Infinity focus is adjusted to 1/100th of a mm. Once you unscrew the lens (even if position is marked) infinity focus will be wrong when you reassemble (though depth of field will pull focus in). Was infinity focus correct when you took it apart? A focus collimator is needed to reset lens to proper infinity focus. John
it's quite easy to collimate for inifinity on a trip 35. just place a ground glass on film plane or scotch magic transparent tape and adjust the front element till it all comes into focus with the distance ring set for the mountains..