In my last article I discussed image rights. This time we will talk about the technical aspects of pictures such as size, resolutions and format.
Size and Resolution
First of all images have dimensions, meaning width and height.
I know this is hardly a newsflash. However, dimensions are either indicated in pixel, in millimetre or in inch. In the world of Web you will typically see the number of pixels plus the indication of a “measurable” size. The larger the image dimensions the larger the file in respect of kilobytes.
But there is also a second very important factor: the resolution. If you want to print an image you will look for a resolution of 300 dpi to receive a good quality. This means that one square inch is covered with 300 pixel (or dots if you print it).
For a web image you should only use images with a resolution of 72 dpi. There are two reasons for this:
On a browser you will see no difference in the quality since it works with 72 dpi.
Let’s say you have an image of a width of 7 x 5 inch. If your image has a resolution of 300 dpi the total amount of pixels will be 10500. If the same image has only 72 dpi it contains 2520 pixels which is more than 4 times less. Needless to say that it loads a lot faster.
You might say that we all have fast internet connections and that this is not important. You are right, for one image of the above size it does not matter. But did you notice how many websites and blogs have huge wallpapers? Trust me it does make a difference.
Working on Images
Let’s say you want to insert an image in your blogpost but the dimensions are too large. Of course you can use the mouse and make it smaller. It will LOOK smaller but still be as heavy as before. The reason is that you only pushed the pixels closer together. Again, if you have just one small image there is no problem. But if you insert many graphics or large ones you will experience a longer loading time.
That is why you need a graphic programme. If you open an image with such a tool and save it with smaller dimensions it will automatically reduce the number of pixels and the image “weight” in respect of megabytes along with it. But do not try to enlarge it because poor raw material will not bring satisfactory results. Unless it is a vector graphic (see below) the only thing that happens is that the pixels become bigger and your image will be blurred.
The professional graphic programmes are very expensive. Therefore you might want to try GIMP which is available for Mac and for PC.
If you download pictures from one of the image portals I mentioned in my previous article they will normally be available in different sizes and resolutions. So you choose according to your needs.
The format will be jpg or jpeg. This is very suitable for web and printing since it compressed and still offers a wide colour spectrum. Your smart phone images will have the same format.
If you need a transparent background or a shape like i.e. a circle you want to work with png. Technically, the image is still square (there are no other images on the web) but everything outside of the circle is transparent. If you are familiar with a graphic programme you can cut the object or the part of the image you want and place it on a transparent background.
Portals offer so called vector graphics. This are images which can be seamlessly enlarged to more or less any size and still keep their high quality. The typical format is eps which can only be read by professional graphic programmes.
I never needed one for web or blogging neither probably will you.
I try to avoid the formats bmp and gif. The first one because it is too heavy (in kilobytes) and the other one because it has a much reduced colour spectrum which makes the images look “gritty”. But if you only use black and white or want a transparent background a gif-images might come in handy. It is very small and therefore loads quickly.
You will find your own style and the image size and formats that suit you best. And of course the content is still important and the image should illustrate it.
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Next post on images: Branding