Stamp Perforation Gauge

ePerforationGauge is an app for measuring, from a picture, the perforation of a stamp that is placed on a black background.

The instructions are simple: Print a document on white paper with a black box in the center of the document where, if the stamp would be placed on, leaves some margin between the stamp and the edges of the black background. Measure accurately the size of the black background and enter this size at the preferences. Place the stamp on the black background and take a picture as close-up as possible. After this, almost immediately the perforation of the stamp is given.

It is extremely important that the width and height are very accurate, at least to one-tenth of a millimeter, otherwise the perforation will not be determined accurately.

Printing a document with a black box of a certain size does not necessarily mean that the black box on paper has that exact size, it will probably somewhat smaller or bigger. Printing the document at the best possible quality will improve the preciseness of the size of the black box on paper.

Tip: You can also calibrate this size by using a stamp with a known perforation. Then tune the width and height until the correct perforation is found.

Do not use protective mounts on the black background because it is very likely that this gives dark shading on the picture which will be interpreted as being part of the black background.

The red lines indicate the area on the edges of the stamp in which the perforation is searched for. The white lines indicate holes, the black lines indicate teeth. Minor perforation irregularities like a missing tooth are corrected and in that case holes and teeth are indicated by a green line.

The small red triangles in the corners indicate how well the black background is recognized. They should be located exactly in the corners, otherwise the reported perforation may not be accurate.

The perforation is reported as T × R × B × L: T is the top perforation, R the right side, B the bottom and L the left side. The perforation is given to the nearest ¼ and with two decimal places. When perforation approximation is enabled then the perforation is approximated to P or H × V when the differences are small enough: P is the overall perforation, H the horizontal and V the vertical. The perforation approximation can be changed in the preferences. When the perforation is very damaged or very irregular then imperfect is reported as the perforation.

The little boxes with the perforation and reference can be placed somewhere else on the screen by dragging these boxes.

Is it that simple? Yes and no. There are restrictions to the picture, background and stamp:

· The edges of the picture must be white, otherwise the black background cannot be found reliably.
· The black background must be reasonably black, not too small and not too much tilted or rotated.
· The edges of the stamp must be reasonably white, the stamp must not be too small and not too much tilted or rotated.
· The stamp must not be imperforated, syncopated or have any other perforation irregularities.
· The stamp must not be triangular, circular or have any other shape other than rectangular.
· The stamp perforation must have a reasonable curved line, very flattened perfs could give a problem.

Use the back of the stamp when the edges are heavily cancelled or when the stamp does not have white edges.

The samples give a good impression of stamps that will give a proper result and especially of stamps that do not.

The best result of a picture is with daylight; using the flash light could make the result of the picture even worse. Because it is the best to make a close-up picture of the stamp, it is required that the camera has a autofocus function, otherwise the result will be very blurred and unusable for the perforation measurement. The best is to experiment to get the best result of the picture.