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Which Camera?
Which Resolution?
Which Lens?
Which Memory?
How to Edit
Use in PowerPoint
Printing

 

 

Resolution

Comparative Resolutions

  • Human eye                           about 120 million pixels
  • Colour TV (PAL)                    200,000 pixels (320 x 625)
  • 35mm transparency               about 20 million pixels
  • Digital cameras                     1.3 million and upward to around 12 million

In simple terms, this means image size and quality. All digital cameras have a resolution of 72 dpi (dots per inch, or the metric equivalent.) However, this is not a helpful 'real world' factor. Digital camera resolution is measured according to the number of photo image receptors, or pixels, used to record the image. Typically these will exceed one-million, referred to as Megapixels.

With one to two Megapixels cameras now mostly confined to camera phones, any new digital camera is likely to have a resolution of between three and twelve Megapixels, commonly five or six. The higher the number, the more image data is recorded and so the file size gets larger.

Guide to image sizes and ratios
Many cameras offer two or more image size options, which would allow many more smaller images to the taken and stored than larger ones. Unless you really don't wish to, always use the highest setting.

There is also the issue of image aspect ratio. The aspect ration is the horizontal to vertical ratio of the picture. With most cameras this will be fixed, but on some it is selectable. The most common is 4:3 which results in a picture the same shape as a standard TV or video image. Next there is 3:2 which is the same aspect ratio as a 35mm slide or negative; in other words is is more rectangular than 4:3. Professional and semi-professional cameras tend to use this format. Finally, there is 16:9, or wide screen; this is of little practical use for general photography. Remember the pictures as not getting wider, but less tall.

Illustration of image aspect ratios

The resolution also dictates the maximum recommended size at which an image can be printed without the individual pixels becoming noticeable. This requires a print resolution of 200 dpi or higher - roughly three-times that of the the original digital image. The table below gives a guide as the the approximate print sizes from a range of image sizes.

Typical Print Sizes (based on 4:3 ratio) at 200 dpi

Image resolution/size

Total pixels

Print size

6Mb (2816 x 2112)
5,947,392
36 x 27 cm
3Mb (2048 x 1536)
3,145,728
26 x 19.5 cm
2Mb (1600 x 1200)
1,920,000
20 x 15 cm
1Mb (1280 x 960)
1,228,800
16 x 12 cm

0.8Mb (1,024 x 768)

786,432

13 x 9.75 cm

0.3Mb (640 x 480)

307,200

8 x 6 cm

Updated:
24 May, 2006

© Nigel Sadler 1995-2008

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