The quality of a digital picture is largely dependent upon the number and size of the digital camera pixels contained in
the image. The Image resolution is simply the information about the pixel density of the image. Higher resolution images
can be printed to larger sizes with less loss of image quality than low resolution images.
For reference purposes, there is a photo enlargement chart below that will give you an idea of the best image resolution
needed for various photo print sizes.
What are Pixels? The word Pixel is a shortened and combined version of the words Picture and Element. Every digital
camera contains a device called the image sensor which has millions of light capturing cells. The light captured at each
cell location is called a digital camera pixel. For the record, there are one million pixels in a megapixel.
Digital Single Lens Reflex cameras like the Nikon D5300 have larger image sensors than a digital compact camera like
the Canon Powershot ELPH 130 HS. The larger sensors produce larger pixels which leads to higher quality images.
The colors and light intensity for each of the millions of individual pixels appear to be blended together when we view
them as a print picture or on a computer screen. Picture 1A below is an ordinary picture taken with a compact digital
camera. Picture 1B shows a portion of picture 1A with the pixels greatly magnified and exaggerated so you can see how
pixels form an image. However, there will be thousands or millions more pixels in an area equivalent to picture #1B when
you take your pictures.
Image File Size: The file size of an image is expressed by the total number of pixels in the width and height of an image.
For instance a file size might be written as 3,456 X 2,304. That will mean there are 3,456 pixels in each row of pixels in
the image from left to right and 2,304 pixels in each column of pixels from top to bottom.
To find the total # of pixels in an image, just multiply the # of pixels in the width of the image by the # of pixels in the
height of the image. (3,456 X 2,304=7,962,624 ) Usually the total amount of pixels is rounded up or down to the nearest
megapixel. So in this case the image might be called an 8 Megapixel picture although it does not contain a full 8 million
Although digital cameras are often marketed with emphasis on the total # of megapixels available for an image, they all
have settings which allow the photographer to take pictures with smaller file sizes. That feature can save space on your
cameras memory card or in your computer hard drive. Also, images with smaller file sizes are easier to send and
download when using email. Taking pictures at different file sizes will make more sense as you continue to read about
image resolution and print sizes.
Image Resolution: In general terms, image resolution in digital photography refers to the amount of information
contained in an image file. That information is the amount of pixels contained in any digital picture you take. A picture file
size 4,000 x 3,000 will have a higher picture resolution than a file size 2,000 x 1,500. Higher resolution pictures will be
sharper, clearer, and more accurately reproduced when printed, or when they are viewed on a computer screen.
More specifically, image resolution refers to density in terms of Pixels Per Inch (PPI) or Dots Per Inch (DPI) rather than
the size of the whole file. Sometimes the terms PPI and DPI are often incorrectly used interchangeably. In this tutorial, we
refer to the output picture resolution of a computer screen as PPI. When we refer to the output picture resolution of a
machine such as an ink jet printer, the term DPI will be used. We will cover the technical differences of these terms in
more detail in another tutorial.
Image resolution is usually written as numbers such as 72 PPI, or 300 DPI. What that means is that in a particular image
file there will be 72 pixels (PPI) or 300 dots (DPI) within a one square inch area of the file. That will be 72 dots or 300
pixels from left to right and from top to bottom for each inch of the file. That information is important when it comes to how
your pictures will be displayed.
Computer screens are able to show clear and sharp images at low screen resolutions such as 72 PPI or 96 PPI. If you
take pictures that will be for on screen viewing only, you can set your camera to a low image quality setting such as one
megapixel or less. Taking pictures at high quality settings like 14 megapixels will not make the image look better on a 72
PPI screen. However, you will definitely need to set your camera to higher quality settings if your are going to make
enlarged prints of the pictures you take.
Calculating Maximum print sizes: As previously mentioned, to view pictures clearly on a computer monitor, the screen
only needs an output resolution of 72 PPI or 96 PPI. However, in order for a print to be sharp and clear, the output
resolution from the printer needs to be much higher. A printer output resolution from 140 DPI to 300 DPI is a better range
for making prints from your image files. (that is with 300 DPI being professional grade printing)
The photo enlargement chart shown above will gives the approximate maximum print sizes (in inches) to which you may
enlarge your pictures and retain good quality. Take note that the maximum sizes listed are guidelines and prints can be
enlarged to sizes slightly larger than those listed. However, a 3MP image that is enlarged to 16 x 20 size will be a very
poor quality print. Making prints smaller than the recommended maximum for the file size listed is not a problem. The
prints will still be very high quality.
The photo enlargement chart shows exact print sizes in inches. However, in reality those sizes are usually rounded off to
match the standard printing paper sizes available. Some of the more common print sizes are 4X6, 5X7, 8X10, 10X13,
11X14, and 16X20.
It is actually pretty easy to determine the maximum print size you can make from your digital images. First you need to
determine how many DPI (dots per inch) will be used when the file is being printed. To keep it simple, lets say the printer
output resolution will be 200 DPI. If your image file size is 2,000 X 1,600 you will be able to get a quality print size up to
about 10 X 8. The math involved in coming up with that size print is to simply divide the # of pixels in the width of the file
by the 200 DPI. (2,000/200=10). Next, divide the # of pixels in the height of the file by 200. (1600/200=8). So there you
have it. A file size of 2,000 pixels X 1600 pixels can be printed to make a good quality 10 X 8 photo when printed at 200
If you decide to make a print at 300DPI from the same image file, you will have a print with better resolution. However the
maximum size for a quality print will be smaller. Lets do the math.... 2,000/300=6.6. Next, 1,600/300=5.3. So if you round
the numbers out, the maximum standard size for that print will be about 5 X 7. Of course you won't have to do this type
calculation every time you take a picture. Just keep in mind that when you are planning to take pictures that will be
printed and enlarged, use one of your cameras' larger file size settings.