3D Musketeers // Scanning Series

How accurate is a 3D scan?

The honest answer is "it depends", and this page says on what. Three words that get mixed up, the six things that move the number, the figures the makers publish for the scanners we run, when a scanner beats a probe or a CT machine and when it does not, how we check our own work, and what we will not promise.

Accuracy, precision, resolution

three different questions

Accuracy is how close a measurement lands to the true size. Precision is how tightly repeated measurements group, true or not. Resolution is the smallest feature the scan can still tell apart: the spacing of the points. A scanner can be precise and wrong (a calibration drift), or accurate on average and noisy. A spec sheet usually quotes accuracy and resolution; the deviation report at the end of a job is where you see them meet.

Accuracy Precision Resolution

Accuracy: "Is the hole really 40.0 across?" Quoted in millimeters, as in 0.05 mm.
Precision: "Scan it twice, get the same answer?" Checked by repeating, and by calibration.
Resolution: "Does that thin slot even show up?" The point spacing; finer costs time and file size.

accuracy = close to true precision = repeatable resolution = smallest detail

What moves the number

the same scanner does not give the same result on every object

Size of the object

A coin-sized part gets the fine scanner and the finest detail. A building gets LiDAR, which trades fine detail for range. We pick the scanner that fits the object, not the other way round.

The surface

Very shiny, black or see-through surfaces are harder for any optical scanner. Tell us the material up front and we plan for it, usually a matte spray, before the scan rather than after.

Coverage

A face the light never reached is a hole, not a measurement. Undercuts, deep pockets and the underside need their own passes or a second orientation.

The tool

Handheld structured light, a locked turntable, blue laser, LiDAR, photogrammetry and CT all see differently. How each one works, with pros and cons.

Calibration

A scanner only holds its figure if it is kept calibrated. We keep our scanners certified and can provide calibration paperwork on request.

What happens after

The scanner's figure is not the figure of a part printed from it. Printing and machining add their own tolerances. Ask about both when a fit matters.

The scanners we run

manufacturer-stated figures, as published on this site

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Scanner	Method	Stated figure	Object size	Color	We reach for it when
Artec Spider	Handheld structured light	Detail down to 0.05 mm (50 microns)	Small, intricate parts	Yes	Threads, fillets, tight tolerances, small ornaments
Artec Eva	Handheld structured light	Up to 0.1 mm accuracy	Medium parts	Yes	Reverse engineering and inspection; our workhorse
Artec Leo	Handheld structured light, no PC	Around 0.1 mm	Medium to large, on site	Yes	Bolted to a machine, tight space, at your site
Artec Ray	LiDAR, tripod	Range 300+ ft; coarser fine detail	Room to stadium	Camera overlay	Buildings, bridges, scenes, vehicles in context
Matter and Form THREE	Turntable structured light	Highest desk-scale detail of our set	Fits the table	Yes	Desk-sized parts that have to be exact and repeatable
Creality blue laser	Blue laser + IR handheld	Good on shiny metal	Part to vehicle	Varies by model	Machined and cast metal, dark or glossy things
Industrial CT	X-ray, through partner Lumafield	Sees inside the part	Small to medium	No	Internal features, porosity, sealed assemblies

These are the makers' stated values for the instrument. They are not a guarantee for every part: the surface, the size and the coverage decide what a given scan reaches. Where it matters, ask for the deviation report, which shows the result on your part rather than a number from a brochure.

Scanner vs CMM vs CT

when a scan is the right tool, and when it is not

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Method	What it measures	Touches the part	Speed	Inside the part	Best at	At 3D Musketeers
Optical 3D scanner	The whole visible surface, millions of points	No	Fast	No	Free-form shapes, whole-part comparison, color, fragile or evidentiary objects	In our shop
CMM (touch probe)	Individual points and features, one at a time	Yes	Slow	No	A few critical dimensions to a certified tolerance on a rigid part	We do not run one; we will say so if your job needs it
Industrial CT	The full volume, outside and inside	No	Slow	Yes	Internal channels, voids, sealed assemblies, porosity	Through our partner Lumafield

A scanner answers "what is the whole shape, and where does it differ from the model". A probe answers "is this one bore exactly 40.00". A CT machine answers "what does it look like inside". Line of sight is the scanner's limit: if the light cannot see it, it is not measured.

How we check our work

what stands behind a file we hand you

Validation against the scan

Before a reverse-engineered model ships, we compare it back to the original scan data and produce a color-mapped deviation report. On real jobs the agreement is often within a few hundredths of a millimeter. Where it drifts, we fix the model and compare again. See the stage.

Calibration

We keep our scanners certified and can provide calibration paperwork on request. We scan with the Artec Spider, Eva, Leo and Ray.

No contact, no marker dots

Our structured-light scanners do not touch the object and do not need marker dots on most parts. For fragile, historic or evidentiary objects that is the whole point.

For legal and forensic work

If a case needs it, our team will testify on request about how a scan was made: how it was captured and handled, not opinions on the case. Raise it up front so we can plan and quote it. Legal and insurance scanning.

What we do not promise

said plainly, so there are no surprises

A tolerance before we see the part

The surface, size and coverage decide what a scan reaches. We quote the approach first and show the result in the report.

The inside of a sealed part

Optical scanners measure what light can reach. For internal features we go to CT through our partner Lumafield.

Probe-level certified points

We do not run a CMM. If your job is a handful of critical dimensions to a certified tolerance, we will tell you straight and point you to the right tool.

That a printed copy equals the scan

Printing adds its own tolerance on top of the scan's. When a fit matters, we talk about both before the job.

Analysis or admissibility

We deliver accurate 3D data. For legal, forensic and engineering work the analysis and conclusions stay with your expert. The court decides what is admitted. We are not lawyers and this is not legal advice.

A number we did not measure

The figures above are the makers' stated values. We label them that way on purpose.

Questions

short answers

How accurate are your scans?

It depends on the scanner we use. Our Artec Spider captures detail down to 50 microns (0.05 mm) for small parts, the Eva offers up to 0.1 mm accuracy for medium-sized objects, while the Leo and Ray trade some of that precision for portability and long range. Those are the makers' stated figures for the instrument; the deviation report shows the result on your part.

Can you scan something shiny, dark, or transparent?

Those surfaces are harder for any optical scanner, so tell us the material up front and we plan for it before the scan, not after. Our scanners do not need marker dots, and we do not touch the object.

Can you provide calibration paperwork?

We keep our scanners certified and can provide calibration paperwork on request. The court decides what is admitted, and we cannot promise a scan will be. We are not lawyers and this is not legal advice.

Is a 3D scanner as accurate as a CMM?

They answer different questions. A probe measures a few points to a certified tolerance; a scanner measures the whole surface, millions of points, without touching it. We do not run a CMM. If your job needs one, we will say so.

Will a part printed from the scan match the original?

Closely, but printing adds its own tolerance on top of the scan's. When a fit matters, tell us and we plan both steps together. 3D printing.

How a scan becomes CAD · What you get back · Types of 3D scanners · 3D scanning services · Tell us about your object.