after changing lights — re-shoot whenever the setup changes.
- Mismatched plane/distance between chart and object.
- Glare or fingerprints on patches skewing measurements.
- Faded charts — colour targets drift over years; replace per the maker's guidance.
- Assigning vs converting confusion — assign the built profile to interpret, then convert to the working space.
How do I document it?
Log the target type and serial/batch, the session date, lighting, the resulting profile name and the measured ΔE/MTF. This paradata travels with the masters and lets future curators reproduce or audit your colour and resolution.
Key Takeaways
- A target gives objective colour, tone, resolution and size reference data for every batch.
- Keep a ColorChecker + scale bar as standard; add IT8.7 for film and a device-level target for conformance.
- Shoot a target frame once per stable setup, in the same plane, distance and light as the objects.
- Use the neutral patch for white balance, the colour patches to build a profile and minimise ΔE2000.
- Verify real resolution with a slanted-edge/USAF target and MTF, not the nominal ppi.
- Avoid the classic errors: stale target frames, mismatched conditions, glare and faded charts.
- Record target, profile, ΔE and MTF as paradata alongside the masters.
Frequently Asked Questions
What is a capture target and why include one?
A capture target is a manufactured chart with patches of known colour, tone, resolution and scale. Photographing it in your setup gives objective reference data to build profiles, measure accuracy and prove the capture met a standard.
Which colour chart should I use for archival imaging?
An X-Rite ColorChecker (24 or larger) for general reflective work, an IT8.7 target for film and transmissive originals, and an objective device-level target (such as a Golden Thread) when you need FADGI or Metamorfoze conformance figures.
Do I shoot the target in every photo?
No. Shoot a target frame at the start of each session and whenever the setup changes (lighting, lens, aperture, distance). One reference capture per stable setup is enough; you apply its correction to all images in that batch.
How do I use the target to correct colour?
Photograph the chart, then in raw software or a profiling tool measure the patches and build or apply a correction so measured values match the chart's reference values, minimising ΔE. You can also set a custom white balance from the neutral grey patch.
What is a scale bar or resolution target for?
A scale bar records true physical size so dimensions can be reconstructed, and a resolution target (USAF 1951 or a slanted edge) lets you measure actual resolving power (MTF) rather than trusting the nominal ppi.