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Pictor Zoom series

Pictor Zoom series

Adjusting the back focus

Pictor Zoom series lenses will all go through flflange back test with

shims based on S35 standard before shipping, but flflange back distance

can vary on different cameras. If the flflange back distance is incorrect,

the camera will not focus at the correct distance.


1.To start with, prepare a Siemens Star chart, or other black-and-white

(high-contrast) resolution chart to test;

2.Attach your Pictor Zoom lens to the camera;

3.Rotate the iris to wide open;

4.Set up Siemens Star chart at 1.5M(4.9 Feet) away from the camera

(flflange), and make sure the target is in the image center.

A. Zoom in to the longest focal length, focus on the target until the target is

sharpest, and mark down the focus distance as S1.

B. Zoom out to the widest, focus on the target until the target is sharpest,

and mark down the focus distance as S2.

C.If the fifigure S2 < S1, increasing shim(s) is needed; If S2 >S1, then reduce

the shim(s).

D.Repeat step A to C until S2=S1. At this moment the lens is under Parfocal.