Store frames are sold by an opening, not by a pile of A4. A 24 by 36 inch rabbet, or a 50 by 70 centimetre IKEA-style slot, is a hard hole in wood and glass. Fan art that starts as “four sheets wide” almost never lands in that hole. The useful order for rasterbator is the same order a collector already uses at the shop: measure the opening first, then ask the printer to fill it.
Sheet-count posters fail in a specific way. The print can look sharp on the floor and still miss the rabbet by two centimetres. People then shove the stack, crop a face with scissors, or leave a white float that the glass makes obvious. The money already spent on the frame does not move. The reprint does.
Rasterbator is a browser poster maker that splits one JPEG, PNG, or WebP across ordinary sheets and exports a tiled PDF. Exact size is the control that accepts that opening. Width and Height lock the assembled poster. Paper size only describes each printed page. Overlap can help you line up seams without growing the finished rectangle. That is the whole argument. A frame does not care how many sheets you used. It cares whether the picture matches the hole.
Store Frames Sell An Opening Not A Grid
Read the label on the frame, then measure anyway. Outer moulding is advertising. The number that matters is the inner opening, the rabbet that will hide the paper edge under the lip. A “24 by 36” frame can lose several millimetres to that lip. If you print the advertised size and ignore the rabbet, the glass will either pinch the image or show a strip of leftover paper.
Convention weekends and dorm walls make this worse. The frame is already in the suitcase or already hanging. There is no second trip to buy a different size before Friday. The poster has to enter the opening that exists. Sheet count cannot invent that opening. It can only produce a nearby rectangle and hope.
Write the opening on the same scrap you use for the print shop list: width, height, unit. Keep that scrap beside the printer. If the PDF summary and the scrap disagree, the job is not ready. The frame will not negotiate.
Sheet Count Prints Miss The Rabbet
By N sheets wide is honest about its own math. You choose how many sheets sit across, and the tool calculates the height and finished size. That is a good way to see how large a screenshot can become. It is a bad way to fill a bought frame. The second axis is a side effect. The rabbet is not.
The failure is easy to replay. A collector picks four Letter sheets because the photo is wide. The assembled poster comes out a little taller than the frame. They trim the extra from the bottom and cut a credit block or a pair of shoes. Or the poster comes out short, and the opening shows a paper margin that looks like a mistake under glass. Either way, the first stack is discarded. The frame still waits.
When I opened a 50 by 70 centimetre frame after a sheet-count print, the poster looked fine until it sat in the rabbet. Two sides kissed the lip. The other two floated. The image was not warped. It was the wrong object. That wasted an hour of taping and a full reprint. Designers usually blame the printer. The miss started when the grid, not the opening, chose the size.
Shop prints dodge this only if you pay for one sheet at the exact opening. Home tiling can hit the same opening if the finished size is the input. That is the job Exact size is for.
Type The Opening Into Exact Width Height
Set the paper you will actually load. A4, US Letter, or another listed size, plus the orientation the tray can handle. Then continue to poster size and choose Exact size. Rasterbator states the collector rule on that radio: enter the finished size when the poster needs to fit a measured space. Type the opening, not a guessed sheet count.
Use centimetres or inches, matching the tape. Keep image proportions if the art cannot lose an edge. If the source is a square album cover and the frame is 24 by 36, something must crop or float. Decide that on screen. Do not decide it with kitchen scissors after the ink dries.
- Measure the rabbet. Tape across the inner opening in both directions. Record both numbers in one unit.
- Enter Exact Width and Height. Those fields control the assembled poster. Paper still controls each sheet.
- Read the summary. The workspace reports the finished size and the sheet grid together. If the size pair does not match the scrap, change the fields.
- Check Printed sheets, then export. Download the tiled PDF and the Print & assembly guide. Print at Actual Size or 100%.
Measure The Rabbet Not The Outer Moulding
Outer width includes wood you will never see. A tape that rides the moulding invents a poster the glass cannot accept. Measure the visible opening, then subtract a couple of millimetres if you want the lip to cover raw paper edges. Put those reduced numbers into Exact size. The cut guides exist so you can trim to that rectangle. They do not exist so you can discover the opening after printing.
Read Finished Size Before Buying More Paper
This is where the rasterbator stops the reprint loop. The summary is a hang check, not decoration. A line such as 76.0 × 76.0 cm using twelve A4 sheets tells you two facts at once: the object you will assemble, and the labour you will spend. If the object is wrong, more paper will not fix it. If the object is right, page count is just the cost of using a home printer.
Turn off Fit, Shrink, and any automatic scaling. A frame-sized PDF that the driver shrinks to 94% will never ship. The opening stays the same. The picture gets smaller. That is another discarded stack with a clean preview.
Join Sheets Without Changing The Opening
Seams are a separate decision from size. Page margin reserves blank paper around each tile so home printers can leave their hard edges and still keep trim marks. Gap between tiles adds intentional blank space to the finished poster. Overlap repeats a strip of image along adjoining edges so you can align sheets, and it does not change the finished poster size.
A frame almost never wants gap. Gap is a designed float. Under glass it reads as a mistake, unless the art is already a comic-panel grid and you want the slats. Overlap is the usual collector choice: the opening stays the size you typed, and the extra ink is only there to hide a slightly crooked join. Edge-to-edge is finer if you trust your trim. It is also less forgiving when a face crosses a seam.
Overlap Helps Alignment Without Growing The Poster
People treat overlap like extra paper around the whole job. Overlap is a repeated sliver between tiles, not a second border. If the Exact Width and Height already match the rabbet, overlap will not push the poster out of the frame. Gap will. If you need a visible mat, buy a mat. Do not ask the tile gap to impersonate one, then act surprised when the opening shows stripes.
Lay the labeled sheets on the floor in page order before the first cut. If a logo or a pair of eyes sits on a busy join, go back to the workspace. Once a cut guide is gone, that join is permanent. An unreadable seam across a title card is a hard fail even when every page printed clean.
Viewing distance decides style after size is locked. Original Image keeps photographic tone and any small text you still need to read from a metre away. Halftone dots rebuild light and shadow with marks that resolve across a room and look coarse up close. Fan art that will sit over a sofa can take the dots. A poster with a readable title, map labels, or a QR-sized mark should stay Original. The style page does not change the opening. Do not use it as a way to hide a wrong rectangle.
Hang The Print Only After The Opening Matches
Rasterbator belongs in a collector workflow when the frame is already bought and the art has to enter that hole on ordinary paper. Type the rabbet into Exact size, keep gap off unless you want visible slats, print at 100%, and trim to the guides. The sheet grid can change. The opening should not.
Leave the tool alone if you need one shop-printed sheet with no seams, or if nobody will turn off Fit. Exact size cannot rescue a driver that rescales every tile. It also cannot invent a missing measurement. A frame without a recorded opening will still produce a nearby poster and another reprint.
Hang it when the scrap, the PDF summary, and the rabbet say the same two numbers. If they do not, stop. The glass will report the miss faster than any preview tab.
