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A Simple Explanation About Resolution

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Have you ever heard?: “Your photos aren’t good enough” or “the photos you gave me are too low resolution” or even more confusing “I can’t use the photos you gave me in the size you gave them to me in”

I admit it; that is confusing and here’s what you need to know about photos and resolution for your website or brochure or any advertising related item:

Have you ever seen a newspaper that’s had a misprint and you can see some red or yellow dots off to the side?  Those are the dots that make up any and all illustrations and photos; those are the dots that artists are referring to when they talk about “Dots per inch”.  Photos are made up of dots (there are other names, but for this basic intro, dots will suffice).  Dots per inch imageA photo’s resolution is expressed by the number of “dots per inch” or “DPI”. Low resolution photos have fewer dots per inch and high resolution images have more dots per inch. Some applications require images with fewer dots or lower resolution images (websites, for example only need 72 dots per inch) and some uses require more dots or higher resolution images (magazines or brochures printed with “Offset” printing, for example, need 300 or more dots per inch).

So just imagine that you have a photo that is made up of a whole bunch of dots – let’s just say there are 150 dots in every inch of that photo.  Now let’s also say the physical size of the photo is 2″ x 2″ (i.e. what is the photo’s size if you measured it with a ruler?).  Now let’s say you need that 2″ x 2″ photo to be twice as big – so you increase or double it’s physical size to 4″ x 4″. When you double the size of an image, you are stretching those dots out so they are further apart, thus REDUCING THE NUMBER OF DOTS PER INCH.  So when your graphic designer or web programmer tells you your image can’t be made any bigger, this is why – becuase when you make an image bigger you are automatically stretching the dots further apart or increasing the space between the dots and by doing so you are reducing the number of dots per Resolutioninch (or decreasing the resolution).

At the same time if you REDUCE the size of your photo from 2″ x 2″ to 1″ x 1″ you are pushing the dots closer together – so you are increasing the number of dots per inch, thus increasing the resolution.  So sooner or later you might hear someone say “we can make this image smaller but we can’t make it bigger”, and that is why.

What can I take away from this article?

Image Resolution Rules

You need a different resolution photo for each use, from Websites to Brochures to InkJet print outs, as follows:

  1. Website Images – can be 72 dpi (you CAN use a higher resolution image or an image with more dots, but as you increase the resolution of the image on a website you are also increasing the time it takes to download on to the website, so it’s better to stick with lower resolution images for the Internet.
  2. InkJet Printed Images – need to be 150 dpi
  3. Offset Printed Images – need to be 300 dpi or higher  (offset printed images are professionally printed items like brochures or magazines).

Don’t forget, if someone gives you an image that’s 72 dpi to use on a website, and you need it to be twice as big as it currently is, you won’t be able to use it becuase as you increase the physical size of the photo, you will reduce the number of dots per inch (the resolution).  If you are asking someone for a photo, try to always ask them for the best photo, in the highest resolution, that they have.  It’s much easier to get what you need from a high resolution image, than it is to get what you need from a low resolution image. This is just a very basic introduction to the subject of image resolution but at least you can begin to understand what all the talk is about image resolution and dots per inch!  If you have any questions I’m more than glad to help you; just shoot me an email at emily@mdept.com.

 



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