Find a subject with a contrasting pattern (like upholstery, carpet, or even a print). 2. Put your camera on a tripod. 3. Set your camera to aperture priority mode. 4. Start at the widest aperture of your lens, set the focus point on the pattern, focus, and take the shot. 5. Then select the next aperture and without changing the focus point, refocus, and take the shot. 6. Repeat this until you’ve taken images at every aperture of your lens. 7. Import the images to your photo editing software. 8. View the images at 1:1 and compare sharpness between the images to find the aperture with the best sharpness at the point you set the focus point.