Quick printing guide

Quick Printing guide

The purpose of this guide is three-fold:

  • Show you how to find the appropriate image resolution (in DPI/PPI, cf. below) for a minimum quality print
  • Show you how to calculate the maximum print size for a given image size in pixels (small, medium, high-resolution, etc)
  • Show you how to find the required image size in pixels for printing at a specific size (15x10cm or 6x4”, 18x13cm or 7x5”, etc)

If you are not interested in calculations or explanations, please refer to the Reference table at the end of this guide for a quick lookup.


Pixels: fundamental units of digital images

All digital images are measured in pixels, the smallest building block to create an image on screen, which stands for “picture element”.

The offered pixel dimensions are indicated in the Personal Use Download Pricing dialog before the currency in CHF, starting with the longest edge of the image. For example:

1024x681 pixels

1920x1278 pixels

2560x1703 pixels

4256x2832 pixels


What is DPI/PPI and what it means for printing

To prepare digital images for printing, we need to determine the resolution of an image which is measured in DPI/PPI.

The terms DPI (dots per inch ) and PPI (pixels per inch) are used interchangeably by error.

DPI stands for dots per inch and refers to the resolution of a printer. It describes the density of ink dots placed on a sheet of paper (or another photographic medium) by a printer to create a physical print. DPI has nothing to do with anything displayed digitally!

PPI refers to the number of image pixels from the digital file that will be used to create one inch on the printed medium. PPI is the more straightforward of the two terms. It describes just that: how many pixels an image contains per inch of distance (horizontally or vertically). PPI is also universal because it describes resolution in a way that doesn't vary from device to device.

Whenever you encounter the terms DPI/PPI together in the context of digital printing, they will refer to the number of image pixels that will be used to create one inch on the printed medium.

Generally, the higher the DPI/PPI, the higher resolution the image and the more detail will be in the final print.

If you want a more detailed explanation of the confusion around DPI / PPI, please refer to the Useful links at the bottom of the page.


Do I always need to print at 300 DPI/PPI?

Most printing labs will print images with the 300 DPI setting, but this is not a requirement.

For historical reasons, the setting of 300 DPI has been chosen to produce the best image resolution for hand-held prints, namely prints that are viewed at a distance of 60cm or less.

When assessing your DPI/PPI requirement, the main thing to take into account is the viewing distance.

Viewing distance affects your required resolution simply because if you stand further away from an image then the pixels get smaller. A billboard is rarely viewed closely so a resolution of 20-50 DPI will probably be fine. But the key point is to take into account how far away the viewer will be.

Here's a handy little chart to help you decide on a suitable resolution. It is based on someone with good eyesight.


Viewing Distance

Min Resolution

0.6m / 2ft

300 dpi

1m / 3.3ft

180 dpi

1.5m / 5ft

120 dpi

2m / 6.5ft

90 dpi

3m / 10ft

60 dpi

5m / 16ft

35 dpi

10m / 33ft

18 dpi

15m / 50ft

12 dpi

50m / 160ft

4 dpi

60m / 200ft

3 dpi

200m / 650ft

1 dpi


The recommended resolution range for best results on inkjet printers, depending on viewing distance and print sizes runs from 300 DPI to 140 DPI.


How do I calculate the maximum print size for a given pixel dimension (image size)?

Let’s say you purchased the medium image size with a pixel dimension of 1920x1278 pixels and your DPI setting is set at 300, based on your viewing distance (hand held print)

Apply the following calculation :

1920 pixels / 300 DPI x 2.54 cm (to convert to metric) = 16.25 cm maximum width

1278 pixels / 300 DPI x 2.54 cm (to convert to metric) = 10.82 cm maximum height

If you are allergic to maths, use either one of the following 3 online calculators:

Go to this page: https://prinfab.com/blog/viewing-distance-and-dpi/#image-sizing-calculator

In the Image Size Calculator, delete the default DPI to clear all values

1. Entre the pixel dimensions (image width = 1920 and image height = 1278)

2. Enter the viewing distance in cm, for example, 60 cm and press Enter

3. The calculator will display the maximum print size in cm and in inches

Or

When you know exactly what DPI value you are expected to use for the print, you can use this pixel converter:

https://www.blitzresults.com/en/pixel/

Click on Pixels <--> Centimeters, enter the pixel values (width then height) and select 300 DPI. Click the Calculate button for results to obtain the maximum print size at 300 DPI.

Or this pixel calculator : https://www.pixelcalculator.com/index.php?lang=en

1. Click “Clear all” button in red to delete all values

2. In the center column, enter the length (width) and the height in pixels

3. Enter the required resolution, namely 300

4. Click the calculate button to obtain the maximum print size

The results indicate the maximum print size for your 300 DPI is 15 x 10 cm (6x4”).

If you wish to print at a slightly bigger size, let’s 18x13 cm (7x5”), you will need to decrease your DPI to 240.

1920 pixels / 240 DPI x 2.54 cm (to convert to metric) = 20.32 cm maximum width

1278 pixels / 240 DPI x 2.54 cm (to convert to metric) = 13.52 cm maximum width

Note that 240 DPI for small and medium-sized prints is quite acceptable.


How do I find the required pixel dimensions for a specific print size and DPI?

