The size shown on screen does not tell you how large an image can be printed well. Print quality depends on the file’s pixel dimensions, the amount of cropping, the intended print size, the quality of the original capture and how closely the finished product will normally be viewed.
Start with the pixel dimensions
Check the full-resolution file’s width and height in pixels. Do not use the dimensions of a thumbnail, social-media download or screenshot.
To estimate the print resolution, divide the number of pixels by the intended print dimension in inches:
Pixels ÷ print size in inches = pixels per inch (PPI)
For example, a 6000 × 4000 pixel file produces:
- 20 × 13.3 inches at 300 PPI;
- 30 × 20 inches at 200 PPI.
These figures are a guide rather than a guarantee. A well-focused, carefully processed file may reproduce successfully at a lower PPI when viewed from farther away, while a soft, noisy or heavily cropped file may still disappoint at a higher PPI.
Allow for the crop
Calculate from the pixels remaining after the image has been cropped to the product’s aspect ratio. Cropping away part of the file reduces the number of pixels available for printing.
For example, a panoramic crop taken from a standard camera frame may use only a narrow part of the original image. The uncropped file dimensions can therefore make the image appear more suitable for enlargement than the finished crop really is.
Check the actual crop preview for every size you intend to sell. Do not assume that one calculation applies to every product.
Inspect the file at a useful magnification
Open the final print file in your editing software and inspect important areas at 100% magnification. Look for:
- soft focus or camera movement;
- digital noise, compression artefacts or banding;
- pixelation caused by a small source file;
- halos or an artificial texture caused by excessive sharpening;
- lost highlight or shadow detail; and
- fine details that may not reproduce clearly at the intended size.
Checking at 100% can reveal problems, but remember that a large wall print is normally viewed from farther away. Also zoom out and consider how the complete image will look at a realistic viewing distance.
Grain can be intentional—but check it carefully
An enlargement makes everything in the file larger, including film grain and digital noise. In some photographs, visible grain contributes to the mood and looks appropriate. In others, it can make smooth skies, skin tones, shadows or fine detail appear rough or distracting.
Decide whether the texture feels intentional and supports the image. Do not rely only on a small screen preview: grain that appears subtle on screen can become much more obvious in a large print.
Upscaling cannot recreate missing detail
Upscaling software can increase a file’s pixel dimensions and may improve the appearance of some images. It does not restore detail that was never captured or correct poor focus, camera movement, clipped highlights or heavy compression.
If you upscale a file, inspect the result for invented texture, repeated patterns, unnatural edges and oversharpening before offering the enlarged size.
Make a test print when the result is uncertain
A test print is the safest way to assess a borderline file. Ideally, print the complete image at the intended size. For very large products, you can also print a representative section at the final output scale to evaluate sharpness, grain, colour and detail.
Choose a section containing the detail that matters most, such as a face, fine foliage, lettering, texture or a smooth tonal area. Review it under suitable lighting and from the distance at which the finished product will normally be seen.
Only offer sizes the file can support
If an image does not reproduce well at a particular size, remove that size from the applicable price list or prepare a more suitable file. It is better to offer a smaller print confidently than to sell an enlargement that cannot reproduce the intended detail.
For guidance on preparing the final file and uploading it, see How to prepare and upload images to your Print Shop.
