How to take images the grading can read

A flatbed scanner gives the same scale and the same light across the whole image. A photo does not. If you can only photograph, it still works – read sections 5 and 6.

In our tests the grading missed a detail on one stamp in four at 600 dpi but found it every time at 800. Going above 800 does not help: the grading scales every image down to about 1.2 megapixels anyway, and we store images at no more than 2,576 pixels on the long side.

• Let each image show one stamp. A whole page in one image leaves too few pixels per stamp. If you have many stamps, bulk scan splits one scan into one stamp per image.
• On Windows: use the scanner’s own driver (TWAIN) if you scan above 600 dpi. Windows’ built-in scanning often gives 600 dpi without saying so. That is our experience, not a measurement.

We accept JPEG, PNG and WebP, up to 20 MB and 100 megapixels per image. A scanned A4 page at 800 dpi is about 60 MB as a PNG and is rejected, but about 7 MB as a JPEG. The compression does not affect the measurement.

An object on the glass lifts the lid and makes the image blurrier – the thicker it is, the more. The stamps themselves are thin enough. You do not need a ruler when you scan: the scanner writes the resolution into the file, and that figure is more exact.

Without a ruler or a sheet (section 6) we cannot work out a perforation gauge from a photo.

• Lay the ruler in the same plane as the stamps, with the scale visible.
• An ordinary ruler will do, but not a transparent one. Choose dark marks on a light background, for example a yellow tape measure or a white ruler.
• Let only one scale show. If the ruler has millimetres on one edge and inches on the other, turn it over or crop the inch scale out.
• We recommend millimetres. The tool works out the scale itself when it can, and for small stamps it asks you to choose.

If the camera tilts, the stamp comes out larger at one end than at the other, and the centring assessment compares exactly those margins. So lay the stamps on a white A5, A4 or A3 sheet and photograph the whole sheet. In the measuring tool you click the sheet’s four corners in order around it, starting along a long side, and choose the sheet’s size. The tilt is then removed across the whole image.

• Choose A5 if the stamps fit. The larger the sheet, the fewer pixels per millimetre. Based on our tests, A5 is enough to tell half steps apart in the perforation, while A4 and A3 give a coarser measurement.
• Choose the right size. A sheet of the wrong size gives a measurement that is 30–40 % wrong, and it does not show. A ruler in the same image removes the risk.

• Even light without reflections. A glossy spot carries no information and can be read as damage.
• No hard shadows along the edges. A shadow looks like a short tooth.
• Avoid raking light. It makes the paper’s normal unevenness look like creases.
• Lay the stamps straight, with their edges parallel to the image’s edges and the way up they are meant to be read. A crooked stamp gives too low a gauge, and a stamp on its side gets its horizontal and vertical perforation swapped.

Leave a little background around the stamp. The perforation tips must be fully visible.

Bulk scan finds the stamps by their contrast against the background. A black stock page works for most stamps, but stamps printed on dark paper disappear against it – lay them on something light. Preferably do not mix dark and light stamps in the same scan.

The grading reads the first four images in the listing, so put the front and the back first. The back shows toning, thins and hinge marks, which cannot be seen from the front.

• Stamps and postcards with a start price of €200 or more must have a photo of both the front and the back before they can be published (Terms § 5).
• No image can tell whether a stamp is mint never hinged, because the gum does not show in a flat image. There your own judgement applies.
• If the stamp is in a mount smaller than the stamp, take it out for the image. The mount’s edge can be read as a crease.

• Make the image smaller. Upload the original; we scale it ourselves.
• Edit it. Sharpening and contrast enhancement make the measurement worse, because they move the edge being measured.