M240 focusing

[tardegard]

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Hi guys, 
I have had an M9 for long time with no issues. 
Time ago I passed to M240 which I really love as it seems a true improvement. 
I noticed though some weird difference between the two cameras regarding focus and mostly infinite focus. 
When I had to shoot some very far away object with M9 (say 4 km) I used to set the focus ring just a very little bit before the infinite hard stop. I seem to remember that with M9 I never got all the way down to actual infinite mark, even when I shot the stars maybe. With M240 it seems pretty different. I never use live view with it (don't like it), but it seems to me that if I have to focus on a 4 km distant object now I need to set the focus ring on the actual infinite mark in order to have the image perfectly sharp (with Elmarti 90mm at 2.8). The range finder patch seems calibrated (patches are even) at this distance (4 km) but it seems not very much so if I shoot some objects al little bit closer, say 500 meters. 
No issues at all with closer objects like few meters (10, 20 or so). 
Does it mean that my range finder needs to calibrated? 
is it something I can try and do by myself? any guide?

[sinjun]

From what I understand you to say, it seems as though the M240's rangefinder is well calibrated and you M9's was not. At infinity the images should line up in the patch as you hit the lens hard stop (assuming the lens is not out of adjustment). 4 km is probably far enough away for a test though a bright star or moon is better. The main thing is that closer objects (20 metres and below) are in focus on patch alignment since depth of field will normally cover for possible miscalibration at longer distances.

[tardegard]

17 minutes ago, sinjun said:

From what I understand you to say, it seems as though the M240's rangefinder is well calibrated and you M9's was not. At infinity the images should line up in the patch as you hit the lens hard stop (assuming the lens is not out of adjustment). 4 km is probably far enough away for a test though a bright star or moon is better. The main thing is that closer objects (20 metres and below) are in focus on patch alignment since depth of field will normally cover for possible miscalibration at longer distances.

Thank you Sinju, I try to make it a bit clearer: 

objects at 100/200 meters (not infinity) line up when I hit the hard stop (infinity), and the shot fo these objects is obviously not sharp: in fact I need to focus a bit closer in order to have it sharp. 

[sinjun]

Oh OK. If the rangefinder calibration also makes it back focus at closer distances (i.e. if you focus on something at 5 m and really the point of focus in the image is behind, say 6 m) then you might be able to correct by adjusting the infinity setting as in link below. Often miscalibration can be fixed like this. However, if there is no issue at closer distances then it also requires a more difficult concurrent change to the rangefinder roller arm which I personally wouldn't try myself, though others have with some success.