How to calibrate focus for MKX200 3.8mm fisheye lens

The depth of field of the lens was designed to be very deep at all aperture stops, so there is no need to tune the focus when shooting in the field. However, please make sure the focus is at peak in advance. The focus ring was retained by three tiny screws on the focal ring. If you moved the ring with force (such as during dismounting) or pointing the lenses upward during some vibrating journey there are chance of slipping and the image will become soft. Please follow the guide below to re-calibrate your lens:

1) Print several copies of this chart, preferably on A3 or better A2 size, it can be seen easier on a fisheye screen.

2) Set the charts at different distances to the lens, like at 1 meters, 3 meters and 6 meters. We want to have them clear at the same time. (fyi we used to check lenses in a room that is full of charts everywhere, you don’t have to print 30 copies, just 3 will be ok)

3) You may examine the live screen more easily by connecting the camera to a large 4K TV via HDMI, or connecting to an iPad with USB/Ethernet/Wifi and check with the Z camera app, you may zoom in by double clicking the area you want to check. If you do not have a big screen or iPad, you may check by taking a snapshot in JPG and check on your computer at full size.

4) Release the three tiny set screws on the focal ring of the lens with the hex key provided. Loosing a little will be ok, no need to take them out and do NOT lost them. If you have lost the hex key you may look for a replacement with a spec of M0.9 hex key.

5) Set the aperture to f/5.6 to start with, which has the peak performance by design. The center of the chart will look like a star shape when peak focus is reached. Please locate the best guess with all of the three charts are sharp, however there may be a range of “ok” peaking. You may further confirm the focus checking with f/4, then f/2.8. Adjust the exposure settings as needed for easy chart reading.

6) Lock the three set screws when you have located the sweet spot. 

7) Re-confirm the focus at infinity by shooting at some far away buildings and patterns, and then check a snapshot.

I believe you can do it with a little patience, let us know if you need further assistance, thanks.

p.s. the lens was not designed with frequent tuning and locking. The set screws may wear off if excessive force was used. The maximum torque would be at 300gf.cm.