How to scan or photograph your signature for an online form, 10 to 20 KB

Recruitment and exam forms ask for a signature image that is tiny on both counts: a few hundred pixels wide and 10 to 20 KB. A phone photo of a signature is 3 MB and full of desk, shadow and grey paper. Getting from one to the other cleanly is mostly about what happens before the photo is taken.

Before you photograph it

• Plain white, unlined paper. Ruled lines and the texture of a notebook page survive compression as grey noise.
• A pen with dark, even ink, in the colour the notice asks for (usually black). A ballpoint that skips leaves gaps that look like scanning errors at 140 pixels wide.
• Sign in running hand, the same way as on the form. Several notices, IBPS among them, refuse a signature written in capital letters.
• Sign in a box roughly the shape of the final image: about 7:3 for 140 × 60 pixels, 3:1 for 6 × 2 cm. A tall, narrow signature in a wide frame ends up as a thin line.

Taking the photo

Use daylight from a window or a ceiling light, not the phone's flash, which leaves a bright spot and a dark corner. Hold the phone directly above the page so the paper is a rectangle, not a trapezium, and keep your hand's shadow out of the frame. A flatbed scanner at 200 or 300 DPI gives the cleanest result if you have one; a phone photo in good light is nearly as good once cropped.

Crop tight, then size and compress

Crop to the signature with a little white space around it, so the ink fills most of the frame. Then size and compress in one step: the IBPS preset outputs 140 × 60 pixels between 10 and 20 KB, the SSC preset 6 × 2 cm (472 × 157 pixels at 200 DPI) in the same band. For another portal, enter its pixel size and limits in the fit-to-size tool's options.

Why a signature can be too small

Black lines on white paper are almost all one colour, which JPG stores in very few bytes. A clean 140 × 60 signature can be 4 KB at the highest quality, below a 10 KB minimum. The presets raise quality to the maximum first; if the file is still too small, they add JPEG comment bytes, which every viewer ignores, until it clears the floor. The result row says 'comment bytes added' when that happens. Do not add noise, a grey background or a border to make the file bigger: the portal then shows a dirty signature.

Common problems