As my aging eyes require a bit of help focusing (especially for nature shots) – I have found that the preset auto focus settings are NOT always reliable as released by the manufacturer for each camera body and lens.
To save me time, I put the following information together from several sources, the first section from: http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html and the second section from Spyder Lenscal.
Both Canon Micro Auto Focus and Nikon AF Fine Tune allow micro focus adjustments to calibrate a camera body to a specific set of lenses.
Here is my technique:
Firstly you can test your lens to see if it is properly calibrated already and does not need any further adjustment.
- Download the file www.jeffgardner.ca/ImagesJG/TestPattern/Testpattern.gif
- Using a calibrated monitor, display the above file in Photoshop at 100% (unscaled, exactly 100% on a screen and not on a print). You should see with your eyes the Moire interference Patterns.
- Place the camera and lens on a tripod so that its 100% parallel to the screen (for short lenses, a small mirror lying against the screen will display the front of the lens exactly). 50 times the focal length. For 50mm lens, 50*500=2.5m (25m for a 500mm lens, perhaps a laptop outside in this case). The test pattern should be symmetrical
- Using Live View – manually focus the lens on the computer monitor test image. Look for peek pattern visibility, not any particular pattern.
- Note the distance indicator on the lens carefully and the state of the image on the LiveView camera screen.
- Switch off LiveView and press the shutter button half way down to auto focus the lens. The lens should not move – the distance indicator should be identical to step 4.
- Reactivate LiveView – the image should be identical to step 4.
How to Calibrate the Auto Focus