In photography, understanding camera lenses helps you get creative control when shooting photos. Calibrating a lens is crucial to properly focus on your subject.
Professional photographers use single lens reflex (SLR) cameras. This type of camera comes in many varieties, manufacturers and models with a common denominator of being able to attach different kinds of lenses into the camera body. When using a Canon EOS 50D, you can do your own calibration to see if your lens is working well.
- Skill level:
Attach the lens that needs calibration to your Canon EOS 50D.
Open the camera and use the "Lens Micro Calibration" feature. Also called "Micro Adjustment" (MA), this is a camera-specific software command that adjusts the focusing value of a given lens, but it does not affect the lens itself. This allows each lens to lock the set-up calibration done through the camera's memory. This automatically compensates so that each lens is at nearly perfect focusing plane every time it is mounted into the camera.
Mount the camera on a tripod and set up a subject for the camera to focus on. Your reference target must have sufficient contrast so that the Autofocus (AF) system accurately detects it. Aside from being at the centre of your shot composition, it must be flat and parallel to the camera's focal plane. Make sure that the lighting is bright and even as well so that the image gets properly exposed.
Set the lens to "AF" and the camera to "One-Shot AF," and then manually select the centre focusing point as seen on the LCD screen. Choose the small rectangle found at the centre of the screen using the arrow selection in your camera that highlights specific options seen on the LCD screen. Set the lens to a maximum aperture (opening) by using "Manual" mode or "Aperture Priority" mode. Adjust the exposure level to have accurate exposure for your subject and use a low "ISO" setting. The low ISO setting requires ample light source to properly expose the image. Also, turn off the "Image Stabilizer" function.
Set the camera's self-timer before taking the shots or use a remote switch to avoid having to manually click the camera to take a shot. This prevents getting slight inaccuracies resulting from the hand's minimal movement when clicking the camera.
Take three sets of photos each using the following micro adjustment settings: "-5," "0" and "+5." You will acquire a total of nine images. You may actually take additional sets of test images using different micro adjustment settings so you have more options to compare which shot has the sharpest image.
Go to the "Play" mode of the camera to view the photos you shot and look at each image on the LCD screen at 100 per cent magnification.
Register the micro adjustment settings of the camera based on the sharpest image shown on the test shots. This sets the particular lens with the right calibration settings for the camera.
Tips and warnings
- Telephoto lenses have a greater effect on even small micro adjustment settings. With wide-angle lenses, it is the opposite.
- When setting the micro adjustment settings for a zoom lens, the setting can only be accurate for the focal length setting used during the test. When using a zoom lens, it is highly recommended to test either at the longest focal length or the focal length you use most often.
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