For school & volume photographers · Mac
Ruler crops a whole picture day from the geometry of each child's face — eyes to chin — so a bow, big hair or a lean never changes how big the face comes out. Every portrait framed the same way, on your own Mac.
The principle
Every automatic cropper that sizes from the head or the whole person makes the same mistakes: a giant bow, big curly hair, a turned shoulder, a lean — each one changes how big the child ends up. Ruler measures one thing that never changes with any of them.
faceUnit = distance(eye midpoint, chin) crop height = faceUnit ÷ 0.2148 ← the ruler crop top = top of the hair − 5.7% ← headroom crop x = the face, centered
Measured on 130 professionally cropped yearbook headshots, then tuned against 879 of a photographer's own corrections.
A picture day, start to finish
Ruler is not a photo editor — it never touches exposure, color or skin. It has one job, and it does it while you make coffee.
It asks one question — does this shoot deliberately show feet? — so a frame that happened to catch a pair of shoes can't become the only full-length picture in the class.
About thirty photos a second. Every face found, every crop solved, every frame sorted into a crop type and badged on the grid.
Only the exceptions, each with a reason in plain words. Arrows nudge, + − zoom, , . turn the crop, Return approves. Most days it's a handful.
2400 × 3000 at 300 ppi into a new folder, crop type stamped as a star rating so it survives into Evoto. Originals are never written to. A CSV lists every photo and why anything was skipped.
Four crop types
Each type has its own rule for where the frame sits, and each stamps its own star rating into the exported file so the pose is filterable downstream.
Chosen per photo, first match wins: horizontal frame → Top · five stars → Head · the unrated retake of a five-star frame → Head · feet in the frame → Full · everything else → 3/4. Rules are editable per job, and a pose you teach it gets a rule of its own.
The hard ones
Every nudge, zoom and turn from two picture days — 879 of them — was replayed against the engine, and the engine changed wherever the photographer disagreed with it. This is what came out.
A tilted head is leveled by at most 3°. Fully leveling a 10° tilt makes the shoulders look crooked instead — the photographer was turning those back by hand every time.
A crop that would run a little off one side slides back in instead of filling a strip with copied backdrop — while the hair keeps its clearance from the new edge.
A child turned to camera has their face midline off to one side of their own head. Ruler centers a quarter of the way toward the head outline — exactly where 447 hand-checked headshots agreed.
Two photographers shoot two children at the same moment. Ruler tells the cameras apart, so one child never inherits the other's face size.
A giant pencil keeps its eraser and its tip; a letter board keeps its letters. The crop grows around the face until the prop fits, and tells you by how much.
You star one take per child and move on. The unrated take seconds later with the same-sized face is the same headshot, and gets the same crop without a click.
Teach it a pose
Children holding a giant pencil overhead. A letter board. Whatever this school year brings. Tick a handful of frames that show it, name it, choose the crop it should get.
Fits the workflow you already have
Ruler sits in the middle of the day you already run: it takes the frames off your card the way Lightroom left them, and hands Evoto a folder where every crop is level, every face is the same size and every pose is labeled.
Ratings and color labels are read straight from the file's XMP. Five stars means headshot; nothing to re-tag.
Each export carries its type as a star rating — headshot 5, landscape 4, three-quarter 3, standing 2 — so you can filter in Evoto or Lightroom for background work.
Every crop comes out level, every face the same size, and the floor line is kept where it fell. Evoto's background swaps and reflection floors then land the same way on every child in the class instead of wanting a nudge per file.
Standing crops are sized head to feet, so tall and small children fill the frame alike — and the feet and floor stay in the frame, which is exactly what a reflection floor needs.
2400 × 3000 at 300 ppi with metadata and color profile preserved — 4×6, 5×7 and 8×10 without a second thought. Set your own size if you need one.
Extend a seamless backdrop past the frame, or drop the child onto your own plate — the floor line found for you.
The export CSV lists every photo, its crop type, confidence and reasons, and which ones you touched by hand.
Faces are found with Apple's on-device vision. No account, no upload, no children's photographs on anyone's server.
Get Ruler
Download it and run a real picture day — every feature works for three days, no card, no account. When you're sure, a yearly license covers one photographer on two Macs; the key arrives with your receipt and goes in under Ruler ▸ License.
$199 covers Ruler on the Mac. The ClassPhoto Suite is a separate key at its own price.
Signed with a Developer ID and notarized by Apple · macOS 14 Sonoma or newer · Apple silicon and Intel · reads JPEGs
unzip in a terminal — that breaks the app's signature and it will refuse to open.Ruler.app.After the crops
Five browser tools from the same studio, each one turning an export you already have — a GotPhoto zip, a PSPA Index.txt, a roster — into one of the things a school asks for after picture day. They run in the browser on a Mac, a PC or a Chromebook, and no photograph or roster is uploaded.
Ruler is not part of that key. It is a Mac app with its own license, and the two are bought separately: a Suite key does not open Ruler, and Ruler's key does not open the Suite. Your crops feed all five either way — Ruler writes each one to the same path under a new folder, so a folder per class is still a folder per class, which is the shape these tools read a whole school from.
Questions
$199 a year for one photographer on up to two Macs, through Lemon Squeezy. That is Ruler on its own. The ClassPhoto Suite is a separate key at its own yearly price, and neither one opens the other. The first three days after you open the app are free with every feature working. After that the photos still crop and review, but Export asks for a license key — the one in your receipt. "Deactivate on this Mac" frees a seat so the key can move to another Mac, and if the subscription ever lapses, Export closes again; nothing else changes and nothing is lost.
No. Ruler never touches pixels except to crop, resize and — if you ask — fill or replace the backdrop. Do your editing before or after, wherever you do it now.
It still sorts. On a folder with no stars anywhere, a headshot is simply the frame shot closer, and that rule finds them — verified by stripping the ratings from 120 real frames and getting the identical crop type on all 120. Where stars are in use, an unrated frame that isn't a retake is deliberately not a headshot.
Anything Ruler is not sure about: more than one face, a hair outline it couldn't read, a crop that would run off the photograph where the child is cut off, a prop too big to keep whole. Each comes with a reason. On the last 497-photo day, nine.
Never. Exports go to a separate folder, and Ruler refuses an export folder inside the source folder.
Yes — nudge, zoom and turn any crop with the keyboard, and approve it. Your correction is kept with the job, and the next version of Ruler is measured against exactly those corrections.
Mac only. It is built on Apple's on-device face and person detection, which is also why nothing is uploaded.
No. Activating sends the key and this Mac's name to Lemon Squeezy, and the app asks it again when it launches online. Offline, a recently confirmed key keeps working for two weeks. Photographs never leave your Mac.