What the tool actually does
Three steps, all on one screen.
You frame the slide. The photo you drop usually shows the whole cardboard mount plus the white light around it. The frame on the picture is locked to the slide’s real shape — 3:2, wide or tall — so you drag it over the slide’s window and the cardboard falls outside it. Turn buttons straighten a photo taken sideways, and the mirror tick fixes a picture photographed through the back of the film.
It measures the light inside the frame. One tap — done automatically when the photo loads — reads the brightest and darkest points of the picture inside the frame, separately for red, green and blue, and stretches each color to full range. That removes the dimness and the color cast of photographing a slide on a phone: the white point is sampled inside the frame, so the bright backlight around the mount never pulls the result. The numbers it measured are shown in the line under the picture, and the button switches the fix off again if you want the light exactly as photographed.
You save it. JPG or PNG, at the crop’s own pixels or resized to an exact 4 × 6 inch print file (1200 × 1800 pixels — the classic print size, and the same 3:2 shape as the frame, so nothing is cut off to fit).
Which side faces the camera, and why it matters
Hold the slide up to a lamp: one side shows the picture clearly, the other may show it slightly cloudy or backwards through the film base. The clear side — usually opposite the handwritten label — faces the camera. Photographed from the other side, the picture arrives mirrored, which matters more than it sounds: writing on signs and shirts reads backwards, and a wedding ring changes hands. The mirror tick undoes it. The handwritten label itself is worth keeping: read it and note it before you crop — it is often the only place Great-Aunt’s handwriting records who is in the picture and when.
Why there is no color “before” magic here
This tool deliberately does three things and no more: crop, straighten, correct the light of the capture. It does not repair dust and scratches (the old photo scratch remover does that, after), it does not invent color or sharpness, and it is not AI — every change is a measurement and a stretch, which is the same work a darkroom printer did by hand. That restraint is why it can honestly promise that nothing is uploaded: moving information that is already in your photo needs no server.
From a tray of slides to prints for the album
Convert the slides worth keeping, one photo per slide: lay the slide on a phone or tablet showing a plain white page at full brightness, hold the camera flat and square, no flash. Then check each saved photo against the sizes labs sell with the photo print size checker, fix faded color with the faded photo color restorer, and crop one out of several with the image cropper if you photographed two mounts at once. The whole job — viewing a tray without a projector, what each way costs, and the label habit that keeps the names — is walked step by step in the guide How to view old slides without a projector.
Working from a box of loose strips rather than mounted slides? That is the negative to positive converter — different film, different math, same browser.
Questions
Which side of the slide faces the camera?
The side with the picture you can see — the emulsion side, usually the side the handwritten label is NOT on. Lay the slide on the light with the label facing away from the camera. If the picture comes out back to front, tick 'The picture is mirrored' and it flips back.
Why does my slide photo come out mirrored?
A slide is a piece of film in a cardboard mount, and film has a front and a back. Photographed from the back — which is easy to do, because both sides look similar against the light — the picture arrives left-to-right flipped: writing reads backwards, wedding rings change hands. The mirror tick on this page flips it back in one step.
My slides look faded and orange. Can this fix that?
The light fix here corrects what the camera recorded — a dim or yellowed photo of the slide — by stretching each color back to its full range. It cannot bring back dye the slide itself has lost. If the slide has faded, convert it here first, then run the saved photo through the faded photo color restorer, which measures how far each color drifted and slides it back.
Do slides need inverting, like negatives?
No. A slide is a positive — the picture on the film already looks the right way round, which is why a slide show worked in a projector. Negatives carry an orange mask and need a measured inversion; that is a different job done by the negative to positive converter. A slide only needs the mount cropped off and the light corrected.
How big can I print the result?
The saved photo is never more than 2400 pixels on the long side, and the frame crop makes it smaller still — typically 1300 to 1900 pixels wide from a phone photo. That is a sharp 4 × 6 inch print (which needs 1200 × 1800 pixels) and an honest ceiling of about 20 cm (8 in) wide at 300 DPI. The photo print size checker names the verdict for any file you have saved.
Are my slides uploaded anywhere?
No. The cropping, the light measurement and the download all happen in the page you have open. Nothing is sent to a server, there is no watermark, no daily limit, no account — and no app install.