Master lens for 054 finder back adjustment (054-5202-79)

The Minolta master lens for finder back adjustment is basicly a MC Rokkor-PG 50/1.4 without diaphragm and aperture ring. It has a special focusing mechanism, which allows focusing around infinity in a very small range. Its prupose is to figure out, if the focussing screen is in the correct position.

Since it has not the usual focussing range, the distance scale numbers are not painted, just the infinity index is marked. The lens has a special highly precise machined bayonet mount. Note the lack of the pre-set pin.

The white mark indicates a distance of exactly 43.58 mm between the bayonet flange and the image plane for infinity. Using a collimeter, a target is focused watching the split screen in the view finder. The colored lines represent a change of a 1/100 mm in flange back, so one can determine a misalignement directly. A service technician has attached a sticker with the marking for the X-700.

With X-1 and XE cameras, the finder back distance has to be 43.58 mm 0.02 mm. This is represented by the first two yellow lines besides the white line. With the X-700, the default value is 43.565 mm 0.02 mm.

The bayonet flange seems to be made of a hardened steel, to prevent any abrasion and keep the exact flange distance.

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