Scanning, image quality, OCR and safe sharing

Offices, banks, schools and government services often ask for a copy of a document: a certificate, a letter, a form with a signature. A scanner or a phone camera turns the paper into a file you can send. A poor scan can be unreadable or enormous, and a careless one can expose details you meant to hide. This lesson shows how to make a clear scan, how a computer can read the words in it, and how to share the result safely. Use only practice pages in the exercises, never a real identity document.

What a scanner does

A scanner is like a very careful camera. A bright light moves across the page and a sensor records tiny dots of colour. The result is an image, a grid of dots called pixels, not a document with letters. This matters: a scanned page is a picture of text. You cannot select a word in it, search for one, or copy it into an email until a program reads the picture, which is called OCR (see below).

A flatbed scanner has a glass plate where you place one page face down. A sheet-fed scanner or the feeder on a multi-function printer takes a pile of pages. Many printers include a scanner. A phone camera also works well if you hold it straight above the page in good light, and many phones have a scan mode in their camera, notes or files app that straightens and crops the page.

Settings that matter

• {{scan-resolution|Resolution}}, measured in dots per inch (dpi). More dots mean more detail and a bigger file. 150 dpi is enough to read on screen. 300 dpi is the usual choice for text and for OCR. 600 dpi is for small print, photographs you may enlarge or documents you want to keep as a record.
• Colour mode. Colour records everything. Greyscale uses shades of grey and is smaller. Black and white uses only two tones, is smallest and suits plain text, but it can make photographs and stamps look harsh.
• File type. A PDF is best for documents, and can hold many pages in one file. JPEG suits photographs. PNG suits sharp graphics and screenshots. A JPEG compresses with some loss of quality, so avoid saving text pages as low-quality JPEGs.
• Page size and area. Select the correct size, usually A4, so the scan is not cut off or full of empty margin.

OCR: turning a picture of words into real text

OCR (optical character recognition) is software that looks at the picture of a page, recognises the shapes of letters and adds the text back. The result is often a searchable PDF: it looks like the scan, but an invisible layer of real text sits behind it. With that layer you can search for a word, select and copy text and have a screen reader read it aloud. OCR is not perfect. It can mistake letters that look alike, such as the digit 0 and the letter O, and it struggles with handwriting, crooked pages and faint print. Always check names and numbers it produces.

Some scanning programs and phone apps include OCR, and some free tools add it to existing files. If you are unsure whether your scan has it, test it. Open the PDF, press Ctrl+F, and search for a word you can see on the page. If it finds the word, the file has searchable text. If it says nothing was found, the file is only a picture.

Sharing scanned documents safely

A scanned document often holds sensitive details: an address, an identity number, a signature. Once it is sent, you cannot take it back. Follow a few habits.

• Send only what is needed. If an office asks for one page, do not send the whole file. Scan or export only that page.
• Check who is asking. Scammers pretend to be banks, landlords and employers and ask for scans of identity documents. Contact the organisation through a phone number or website you already know before you send anything.
• Prefer a link with limits to a big attachment. A cloud storage link can be set to expire or to work only for named people. Remove the link when the job is done.
• Name the file clearly and without private details. Use amina-certificate-2026.pdf, not a name that includes an identity number.
• Delete extra copies. Scans sitting in Downloads, in your email Sent folder and on a shared computer are easy to forget. Delete those you do not need, and empty the trash or recycle bin.
• Add a purpose note when you can. Writing across a copy of an ID, in a visible line such as For rental application, 12 March, helps stop it being reused. Keep the note clear of the details that must remain readable.