A hundred photographs on one board

The question is never whether they fit. It is how small each one ends up, and whether that is still big enough to be worth looking at.

Start from the smallest photograph, not the board

Most boards go wrong in the first minute, because the count is decided before the size is. A hundred photographs on a twelve by eighteen inch board is a cell about an inch and a quarter across. That is enough for a landscape, a building or a dog. It is not enough for a group of six people at a wedding, and no amount of arranging afterwards will rescue it.

So work backwards. Decide the smallest a photograph is allowed to be, then see how many of that size the paper holds. The table below assumes square cells with a small gap; oblong ones give you slightly more or slightly fewer, but not enough to change the decision.

Two figures are worth memorising. An inch and a quarter is about where a single face stops being recognisable across a room. Two inches is about where a group of three still reads. Everything smaller than an inch is texture — perfectly good as texture, and a hundred small photographs arranged as a field around six large ones is one of the few ways a board of this size stays interesting rather than exhausting.

The gutter is not decoration

Between two photographs, the gap is what tells the eye they are two photographs. Below about three millimetres on a printed board they start to read as one blurred field, which is why a tightly packed hundred looks worse in print than it does on screen — the screen is showing you the board at a fifth of its real size, where three millimetres is under a pixel.

• Gap between cells: 3 to 6 mm on anything up to A3, 6 to 10 mm on a poster. Enough to separate, not enough to become a pattern of its own.
• Margin at the edge: at least twice the gap. A board that runs to the paper edge loses a few millimetres to trimming and looks accidental where it does not.
• The arithmetic: usable width equals board width, less two margins, less one gap for every column but the last. Divide what is left by the columns and you have the cell. The grid panel does this while you type, and the warning appears the moment the numbers stop leaving room.

There is one exception, and it is the reason free placement exists on this site at all: a deliberate overlap. Photographs that sit on top of each other with no gap, at slight angles, read as a pile of prints on a table rather than a printed grid. It is a different picture entirely and it wants the opposite of everything above — no margin, no rhythm, and depth decided one frame at a time.

Sorting before you place

A hundred photographs dropped onto a board in whatever order the folder handed them over is a hundred decisions you have already lost. Sort first, outside the tool, in whatever file manager you already use: by date if the board is a story, by subject if it is a collection, by dominant colour if it is a pattern. The tray reads them in the order it gets them and the grid generator fills cells in that same order, so the sort you did in the folder is the sort you get on the board.

Then place the large ones by hand before anything else. Three or four photographs at twice the size of the rest, spread unevenly, give the eye somewhere to land. Fill around them afterwards — and if a gap will not close, an eighty-fifth photograph is nearly always easier to find than a clever rearrangement of the eighty-four you have.

What a hundred photographs cost the browser

Worth knowing, because it explains a thing you will see. A hundred twelve-megapixel photographs decoded at full size is about five gigabytes of pixels, which no browser tab will hold. So each one is kept three ways here: a 256-pixel thumbnail that lives for the session, a 1,600-pixel copy the screen draws from, and the file itself, which is read again only when you export.

The middle copy is the one that gets dropped when memory runs short, oldest first. When that happens the frame falls back to its thumbnail for a moment and then sharpens again, which is the flicker you occasionally catch after scrolling a long tray. Nothing about the document changed; the export reads originals regardless of what the screen was showing.

None of this makes the export instant. On a 7,200 by 10,800 board with a hundred and sixty frames, reckon on the order of a minute on a laptop and longer on a phone — that is arithmetic from the pixel count rather than a stopwatch held to your hardware, so take it as a shape and not a promise. Every original is read again at full resolution to draw it, and the progress figure on the button is the honest one: there is no faster path hiding behind it.

Questions this raises

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