Adjusting Your Camera's Viewfinder

To make sure I had this in focus,
I needed to make sure my viewfinder's diopter was set properly

Not all photographer's eyes see and focus the same way; some are farsighted and some are nearsighted.  This can seriously affect your ability to see that your image is sharp in the viewfinder.  And it's hard to see through a viewfinder with glasses on.  Thankfully, the fine makers of digital cameras have included a diopter adjustment on most DSLRs that allow you to account for this.

On most cameras, the adjustment dial is near the viewfinder; in some cases, it may be necessary to remove the rubber guard from the eyepiece.  If you haven't done that before, don't worry.  It's easy to get it on and off.  Check your camera manual to locate the diopter adjustment dial for your viewfinder.  Once you locate the dial, look through the viewfinder and autofocus on something nice and sharp.  Then adjust the dial until the focus points and the text displaying the camera settings in the viewfinder are nice, crisp and sharp.  Confirm this by checking to make sure that the subject you have auto-focused looks sharp.  I find it easiest to put my camera on a tripod to do this.  Once your diopter is set properly, you won't have to change it again unless your vision changes or the dial gets turned accidentally.  This adjustment will not correct for every vision issue, but it will at least get you in the right direction