Adjusting the Viewfinder Focus on Your Canon EOS Rebel T3/1100D
Located on the top-right edge of your Canon EOS Rebel T3/1100D, the viewfinder is a tiny black knob, labeled in the following figure. Officially known as a dioptric adjustment control, this knob enables you to adjust the magnification of the viewfinder to mesh with your eyesight.
Adjusting the viewfinder to your eyesight is critical: If you don't, scenes that appear out of focus through the viewfinder may actually be sharply focused through the lens, and vice versa.
Follow these steps to adjust your viewfinder:
Remove the lens cap from the front of the lens.
Look through the viewfinder, aim the lens at a plain surface (such as a white wall), and concentrate on the focusing screen shown on the right side of the preceding figure.
The focusing screen is the collective name assigned to the group of nine autofocus points that appears in the viewfinder — the little squares with the dots inside. One of the little guys is labeled in the preceding figure.
Rotate the dioptric adjustment knob until the autofocus points appear to be in focus.
Don't worry about focusing the actual picture now; just pay attention to the sharpness of the autofocus points.
If your eyesight is such that you can't get the autofocus points to appear sharp by using the dioptric adjustment knob, you can buy an additional eyepiece adapter. This accessory, which you pop onto the eyepiece, enables further adjustment of the viewfinder display. Prices range from about $15–$30 depending on the magnification you need. Look for an E-series dioptric adjustment lens adapter.