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Guide to Image Resolutions

Viewing an image is very important. If the image is not clear, then the viewer cannot accurately see the image. This is described as image resolution. When measuring the image resolution, pixels are needed to grasp the entire image. A pixel is defined as the smallest unit that can be controlled on the picture. Each pixel has its own address. The address of the pixel corresponds to coordinates. Pixels are normally arranged in a two dimensional grid, and represented using either dots or squares. Each dot or square is one pixel and one pixel is a sample of the entire image.

In order for the image resolution to be accurate, there must be a certain number of pixels width and length wise on the image. These are called resolutions and are listed as the number of pixels in the width x the number of pixels in length.

Below are five image resolutions offered on our website:

Many digital cameras express resolution in term of Megapixels (MP).  For example, a Nikon D70 is a 6.1 MP camera; when taking a picture at the highest resolution setting of the camera the image will have about 6.1 million pixels in it.  To determine the MP in an image, multiply the number of pixels in the width by the number of pixels in length.

For instance, the 5 resolutions we offer on our site have the following MP

Pixels
in width

Pixels
in length

Total number
of pixels

Megapixels

192

x

128

=

24,576

=

0.02

384

x

256

=

98,304

=

0.10

768

x

512

=

393,216

=

0.39

1536

x

1024

=

1,572,864

=

1.57

3072

x

2048

=

6,291,456

=

6.29


Now that you know how many pixels you have, the next step is deciding what size will it be when it is used. Every output has a certain resolution associated with it, often expressed as pixels per inch or PPI. PPI is different than dots per inch or DPI. DPI refers to the amount of toner or ink used per inch of paper. Despite this difference, many computer programs use DPI as a crude guideline to approximate the PPI. Here is a brief list of PPI outputs:


Output Type

PPI

Computer monitors

72-96

Video Projectors

Depends on the  distance from the screen

Commercial printing

300


To find out the maximum size that a given image can be displayed or printed at without distortion, divide the dimensions in pixels by the PPI for the output.  Here are 2 examples for our resolutions:

Displayed on a computer monitor at 72 PPI

Pixels
in width

Pixels
in length

Maximum Width
(inches)

Maximum Height
(inches)

192

x

128

2.7

x

1.8

384

x

256

5.3

x

3.6

768

x

512

10.7

x

7.1

1536

x

1024

21.3

x

14.2

3072

x

2048

42.7

x

28.4


Printed commercially at 300 DPI

Pixels in width

Pixels in length

 

Maximum Width (inches)

 

Maximum Height (inches)

192

x

128

 

0.6

x

0.4

384

x

256

 

1.3

x

0.9

768

x

512

 

2.6

x

1.7

1536

x

1024

 

5.1

x

3.4

3072

x

2048

 

10.2

x

6.8


This gives you guidelines for the maximum size if you plan to use the entire image. You can always choose to make the image smaller than the maximum size without worrying about distorting the image. If you choose to make the image larger, you run the risk of reduced quality in your final product. It is also important to note that if you plan to zoom in on a portion of the image and enlarge it to show a certain feature, you will need a larger image to start with since you will be ultimately reducing the number of pixels in the image when you crop it.