Tag Archives: kilobytes
Requesting images – Things you should know!
While everyone has a camera and a computer, not everyone knows what is required to get images into print. Below are the main components that you need to know.
1. Resolution relates to the number of pixels that go to make up the image file and is measured in dots per inch (dpi). The higher the dpi, the higher the image quality.
2. ‘High Res’ generally means a resolution of 300dpi or greater, suitable for offset printing, brochures, photos and large wall prints. But this does not tell you the dimensions of the image.
3. ‘Low Res’ generally means a resolution of 72dpi, only suitable for the web and previewing. But again this does not tell you the dimensions of the image.
4. Image size refers to the actual dimensions of the image at a set resolution. eg A4 hi Res is 29.7 x 21cm @ 300dpi A4 Low res is 29.7 x 21cm @ 72dpi
5. File size is measured in kilobytes (kb) or megabytes (mb). But the file size does not tell you the dimensions or resolution of an image. (see image size)
6. File compression vs Open image file. As an example a 25mb Image file (photo) opened in your favorite image editor can be saved as the following file sized jpegs 5.8mb, 2.5mb, 1.4mb and 736kb. Size depends on the Jpeg compression used, the more compression the lesser the quality.
7. When requesting a digital image, you should know what the file is to be used for!
a) What size do you want the final image to be? eg A4, A3, wall size.
b) How is the image to be used? Will it be a photographic print, in a brochure or on a website? (This tells us the resolution and colourspace required)
c) What file format required – Jpeg, Tiff, EPS, PDF. Ask for Jpeg unless otherwise instructed.
Feel free to contact us for more information.
‘Image size’ , File Size and ‘Resolution’
‘Image size’ , File Size and ‘Resolution’ are three terms that are often and easily confused.
Image size is measured in kilobytes (kb) or megabytes (mb) and is relevant to the open uncompressed image.
• Compressed file size – using compression algorithms various file formats reduce file size of the image file. Some keep the quality of the image (Lossless) others, loose information as a compromise for file size (Lossy). See the ‘Image file formats’ article in this blog for more information.
• Uncompressed or open file size – This is the actual size that the image comprises of when open in a program like photoshop.
File size is measured in kilobytes (kb) or megabytes (mb) and is relevant to the the saved file size of an image. This size depends on what if any compression is used. See the below table showing the varying file sizes and compressions used.
Based on a A4 image open in photoshop which is 24.9mb
File format Compression File Size mb Quality Jpeg 12 5.8 mb excellent Jpeg 10 2.5 mb excellent Jpeg 8 1.4 mb good – excellent Jpeg 6 1.1 mb average Jpeg 4 736 kb poor Jpeg 2 564 kb rubbish TIFF nil 25 mb excellent TIFF LZW 13.1 mb excellent TIFF Zip 11.5 mb good – excellent
See the ‘Image file formats’ article in this blog for more information.
Resolution is measured in dots per inch (dpi).
An A4 300dpi RGB file is 24.9mb and can be reproduced in any number of dimensions relevant to the different resolutions used.
Resolution Width Height 300dpi 21cm x 30cm 150dpi 42cm x 60cm 75dpi 84cm x 120cm
