The PICTOR ZOOM zoom lenses have been calibrated to the standard S35 flange focal distance at the factory. However, the flange focal distance of different S35 cameras may vary slightly. To facilitate compatibility with different cameras and achieve the best imaging results, you can adjust the back focus.

Please follow the steps below for the adjustment process.

1. Prepare the subject. You can use a "Star Chart" or other black-and-white, high-contrast subjects;

2. Install the lens onto the camera;
3. Select the maximum aperture;
4. Place the subject approximately 1.5m away from the camera's sensor plane, with the subject positioned in the center of the frame;

Instructions for PICTOR ZOOM Back Focus Shim Adjustment
Adjustment Operation:
A: Rotate the zoom ring to the longest focal length end, then rotate the focus ring until the image is at its sharpest, and record the focus scale value S1;
B: Rotate the zoom ring to the widest focal length end, then rotate the focus ring until the image is at its sharpest, and record the focus scale value S2;
C: Compare the values of S2 and S1. If S2 is smaller than S1, you need to add back focus shims; if S2 is larger than S1, you need to reduce back focus shims; (The adjustment amount of the shims is related to the rotation angle of the focus ring corresponding to the difference between S1 and S2. The greater the rotation angle, the more shims need to be adjusted, and vice versa)

D: Repeat steps A and B until S2 equals S1, which indicates that the lens is in a parfocal state and the adjustment is complete;

Example: Taking the Pictor Zoom 50-125 as an example, suppose the lens zooms to the 125mm end, and when focused until the image is sharpest, the focus scale value is 1.5m. Then zoom the lens to the 50mm end and refocus until the image is sharpest; at this point, the focus scale value is 1.4m, which is smaller than 1.5m. According to experience, after adding 0.1 of a back focus shim, reconfirm. At both the 125mm and 50mm ends, the focus scale value is 1.5m when the image is sharpest, indicating that the lens is in a parfocal state and the adjustment is complete;