Field guide

Print sizes and DPI for India: A4, A3, 4 × 6 in and chart paper

Paper size times DPI gives pixels: an inch at 300 DPI is 300 pixels. The board works the other way round too — keep the paper, change the DPI, and the pixel count moves while the printed size stays put.

A4 (21 × 29.7 cm, ISO 216) at 300 DPI is 2480 × 3508 px. It is the size most school projects, forms and cyber-café printers expect, and the size list offers it as a chip before the first photo.

A3 (29.7 × 42 cm) at 300 DPI is 3508 × 4961 px, and A5 (14.8 × 21 cm) is 1748 × 2480 px. Both are ISO sizes, so any print shop will recognise them.

4 × 6 in, the common photo-lab print, is 1200 × 1800 px at 300 DPI; 5 × 7 in is 1500 × 2100 px. These are common lab sizes rather than a standard, so the size list labels them 'check'. The passport sheet mode lays its copies on a 4 × 6 in or an A4 sheet.

Chart paper is listed at 22 × 28 in, drawn at 200 DPI (4400 × 5600 px) to keep the file workable. Supplier sizes vary, so measure yours and type it in as a custom size if it differs.

PNG and JPEG exports carry the board's DPI inside the file (a pHYs chunk in PNG, JFIF density in JPEG), so print software opens a 12 × 18 in board at 12 × 18 in instead of reading 72 DPI and showing something four times the size.

For a cyber café, export PDF: the page is set to the paper size, so 'actual size' printing gives the right dimensions. Ask for 'actual size' or '100%', not 'fit to page'.

Home inkjets cannot print the last few millimetres of an A4 sheet. Turn on Fit to printer margins in the export settings to shrink the whole picture evenly inside a 5 mm margin (or your own figure) so nothing is clipped.

Colour is sRGB and is not converted to CMYK. If colour must match exactly, give the print shop the original photos too; the board will say when a source photo was CMYK.