TECHNICAL INFORMATION

The numbers in the concentric and linear targets, in twentieth of a millimeter, express the distance between the two axis by two black (or white) consecutive lines.

USER MODE OF THE MIRROR CENTERING AID :

Place the chart parallel to the image plane using the magnetic mirror on the center of the chart.

1. Place the magnetic mirror on the center of the chart by using the 4 discreet magnets.
2. Place the camera at the rough required distance from the chart.
3. Move the camera legs, pan and tilt to film the center of the lens mirror relection.
4. Doing this, the optical axis becomes perfectly perpendicular to the chart. Because you film the center of the chart, the sensor is equidistant about its 4 corners.
5. Finally, adjust precisely the distance using the sliding plate.

USER MODE OF THE CORRELATION TABLE :

The correlation table gives you the correlation between the numbers in the concentric and linear targets, the number of pairs of lines printed on the chart on 1 millimeter and the number of pairs of lines printed on the film or sensor on 1 millimeter.

To use this correlation table, place the chart at a distance from the image plane 50 times the focal lengh of the lens to be tested (in either millimeters or inches).

Example for a 50 mm lens :

50 x 50 = 2500 mm = 2,5 meters = 8 feet

Analyse your lenses and print them with stop wide open.

The degree of sharpness depends on the clarity between the lines. The resolving power depends on the number of lines seen.

Find the optical wedge sheet corresponding to the lens on test.

Write the informations about the lens on test in the corresponding areas : brand, serial number, focal, stop.

Place the camera from the P.A.T. chart at the distance advocated by the optical wedge sheet (approximately 50 times the focal lengh of the lens).

4/ Stick the center of a self-adhesive graph paper on the engraving fixed mark of the lens.

a/ Write in the «Ratio» area the ratio corresponding to the lens. The ratio depends on the gap between focus engravings. It has to be multiplied with the measurement unit of the scale (mm).

b/ Millimeter is the measurement unit of the scale. It goes from -5 mm to + 5 mm and corresponds to the variation of the lens ring in the minus or in the plus directions around the correct testing distance of the lens.

For exemple : if the ratio is 3, then -5 mm becomes -15 mm, -4 becomes -12 mm, -3 mm becomes -9 mm, etc.

Write in the «eye» area (useful for camera films to calibrate the viewfinder) the best focus reading.

Record or print a few frames of each variation of the lens ring, using the ratio multiplied with the mm, from the minus to the plus.

With digital cameras, play your recording and find easily the best result.

With film cameras, analyse the picture frames with a microscope to find the best result.