We photographers often discuss the merits and pitfalls of particular lenses, and one important area that we expect to be ‘dead-on’ is focus accuracy. However, even the finest optics are not always calibrated with 100% accuracy from the factory, but if you’re shooting on a high-end body, you can take matters into your own hands to get the sharpest possible shots.
Different manufacturers use different titles for their menu setting to adjust micro focus – Canon and Sony call theirs ‘AF Micro Adjustment’ while Nikon’s is labeled ‘AF Fine Tuning.’ If your body has this setting, you can use a calibration device to get perfect focus with your individual lenses. David Patiño of the excellent industry publication, PDN, has released a video on YouTube walking photographers through the process.
First, you will need a calibration device. The one used in the video is a SpyderLensCal device, but there are others available or you could even make your own.
When setting up to make micro adjustments to your focus, there are some steps you will want to take to ensure the best results. First, set your camera to its lowest ISO for the cleanest possible images. You will be visually examining the images to make your adjustments and this will help you see sharpness clearly.
Put your camera on a sturdy support of some kind, like a tripod or camera stand at a distance from the calibration tool of 20 to 50 times your focal length. Use mirror lockup to avoid any camera shake, and trigger your camera remotely. Shooting tethered is the best way to easily look at the small details while you work so you can see what adjustments need to be made.
Once you’re set up, align your camera’s center focus point with the area pictured above (inside the red square) and focus your camera there.
Using the ruler on the right, examine the image via your tethered computer to see which numbers are sharpest. Ideally, ‘zero’ will be sharp and the numbers in front of and behind the target will fall out of focus at an equal rate. In the example shown in the video, this is not the case, however, providing an opportunity to demonstrate the process.
In David’s Canon 5Ds AF Fine Tuning setting, he makes the appropriate adjustment and achieves proper focus so you can see exactly what to do if you are shooting Canon, or a guideline for the same process with other brands. If you are having focus issues or just want to see if your lenses are meeting their full potential for sharpness, we highly recommend you watch this short video demonstration and acquire a calibration device.