History 402A (Dr. Cawthra): Working with Items & Collections on Omeka.net

Learn how to add, edit, describe, and display Items and Collections.

When selecting digital images to include in your Omeka mapping project– whether photos, illustrations, graphics, maps, image copies of documents, etc. – there are several image properties you want to take into consideration.

• Image File Format: For image content displayed on the web, you generally want to use a .jpg file for photos and .png files for graphics, but either file format will work well for digital exhibits.
• Image File Size: Try to download images or resize the images at about 300 KB maximum. This is so that the images you use in your Omeka project do not fill up your storage quota. Free Omeka.net accounts get 500 MB of storage. This is also to help your exhibit web pages load faster. Large image file sizes take longer to load.
• Image File Dimensions: Understanding how to read an image file's dimensions can help you select images that display the best in your digital project. You want to select and upload an image that is large enough for your project visitors to see well. Image file dimensions on the web are displayed in pixels, as width x height. If image dimensions read as 700 x 400, we interpret that as 700 pixels wide by 400 pixels high. For Omeka projects, I generally recommend selecting an image dimension that is at least 300 x 300. Based on how much Omeka.net free themes are designed, I usually prefer an image that has a width of about 700 - 900 pixels wide or 700 - 900 pixels hight. Those "maximum" pixel dimensions tend to display well in the item records that you create, filling up extra white space.

The above example is a photo item record from Wikimedia Commons, for a Creative Commons-licensed photo of Yosemite National Park. Underneath the image preview box, we can choose to preview and/or download that photo in multiple image file dimensions. For an Omeka project, I would probably select the 884 x 760 option or the 552 x 480 option. The 1,178 x 1,024 and the original file size of 2,000 x 1,738 will be larger file sizes, and they will consume more of your free storage space. If you were using this photo in a print panel for a physical exhibit, you would want to choose the largest file size with the highest resolution since that will look best on print materials.

Learning Activity: Visit that Wikimedia Commons item record and click on each set of image file dimensions to gain a better understanding of how each of those those photos look in your web browser.

Embedding Videos

While Omeka.net allows you to upload an actual video file, that method eats up a big amount of storage space. An alternative is to embed video from video sharing sites like YouTube and Vimeo.

Embed YouTube Videos & Playlists (2016)

This video from YouTube Help walks you through how to embed videos or playlists on to a website or blog.