Printing your images — how to properly prepare and print your images
Printing an image requires more thought and preparation than printing a document. It’s not difficult, you just need to be aware of a couple of extra steps…
- Sizing for print
- Setting the correct colour profile
- Final sharpening
Sizing an image for printing
The first (and most important) task is to make sure you have enough pixels. That might sound obvious but it’s the most common error people make. It’s also the biggest reason why photographers are often disappointed with their finished prints.
How do you know if you have enough pixels?
You need to know two pieces of information…
- Physical size of the finished print
- How many dots per inch (DPI) your printer needs
Let’s look at these in turn.
Physical dimensions are easy to find. It’s the size of the media you load in the printer or, if you’re using a print on demand service, the size of the print you’re planning to order. It might be quoted in inches, centimetres or millimetres but because DPI references inches, you’ll make life a lot easier for yourself if you use inches.
DPI is a printing acronym that stands for Dots Per Inch and it means just that: the number of dots (the term printers use for pixels) that the printer will print per inch of paper. I’m not going to go into all the fine detail about DPI here so if you’d like to know more, check out this article: Dots per inch – Wikipedia
Common DPI values are…
| Print Quality | Typical DPI range |
|---|---|
| High | 300 to 600 |
| Medium | 150 |
| Low | 72 |
DPI is often mistaken for resolution. It’s not! The resolution of an image is actually the number of pixels it contains. DPI is only relevant when printing a hard copy and has no bearing on electronic display devices. Changing the DPI of an image from, say, 300 DPI to 72 DPI won’t make any difference whatsoever unless it’s printed.
What DPI value should you use?
Most print on demand services use a DPI of 300 for a good quality print without needing too large acceptable file size. 250 DPI and 600 DPI are also commonly used so it’s best to check with the service provider to see what they require.
Similarly if you’re using your own printer, values of 300 and 600 are commonly used but you should check the manual to ascertain the value you need.
Putting it all together…
Now you know the hard copy dimensions and the DPI, multiply them together to get the number number of pixels you need. For example…
If you want a 12″ x 8″ print at 300 DPI you will need an image size of at least 3600px x 2400px
12″ × 300dpi = 3600px
8″ × 300dpi = 2400px
For a 6″ x 4″ print at 250dpi you’ll need at least 1500px x 1000th
6″ × 250dpi = 1500px
4″ × 250dpi = 1000px
For a 20″ × 30″ canvas printed at 240dpi your image needs to be 4800px x 7200px
20″ × 240dpi = 4800px
30″ × 240dpi = 7200px
Printing better colours — setting the correct colour profile
Have you ever sent an image to print only to find it has weird colours? Or come back too dark or washed out?
If so, the chances are your image had the wrong colour profile. Most images use a colour space called sRGB. It’s the default for many DSLR and compact cameras alike. It’s also the most prevalent around the internet too and use by many print on demand services but not all. Some use CMYK instead.
If your colours are looking weird, you’ve probably sent an sRGB file for printing and the printer needed CMYK
How do you know what to use? Check the printer or print on demand service’s documentation to find out.
Output sharpening…
Most photographers get sharpening wrong. It’s not because they do it wrong (although I’ve seen more than my fair share of crispy fried feathers because the photographer has over sharpened the image) it’s because they do it at the wrong time.
Sharpening should be the last thing you do to an image. After you’ve sized for printing, then, and only then, sharpen for printing.
If you sharpen first then resize, you’re in danger of damaging the image fidelity and creating something dreadful. Not the beautiful image you or your customer wanted to hang on the wall.
