If you ever wanted to know how to upgrade your iMac's ram here's how. When it comes to ram there are multiple places you can buy from. However, buying ram from Apple is like buying your tires from a dealership. Buying third party ram is a better option and can save you some money. OWC is a great resource to buy many products. In the world of photography having more ram is very useful when it comes to multitasking. These videos show you how to upgrade ram on Apple's 2011 iMac model as well as upgrading the ram on their newer 2012/2013 iMac.
Here's a link to the article that Gary Martin wrote for Fstoppers.