Photo Card Maker

Open a shop-bought greeting card flat and it is one sheet with one crease. Make a card at home and that sheet has to come out of a printer first, which is where the trouble starts.

The printer knows nothing about folding. It lays ink on a flat page, so every panel of the finished card has to sit on that page in the place, and facing the way, that the fold will later put right. Get one panel wrong and the greeting inside reads upside down, or the back cover lands on the front. None of this is a matter of taste. It is geometry, and it can be checked before any paper is spent.

One sheet, four panels

A card has four panels: a front, a back and two that face each other inside. The simplest way to get them is to fold a sheet once. Letter paper is 8.5 by 11 inches and A4 is 210 by 297 mm, so a half fold gives a card of 5.5 by 8.5 inches, or 148.5 by 210 mm. The outside of the sheet carries the back on the left and the front on the right, and the inside carries the two inner panels. Both sides are printed, which means the sheet goes through the printer twice, or once through a printer that can turn it over.

The other way prints one side only and folds twice. Matt Roberts and Don Etherington, in their dictionary of bookbinding, give the name French fold to a sheet printed on one side only and folded so that the inside of the fold is blank. Their entry for quarto supplies the geometry: sheets folded twice, the second fold at right angles to the first. A quarter-fold card is exactly that, made at a desk.

The price of printing one side is size. Each panel is a quarter of the sheet, 4.25 by 5.5 inches from Letter and 105 by 148.5 mm from A4. The reward is that nothing has to be turned over, and the unprinted side vanishes into the fold.

Paper size decides the shape. In the ISO system every sheet has a height to width ratio of the square root of two, so an A4 sheet folded in half keeps its proportions. Letter does not. Its half is 1.545 times as tall as it is wide, and its quarter 1.294.

Why the top row is upside down

Hold a Letter sheet upright with the print toward you. The quarter fold sends the top half behind the bottom half, then the left half behind the right. Follow the bottom right panel: it never moves, so it is the front, and it is printed upright. The bottom left panel swings round behind it and becomes the back. The two top panels go over the first fold, which turns them head over heels, and they finish facing each other in the middle of the stack. Anything printed upright on them would stand on its head when the card is opened. So they are printed upside down, and the fold sets them right.

There is a second twist. The panel a reader sees on the left of the open card is printed at the top right of the sheet, and the right-hand panel at the top left. The first fold turned them over, and turning a thing over swaps its sides.

The tool on this page does not take any of that on trust. It treats the four panels as rigid pieces, carries them through both folds, and then looks at the result the way a reader would: closed from the front, turned over, and opened flat. Four panels can sit in 24 orders, and each can be upright or inverted, which makes 384 arrangements. Exactly 1 of 384 folds into a card that reads correctly, and it is the one just described. Turn any single panel and the check fails.

A card that opens upward, with the fold along the top, comes from the same sheet laid on its side. Run the same check and three of its four panels turn out to be printed upside down. Only the front stays upright.

The half fold has a quieter version of the same thing. With the fold on the left, all four panels are upright. With the fold along the top, the back is printed upside down above the front, because it travels over the fold to face the other way.

Paper that will take a fold

Card stock is sold by weight, and the numbers mislead. The dictionary defines basis weight as the weight of a ream, normally 500 sheets, cut to a basic size, and that size changes with the grade. Book papers are weighed at 25 by 38 inches and cover papers at 20 by 26. A 65 pound cover sheet is therefore nearly twice as heavy, area for area, as a 65 pound book sheet. Most other countries skip the puzzle and give grams per square meter. Common uncoated cover papers run to 50, 65 and 80 pounds, and the dictionary says the class generally has good folding characteristics.

Machine-made paper also has a grain. The machine direction is the way most of the fibers lie, and the sheet is stronger along it. A fold at right angles to that direction is against the grain. Of books, the dictionary says a well-produced one always has the grain running from head to tail, so that the binding fold is not against it. A quarter-fold card creases in both directions, so one of its two folds always fights the grain.

The remedy is the score: a crease pressed into heavy paper along the line of the fold before it is bent. It compresses the fibers into a hinge and increases the number of times the sheet can be flexed before it fails. A dull blade will do it. In binding, the dictionary notes, scoring is frequently necessary because of the weight of the paper, a wrong machine direction, or both.

Edges, pixels and the second side

A photograph that runs to the edge of a card is a bleed, which the dictionary defines as a printed image that runs off the edge of a page, and also as the deliberate trimming that makes one. The picture is printed larger than the card and the excess is cut away. This tool adds 1/8 inch on Letter and 3 mm on A4, draws corner marks outside that, and cuts a Letter half fold to 10 by 7 inches, which folds to 5 by 7. Choose a white border instead and nothing is cut. The card is the whole sheet.

Pixels are plain arithmetic. A resolution is a count of dots per inch, so a print needs its size in inches multiplied by that count. Try it above: choose Half fold, Letter and Full bleed, leave the resolution at 300, and the readout gives a front of 1500 by 2100 pixels, 3.15 million in all. A photo of 3000 by 2000 pixels, set to the Full photo layout, has to cover the 7.25 inch height of the front and its bleed with its 2000 pixel side. That is 276 pixels per inch, and the tool reports it as short of 300.

A photo file can also carry an orientation in its metadata, such as EXIF, saying how far the stored picture must be turned to stand upright. The tool honors that note when it opens the file, so a portrait arrives as a portrait.

The half fold needs its second side, and there are two ways to turn a sheet. The Internet Printing Protocol names both. With two-sided-long-edge the pages suit a reader as if for binding on the long edge, sometimes called duplex or head-to-head. With two-sided-short-edge they suit binding on the short edge, sometimes called tumble or head-to-toe. The CUPS documentation adds that the short-edge setting suits landscape pages and the long-edge setting portrait ones. A half-fold card is one wide spread on each side of the sheet, so it wants the short edge. The fold check agrees: with the long-edge flip the inside panels come out upside down.

A printer without automatic duplex leaves the turning to you. The sheet is printed on one side, taken out, turned over by hand and fed through again, and it is up to the person at the tray to put it back the right way round. One plain sheet settles it.

Envelopes, postcards and what a file cannot promise

A card wants an envelope, and the sizes pair up. An A4 sheet folded once is A5 and fits a C5 envelope, 162 by 229 mm. Folded twice it is A6 and fits C6, 114 by 162 mm. Letter paper folded twice goes into an A2 envelope, 4 3/8 by 5 3/4 inches, and folded once into an A9. The trimmed 5 by 7 inch card slides into an A7, which measures 5 1/4 by 7 1/4 inches.

A postcard is the unfolded case, and here the rules belong to someone else. The Printer Working Group’s list of media names gives 4 by 6 inches the alias postcard. The United States Postal Service allows its card price only for pieces at least 3 1/2 by 5 inches and 0.007 inch thick, and no more than 6 by 9 inches and 0.016 inch thick. Above 4 1/4 by 6 inches the minimum thickness rises to 0.009 inch. Bristol board, by the dictionary’s account, starts at 0.006 inch, so thin stock can fall short.

The same manual defines an address side and, for some prices, how it is divided. The back this tool draws, with its rule, four lines and stamp box, is a convenience. It promises none of that.

The limits are just as plain. A file cannot know how close to the edge your printer can lay ink, or how exactly it feeds the same sheet a second time, so borders on the two sides may not line up. The fold check is rigid. It gives paper no stiffness and no thickness beyond a gap between layers, so it proves where each panel ends up and which way it faces, not that a particular stock will crease without cracking.

So print one copy on plain paper first. Fold it, open it, turn it over. If the greeting faces you the right way up, the geometry held, and the good paper can go in.