Preparing photos and other graphics
Graphic sizes on the screen are measured in pixels - the actual dots which make up the screen display. If you are starting with a digital camera image, it will almost certainly be far too big, but that's OK. If you are scanning a print or transparency, it's a good idea to start with a scan that's too big, too.
You don't have to use the whole photograph - you may want some part of it which may not even be the main subject.
Crop your photo so you have just the part you want;
Carry out any processing you want e.g. adjusting brightness, contrast;
Resample the picture down to the size you want: a full width photo in a modern design could be up to 2000 pixels wide, but typically, images will usually be quite a bit smaller. I'm inclined to think that 800 pixels wide is reasonable for a photo gallery, for example. A modern digital camera produces massive images, and you don't want people to be waiting for that kind of picture to load when they visit your page. Set a sensible dpi value so you have some kind of consistency when pages are printed (96dpi is good, or 72 if you're an Apple user).
The three main formats for graphics are JPEG (JPG), GIF and PNG. PNG was created as a replacement for the GIF format, has steadily gained popularity, and is now widespread.
The standard rule of thumb for choosing which format to use is to save anything which is photographic in appearance as a JPEG file, and anything that's more cartoonish - with large blocks of just a few colours - in PNG (or GIF) format. See what looks best and what makes the smallest files sizes.
Adding graphics to your website
Whatever kind of system you are using for maintaining your website content, you should at least be offered the option of adding an alternate text description ('ALT text'). You should describe the image for the benefit of someone who, for whatever reason, is viewing your page without seeing the image. (So don't just repeat any caption you have given.)
Remember that the alternate text is available to all, so don't e.g. for a photo of children, include the names you have carefully omitted from the caption.
Last updated: April 2017