Deciding what size image to buy or if the image you have will print properly and fill the space required can be a crucial problem! Trying to use an image as a full page spread will only work successfully if big enough and knowing how big it is is often left to trial and error! In the previous article resolution was discussed and how big images can appear in different resolutions required for print versus those needed for the web.
The guide below shows you the size in mm of the image, the size of the image in ‘kb’ or ‘mb’ at both 72 dpi and 300 dpi.
This should help you when considering how big an image needs to be for the purpose you require.
300 dpi – 80 x 80 mm/945 x 945 px = 1.2 mb
72 dpi – 80 x 80 mm/227 x 227 px = 138 kb
72 dpi –
100 x 100 mm/283 x 283 px = 165 kb
Getting a 72 dpi image when you need 300 dpi has quite severe consequences, stretching and enlarging it will fill the gap but the quality of the image will be severely effected.
So a 10mm image is 118 px square at 300 dpi making 109 kb multiplying that by 10, the 100mm image is 1181 px square.
Using these dimensions you should be able to multiply up to the rough size you will need for either 300 or 72 dpi.
You will also be able to refer back to compare the size of image you have and how big it is likely to be.
When searching in stock photo sites the image sizes are given in both pixels and mm and will state the resolution. When searching Google for images the sizes are always given in pixels, its very rare to be at 300dpi but you will have to check.
The first screen shot is from a Google image search, its a large image measuring 36.12 x 27.09 cms at 663 kb. You can set the search criteria to show the sizes of the images or just which sort of size you are looking for. This also reduces time and disappointment when searching for pictures that you like but find they are too small to use.
Have you seen any terrible examples of images that have been used at too small a resolution and have been stretched to extremes?