Use this pixel converter at https://www.blitzresults.com/en/pixel/ and choose the option:

Centimeters to Pixels

1. Enter the width of the print in cm (eg. 15)

2. Enter the height of the print in cm (10)

3. Specify the DPI setting, namely 300

4. Click the calculate button to find the required pixel dimensions for the image.

The required pixel dimensions are 1772x1181 pixels

Or, using this online pixel calculator: https://www.pixelcalculator.com/index.php?lang=en

1. Click “Clear all” button in red to delete all values

2. In the first column (left), enter the length in mm (width), namely 150mm

3. In the second row of first column, enter the heigh in mm , namely 100mm

4. Enter the desired DPI = 300

5. Click calculate

The required pixel dimensions are 1772x1181 pixels

You can also use this calculator “Desired Image Size Goal” if you want to work with inches:

https://www.scantips.com/calc.html

If you are avert to calculations and are unsure about the final viewing distance, please use this table as a target reference to help you choose the required DPI/PPI:

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Reference table

The table shows, for common print formats, the minimum recommended resolution in DPI/PPI and the minimum required sizes of the corresponding digital images in pixels:

Print Format

Common Usage

Minimum recommended

Image Size

Name

Size (width x height)

inches

DPI/PPI

pixels

A6 (ISO-216)

105 mm x 148 mm

4.13” x 5.83”

books, postcards

300

1487 x 2099

A5 (ISO-216)

148 mm x 210 mm

5.83” x 8.27”

books

300

1749 x 2481

A4 (ISO-216)

210 mm x 297 mm

8.27” x 11.70”

letters, magazines, catalogues

240

1985 x 2808

A3 (ISO-216)

297 mm x 420 mm

11.70” x 16.54”

posters, newspapers

200

2340 x 3308

A2 (ISO-216)

420 mm x 594 mm

16.54” x 23.40”

posters

180

2977 x 4212

A1 (ISO-216)

594 mm x 841 mm

23.40” x 33.11”

posters

160

3744 x 5298

A0 (ISO-216)

841 mm x 1189 mm

33.11” x 46.81”

posters

140

4635 x 6553

4R

102 mm x 152 mm

4” x 6”

photographs

300

1440 x 2160

5R

127 mm x 178 mm

5” x 7"

photographs

300

1500 x 2100

8R

203 mm x 254 mm

8” x 10"

photographs

240

1920 x 2400

203 mm x 305 mm

8” x 12”

photographs

240

1920 x 2880

ANSI – A ( ≈ A4 )

Letter

216 mm x 279 mm

8½” x 11”

posters

240

2040 x 2640

Legal

216 mm x 356 mm

8½” x 14”

240

2040 x 3360

14R

11” x 14"

photographs

200

2200 x 2800

ANSI – B ( ≈ A3 )

Tabloid

279 mm x 432 mm

11” x 17”

posters

200

2200 x 3400

305 mm x 457 mm

12 x 18”

200

2400 x 3600

330 mm x 483 mm

13” x 19”

200

2600 x 3800

406 mm x 508 mm

16” x 20"

180

2880 x 3600

406 mm x 619 mm

16” x 24”

180

2880 x 4320

ANSI – C ( ≈ A2 )

432 mm x 559 mm

17” x 22”

posters

180

3060 x 3960

Broadsheet

457 mm x 610 mm

18” x 24”

posters

160

2880 x 3840

508 mm x 610 mm

20” x 24"

140

2800 x 3360

508 mm x 762 mm

20” x 30”

140

2800 x 4200

ANSI – D ( ≈ A1 )

559 mm x 864 mm

22” x 34”

posters

140

3080 x 4760

610 mm x 914 mm

24” x 36”

posters

140

3360 x 5040

689 mm x 991 mm

27” x 39”

posters

140

3780 x 5460

ANSI – E ( ≈ A0 )

864 mm x 1118 mm

34” x 44”

posters

140

4760 x 6160


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References and Useful links:

Online calculators

Image Sizing Calculator

https://prinfab.com/blog/viewing-distance-and-dpi/#image-sizing-calculator

Pixel conversions

https://www.blitzresults.com/en/pixel/

Online Pixel DPI Calculator Converter Conversion

https://www.pixelcalculator.com/index.php?lang=en

Resolution DPI calculator for printing digital images

https://www.scantips.com/calc.html


Viewing distance and DPI

DPI and Viewing Distance - What DPI should I choose?

https://prinfab.com/blog/viewing-distance-and-dpi/#what-settings-should-i-use

What's the correct DPI for printing? Short answer

http://resources.printhandbook.com/pages/dpi-for-printing.php


Dispelling the DPI and PPI confusion

Difference between DPI and PPI

https://www.andrewdaceyphotography.com/articles/dpi

DPI vs PPI

https://photographylife.com/dpi-vs-ppi

Dispelling the 72 dpi myth

https://www.andrewdaceyphotography.com/blog/tech-tuesdays/dispelling-the-72-dpi-myth

Understanding Resolution; PPI, DPI for Print and Digital

https://youtu.be/QveT_6BQ72o

Quality of Image Prints

http://connoisseurimages.com/Quality_of_Image_Prints_a.html

(In French) Quelle résolution pour un tirage?

https://www.tirages-pro.com/blog/2011/06/quelle-resolution-pour-un-tirage/

(In French) Pour en finir avec les 72 DPI sur Internet

http://blog.arnaudfrich.com/photo/pour-en-finir-avec-les-72-dpi-sur-internet/

(In French ) « Le guide pratique des dpi, comprendre et bien utiliser les dpi »

http://blog.arnaudfrich.com/photo/pdf-c-est-quoi-les-dpi/

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