How to print a digital download at home or at a print shop

A digital download gives you a portrait as a file, and you decide how, where and on what it gets printed. This page lists the steps in order: check the file, choose the size and shape, pick a home printer or a print shop, set up the printer, make a test print, and let the print dry. It also lists the questions to ask a print shop. It belongs to the guide to art prints and paper, whose other pages explain each choice in more depth.

Step 1: check the file

Before you print, open the file and look at three things: its pixel size, its format and its shape.

Pixel size. The University of Chicago Press, in its guide for authors, says the pixel dimensions appear in the file's properties and in most photo editing programs. Divide each side by the pixels per inch you want to find the largest print. The page on print resolution explains the numbers and has a calculator for the four Purrealism sizes.

Format. Image files come in several formats, and they handle quality differently:

If your download is a JPG, print from the original file. The press advises against editing or re-saving a JPG before it goes to print, and suggests keeping a copy of the original as a backup. If you want to make changes, save your edited version in a lossless format such as TIF or PNG.

Shape. Reduce the pixel width and height to a ratio, such as 3:4 or 2:3, and compare it with the paper. The page on print sizes and shapes shows how much each shape loses at each size.

Step 2: choose the size and what to do with the edges

When the image and the paper have different shapes, you have two choices. Fill the paper and trim two opposite edges of the image, or print the whole image and leave blank borders. Decide which one before you print, because the choice changes what appears at the edges.

A home printer limits the size. The University of Illinois Library's preservation guide says many inkjet prints in collections measure 8.5 × 11 inches or less. That is the US Letter format, which Markus Kuhn's guide to paper sizes at the University of Cambridge gives as 216 × 279 millimetres, half of a 17 × 22 inch basic sheet. An 8 × 10 inch print fits on that sheet with 0.25 inches to spare at each side and 0.5 inches at the top and bottom. The three larger sizes, 12 × 16, 18 × 24 and 24 × 36 inches, need a wider printer, which usually means a print shop.

Home printer or print shop

Size is one difference between a home printer and a shop printer. The ink set is another. The Image Permanence Institute says the most basic inkjet printers use four inks, cyan, magenta, yellow and black, while some high end printers add lighter inks such as light cyan, light magenta and greys, and extra colours such as orange, red, green, blue or violet, to widen the range of colours they can print. It dates wide format inkjet printing, for sheets wider than a desktop printer takes, to 1993.

The type of ink differs too. The University of Illinois guide says dye inks are cheaper and are used more widely in home and office printers, while pigment inks are more lightfast and resist water better. If your home printer uses dye inks, a print from it will need more care than a pigment print. Ask a print shop which kind it uses, and check your own printer's ink cartridges before you print.

Step 3: choose the paper

The paper matters as much as the printer. The Image Permanence Institute at Rochester Institute of Technology says plain paper absorbs ink in ways that dull the colour and soften the lines, so inkjet photo and art papers carry a coating that keeps the ink near the surface. The University of Illinois guide adds that the amount of ink in a picture usually makes plain paper cockle, meaning wrinkle and wave, and that commercially produced prints are usually made on coated papers.

Match the paper to the ink. The Institute says polymer-coated papers, which swell to take in the ink, are used with dye inks, because many pigment particles are too large to enter the coating. Porous-coated papers take both dye and pigment inks. The pages on matte and glossy paper and archival paper and inks explain these choices.

Step 4: set up the colour

Send the printer the colours it expects. The International Color Consortium, the group of companies behind the colour profile standard, says many printers have only an RGB interface. If you send them CMYK data, they convert it back to RGB before separating it into their inks, which can give a worse result. For these printers the Consortium advises leaving the file in RGB.

The Consortium also explains where colour profiles come from. A printer profile relates the printer's colour numbers to a standard colour space, and most profiles come from the device's manufacturer. On cheaper desktop printers, the profile is usually applied by the software that sends the job, such as a photo editor. The page on colour spaces for printing explains sRGB, Adobe RGB and profiles.

Step 5: make a test print

A small test print shows problems before you use a large sheet. Check three things on it:

1. Sharpness. Rollins College's library suggests zooming to "actual size" or 200 percent on screen to look for blur, distortion or visible squares, and a test print shows the same things on paper.
2. Colour. Look at the test print in the room and the light where the portrait will hang.
3. Edges. Check whether the trim or the borders fall where you expected.

SUNY Broome's library gives one more check with the free GIMP editor: choose Image, then Print Size, and set the resolution to 300 pixels per inch. The size shown is the largest that prints well. It also warns that an image that looks good on a screen will not necessarily print well.

Step 6: let the print dry

A fresh inkjet print needs time. The Image Permanence Institute says polymer-coated papers can take from several minutes to several hours to dry fully, and that handling them while wet can smudge the ink. It advises letting every print dry fully after printing before it is stacked or interleaved with other sheets, to prevent spots, changes in surface shine and sheets sticking together. The University of Illinois guide says swellable papers can take up to 24 hours to dry completely, while porous papers dry at once.

Once dry, keep the print flat and covered until it is framed. The page on storing unframed prints covers sleeves, boxes and handling.

Questions to ask a print shop

The Image Permanence Institute recommends describing a print by its colorant, process, coating and support, in that order, for example "pigment inkjet on porous-coated baryta paper". Use the same order for your questions:

• Which ink do you use, pigment or dye?
• Which process: inkjet, or another method?
• Which paper and coating, and what is its weight in g/m²?
• Which file format and colour space do you want?
• Will you trim the image or add borders at this size?
• Can you make a small test print first?

The giclée printing page explains the word many shops use for inkjet art prints, and the paper weight page explains the g/m² figure.

What this means for a royal pet portrait

Purrealism offers each portrait as a digital download or as an art print in four sizes, 8 × 10, 12 × 16, 18 × 24 and 24 × 36 inches, on matte or glossy paper. You choose between them in the portrait studio. The download gives you the steps on this page. The art print leaves only the size and finish to choose.

Portraits with fine detail reward a careful test print. The Indian Royalty portraits in the gallery include a golden retriever wearing a royal crown and red robe, and small details such as a crown are the places to look for blur on a test print.