Re-shimming procedure for Astronomik FULL SPECTRUM MOD only:

The Astronomik MC clear glass filter by itself does not correct the camera's Auto Focus function. This is because the thickness of the two filters removed from the camera's body during the modification (LPF#1 and LPF#2) is not equal to the thickness of the Astronomik MC clear glass replacement filter. Small shims are used by Canon to adjust for precise focus of the CMOS imaging chip assembly and also to correct its tilt in the non-modified DSLR body. Canon may use one, two or three shims of varying thickness on each of the three CMOS imaging chip mounting screws. All of the shims at each of the three mounting positions need to be noted and measured using a digital micrometer. The digital micrometer used should be accurate to + or - 0.02mm.

Here is an example of shim thicknesses found in one camera:

Position 1	.35mm shim and .05mm shim
Position 2	.35mm shim and .10mm shim
Position 3	.35mm shim

In the above example you can see that a .35mm shim is used at all three positions and this is to correct focus. A .05mm and a .10mm shim are used by Canon to correct the tilt of the CMOS imaging chip assembly. The shims used to correct tilt by Canon, in this example the .05mm and .10mm shims, will be reused at the same positions in the modified camera. The shims for focus, .35mm thick in this example, will need to be removed and replaced with shims of a different thickness to correct the Auto Focus function of the modified camera. You will need to measure the thickness of LPF#1 and LPF#2 filters for the following calculation because they vary between camera models.

• Original Canon LPF#1 and LPF#2 combined thickness: 1.40mm
• Replacement Astronomik MC clear glass thickness: 0.97mm
• Difference is .43mm
• The out of focus distance = (n-1)/n X Difference where n is the refractive index (1.517 for glass).
• The out of focus distance = (1.517-1)/1.517 X .43mm = .147mm
• So the out of focus distance of .147mm is the distance the CMOS imaging chip needs to be moved toward the lens.

This can be done by reducing the .35mm shims by .147mm.

• .35mm minus .147mm = .203mm

At auto supply stores, feeler guages are sold as sets in various sizes and many include a feeler guage that is .203mm (.008") in the thickness needed for this example. Cut the three spacers out of the .203mm feeler guage to a size of about 4mm by 4mm. Drill a hole in the center of each shim with a 5/64" bit, large enough for the CMOS assembly mounting screws to fit through. It may be easier to drill the holes in the feeler guage before cutting it to the shim sizes.

The three .203mm thick shims that have been made, replace the three original .35mm thick shims used to correct focus. The shims used to correct tilt (.05mm and .10mm in this example) also need to be added to their original positions.

With these shims in place, you can now Continue With The Modification Procedure.