The Megapixel Dilemma

Information > The Megapixel Dilemma
27/09/2011 - 17:31

 

Image quality is partly determined by how many pixels you have in your print, so to achieve true photo quality you will need a maximum of 300 pixels in every inch of your print (300 ppi) both horizontally and vertically, whilst for web or projection 72ppi or 100ppi is satisfactory.  The difference is that a printer needs to use more pixels per inch to produce a high-quality image than your monitor does - in this explanation we will not discuss dpi – info is available on the web and in books.

 

For home / club use you can print at 250 or even 220ppi for a photo to look more like a print made by a professional service.  Generally more pixels per inch = higher quality printed photograph.

 

 

Notice that as the print size doubles, the megapixels required increases geometrically. The table below shows the maximum print sizes that can be achieved for a given sensor without interpolation.

 

 

  • A typical 10 megapixel camera produces images that are 3872 x 2592*  pixels.  If you multiply 3872 by 2592, you get 10,036,224 or 10 million pixels.

 

  • To find the largest photo quality image you can print, simply divide each dimension by 300: 3872 / 300 = 12.9 inches       2592 / 300 = 8.64 inches

 

  • If you are not entering your images into an external competition or magazine, you can reduce the resolution to 250ppi or even 200ppi.  Most inkjet printers can produce a quality print at 250 or 200ppi.  

 

  • Be aware that image editing software like Photoshop interpolates between pixels so that you can print larger, so it may not be obvious that quality is being compromised!

 

 

 

Print Size Chart

Megapixels

Pixel Resolution*

Print Size @

300ppi

Print size @ 250ppi**

Print size @ 200ppi***

6

3008 x 2000

10.0" x 6.7"

12.0" x 8.00"

15.0" x 10.0"

8

3264 x 2448

10.8" x 8.2"

13.1" x 9.8"

16.3" x 12.2"

10

3872 x 2592

12.9" x 8.6"

15.5" x 10.4"**

19.4" x 13.0"

12

4290 x 2800

14.3" x 9.3"

17.2" x 11.2"

21.5" x 14.0"

16

4992 x 3328

16.4" x 11.1"

20.0" x 13.3"

25.0" x 16.6"

18

5184 x 3456

17.3" x 11.5"

20.7" x 13.8"

25.9" x 17.3"

  

            * Approximate Resolution.  Actual pixel dimensions vary from camera to camera.

**At 250ppi, good image programs can carry out some pixel interpolation and print at
       A3 without appreciable losses.

*** At 200 ppi losses may be seen due to interpolation and picture may lose sharpness
      and appear fuzzy, depends on picture type, printer and contrast etc.

 

Note approx. sizes:   A4   = 11.7"x  8.2",    A3   = 16.5"x  11.7"       A3+ =    19"x  13.0"