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M4-P RF Calibration - how important with your own lens ?


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Hi,

 

I recently got an M4-P, and I suspect its RF patch is a bit out of whack, and needs calibrating.

For example, at infinity the patches never line up, at 0.6 and 0.7 on the 35 mm Summilux-M ASPH FLE it seems a little out, with the difference getting bigger the further away I go.

 

I just gave  a test film to my local camera shop in Nantes to get developed, and they recommended a company in Paris who could re-calibrate the RF. I phoned them, and they can re-calibrate the RF patch for me. They're happy to receive the camera by post. They said to include the lens (I use more than one lens anyway), but I'd rather just send the camera and ask them to use one of their lenses.

 

So my question is how important is it to have the RF calibration done with your own lenses ?

 

And furthermore, if you have more than one lens, surely if the calibration is done one one lens it's optimised for that particular lens and not the others ?

 

Rob

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Hi Rob, from your description it looks like your infinity setting on your M4-P is not correct.

Both the camera and your lenses are set against a calibrated standard. So you don't need a lens to adjust the focus of your camera

 

The camera setting for infinity is the large screw situated in the roller that runs against your lens when you focus.

The screw can be reached with an angled screwdriver when you have removed the lens. You might need to adjust the size of the screwdriver with a metal-file.

You turn the screw, mount a lens and check if the RF patches coincide at infinity. Tweak until okay.

 

With a little luck it's only the infinity setting and you can be done in a few minutes.

In difficult cases the near-by setting is now off. In that case your camera is best serviced by a professional.

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Hey Maarten,

 

Thanks for this information.

I'll know in about 10 days (when the B&W film is back) whether the RF is off at the short distances.

From some crude tests done today, positioning the camera at fixed distances away from a target to focus on, I get the impression it's also off at the shorter distances. However, maybe correcting at infinity will 'move in' the shorter distances so they are correct ?

 

If I do have to send off to a professional, I prefer to only send the camera. This shouldn't be a problem, should it ?

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I confirm there is no need to send the camera to have it RF adjusted.

This is the tool I mentioned. Skania is one of the manufacturers and not expensive.

Adjusting infinity focus is really easy when you know how to operate a screwdriver.

 

 

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Just a quick update. I rotated the screw on the large cam a little bit (anti-clockwise) and the inifity extreme with my 35 mm Summilux-M ASPH FLE and 35 mm and 50 mm Summilux-M ASP APO seem pretty much spot on. Then for both these lenses I focused a at known distances on a target (XQ-1 logo on a Fuji compact camera) at the short end (70 cm, 80 cm, 90 cm, and 100 cm), and they seem good.

 

I then put my 90 mm Tele-Elmarit on, and it seems a slight bit out at the short end (near) distances. I couldn't check infinity on the 90 mm Tele-Elmarit today as it had started to get dark outside. At the same time (after dusk), I also checked my 75 mm Summicron-M APO at the short end, and it seems spot on like the 35 mm and 50 mm lenses.

 

So far it seems adjusting the infinity extreme on the large cam does the trick. Conceptually, I imagine the RF calibration to be a bit like an elastic band with an inhomogeneous tensile profile (i.e. if it's out at the inifity end, it has the effect of non-linearly stretching the calib at the short end). After the adjustment at infinity, the short end seems good (although I'm slightly doubtful with the current observations on the 90 mm Tele-Elmarit).

 

Next step is to put some more film in and run some test test shots at close distances with a wide open aperture. Hopefully the problem is resolved. If not, I'll send off to a pro to calibrate both ends (short and infinity) of the RF.

 

Thanks again to Maarten for the info. This gave me enough to set the infinity end to what I believe to now be good. Now big question is whether the short end is ok (the next roll of film and tests will tell me!).

 

I'm not sure the close end is so easy to adjust.....

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