Board Thread:The Time Lord Academy/@comment-1432718-20131227055511/@comment-188432-20151112154708

Preview is only the most basic of editing programs. As the name suggests, it's mostly there on an out-of-the-box Mac so that when you click on a file ending in .jpg or .png, you'll get something to display on your screen. You can do some basic resizing, but that's not really compression.

I don't know what your budget is, but there are a ton of options for you. You can get "proper" Photoshop for about $10/month. Or you could buy Photoshop Elements outright. Though I'm not sure of the price for students, it goes for $99 retail. (You could almost certainly buy an older, cheaper version on Ebay if that's too steep for you.)

There are any number of apps in the App Store which will offer genuine compression, so many that it would be laborious to list them all here. Just to give you a ballpark, though, things like Compress cost about $5.

Or you could do any of a number of free online compressors, like the one I mentioned above, or the even-easier-to-remember http://www.resize-photos.com.