How to photograph a coin
NumiAssist never takes the shot for you – the shutter is always yours. This guide covers the things that actually change the result: the surface, the light, the distance, the angle, and the one view that needs several frames.
Start with the surface and the light
Put the coin on a light, contrasty surface – a sheet of white paper is enough. The app separates the coin from whatever lies behind it, and a plain, even background makes that separation exact.
Light matters more than the phone does. A window or a lamp to the side rakes across the relief and reveals it. Light coming from directly behind the phone flattens the coin and drops your own shadow onto it.
- The torch is for worn metal. In the Regular mode it is on by default: circulated, worn and toned coins gain contrast from it.
- Shine hates the torch. For proof, mint luster and coins in capsules the torch defaults to off – a side lamp gives you the same detail without a mirror-white spot.
- The mode is chosen once per lot. Regular, Brilliant or Capsule is picked on the lot screen and holds for every shot in it, so both sides come out looking like each other.
The relief casts small shadows – that is what makes it readable.
Flat, shadowless – and the phone shades the coin it is photographing.
Come close, and let the viewfinder be the shot
What you see on screen is exactly what the photo keeps. Zoom is your framing, not a magnifier applied afterwards: later, in the editor, the crop can be adjusted inside that frame – but never beyond what you saw here.
- Fill the frame with the coin. More coin pixels means more real detail. On iPhones with a macro lens the app switches to it visibly once the main camera can no longer focus that close – and you can switch that off.
- The shutter is always available. The on-screen button, either volume key, or a 0, 2 or 5-second timer when pressing the phone is what shakes it.
- Anything that holds the phone beats a steady hand. A stack of books, a kitchen shelf, a tripod – all of them out-shoot the best grip, and the timer removes the last shake.
The coin does not have to lie flat
A coin on the table and a coin standing in a holder are both perfectly normal starting points. The phone does not have to be parallel to it, and there is no angle you must reach before the shutter unlocks – it never locks.
The app outlines the coin as an ellipse. An ellipse is what a circle looks like from an angle, so the outline follows the coin whether you shoot straight down or well off to the side, and the crop follows the outline.
What the app will not do is straighten the perspective. Squeezing an angled coin back into a circle stretches the relief and shifts the legends – that is a distortion, not a correction. The photo keeps the geometry you actually shot.
The classic case: the outline comes out almost round.
Equally valid: the outline becomes an ellipse, and the crop follows it.
Make the second side match the first
A lot reads as one object when both sides share an angle and a light. Three instruments exist for exactly that, and all three are visible on the capture screen.
The tilt meter
The first shot of a lot becomes the target. The meter then shows your current tilt and roll against it and quietly says “matched” when you are there. Double-tap it to forget the target and set a new one.
Light
Freezes exposure and brightness for the whole lot, so the second side is not metered brighter than the first and the two photos do not need rescuing afterwards.
Ghost
Lays the previous shot faintly over the viewfinder. Line the coin up with the ghost and the two frames sit the same way, at the same size.
Glare: move the light, not the coin
Any shiny coin glares – that is optics, not silver. The viewfinder marks blown highlights with zebra stripes: wherever the stripes crawl, the detail is already gone, and no amount of processing brings it back.
- Lower the lamp first. A shallower angle across the coin turns a mirror spot back into relief. Moving the light beats every setting.
- Then turn the torch off. It sits right next to the lens, so on a shiny surface it reflects straight back. A window does not.
- Then lower Brightness until the stripes disappear. A slightly dark frame keeps its detail; a blown one has none to keep.
- Background blur is not a glare tool. It softens what lies behind the coin – a busy tablecloth, a shadow line – and never touches the coin itself.
The edge, one segment at a time
The edge is the only view built from several frames: a rim is longer than any single shot can hold sharply. This is the one deliberate exception to “one view, one shot”.
- Frame a stretch. Point at one part of the rim and set the rectangle so it holds that stretch and little else.
- One press, one segment. The rectangle is remembered as that segment's crop, so segments come out the same height.
- Turn the coin, shoot again. Four to six segments usually cover a full circumference with a little overlap.
- Finish, then stitch. “Finish shooting” opens the segment editor. Drop or re-shoot anything soft, and only then stitch them into one strip – the stitch never happens behind your back.
Turn the coin, not yourself: the light stays where it is, so every segment is lit the same way.
What the processing does – and what it refuses to do
Knowing where the line is saves you from fighting the app: everything on the left it handles for you, and nothing on the right will ever happen behind your back.
It does
- Finds the coin and crops to it, with the margin you set
- Evens out the background so the listing looks tidy
- Tames glare that still has detail underneath
- Keeps colour true to the metal, whatever the metal is
- Preserves the full original frame – every edit stays reversible
It doesn't
- Paint in detail that was never captured
- Straighten perspective, because that deforms the coin
- Hide scratches, spots, cleaning marks or wear
- Grade the coin, judge authenticity or suggest a price
- Put a watermark on the images you export
The thirty-second checklist
- A plain, light surface, and the coin free of dust – a fingerprint on the field shows up more than you expect.
- Light coming from the side, and the phone's own shadow off the coin.
- The coin filling the frame, and focus confirmed before you press.
- The mode chosen for the lot, with the torch matching it – on for worn metal, off for shine.
- No zebra stripes on the relief you care about.
- The second side at the same angle – the meter says matched.
Everything here is a suggestion, not a gate. The manual shutter always works, whatever the instruments think of your lighting.
Try it on the coin in front of you.
Seven days, every feature, no card tricks. The first lot takes minutes.
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