infinity focus adjustment on M2 RF

[AusDLK]

Has info on how to do this adjustment ever been posted here on RFf?

Mine focuses "past infinity". Over focus? (Not sure of the correct terminology.)

I'd like to not have to ship if off the DAG again (Don just installed the M2 rangefinder in my M3) if this is simple adjustment that I can learn to do myself.

Anyone? Anyone?

 

[Branestawm]

Setting infinity on an M is a bit awkward. The adjustment is made by turning the slotted screw head in the centre of the cam follower roller which is on an eccentric. I made a right angled screwdriver up to do this but it's a process of trial and error since the lens has to come off to do the setting. The other problem is that as you turn the eccentric the effective length of the rangefinder arm changes so that altering the infinity setting effects the close focus accuracy as well. The securing screw of the arm also has an eccentric adjustment for setting it's length but moving this tends to upset the infinity point so you end going round in circles until both infinity and close focus are correct. I seem to remember seeing a link to an M service manual on rff but I can't remember where. Maybe someone could provide a link.

Paul

 

[john neal]

Dave,

As Paul said, this is a frustrating exercise that needs to be checked at inf and 1 metre to get a good result.

There are some tips that i sahred with the RFF community hosted on Kim Coxon's website at http://www.pentax-manuals.com/repairs.htm, that may be what Paul was referring to.

I'm not sure this is something I would want to be doing myself.

 

[Justin Low]

Just my two cents: you can make small adjustments to infinity by turning the screw where the RF roller is.

You can fashion your own right angle screwdriver, but another way to access the screw is through a hole in the bottom of the chamber. Remove the plate with the loading diagram and you'll be able to pop the hole cover out. This way you can use a regular screwdriver, and it's less finicky.

You can adjust the vertical alignment by removing the screw next to the frameline illumination window. There will be a screw within. If you have a lens mounted, it is easier to see and reach the screw when focused to closest distance.

Only minute turns are needed, and apply only a turning force, don't press down. Check focusing at one meter, three meters and infinity.

If you need pictures to illustrate the procedure, let me know.

 

[AusDLK]

I tested the infinity focus with a VC 35mm Nokton and a ZI 50mm Sonnar and they seem to be off by the same amount so I'm confident that it is the camera that is off.

It sounds like it is not necessary to remove the top plate to make these adjustments which is good news.

And if anyone has any diagrams regarding these procedures that they can share that would be swell.

 

[AusDLK]

One more thing...

What kind/size of screwdriver are we talking about?

 

[Ronald M]

A screwdriver that fills the slot but is not too small.

It is difficult to rotate, but do not push up too hard, just twist.

Set it for a star on a good night or just short of infinity across the street for a temporary patch.

Then check 1 meter from the film plane. If this is off, send it out. This adjustment is more difficult, but not usually necessary.

 

[Justin Low]

I hope these pictures help.

The first picture shows all the parts after you have remove the base cover. First remove the three screws on the cover and lift off. Remove the long metal strip (this is what the baseplate locks to). Look into the hole where the screwdriver has been inserted, and you will see the bottom of the port cover. Insert a screwdriver and twist the lock and the cover will come off.

Second picture shows a detail of the operation. Insert a screwdriver through the access port, and you will be able to reach the indicated screw. Apply turning force only and do not push against the arm.

Reassembly is the reverse. I.e replace the port cover, replace the metal strip, and screw on the base cover.

Do note that my M2 is a relatively early sample. Later M models are easier in that the hole which you insert the screwdriver through is much larger.

 

[AusDLK]

Thanks a million for the pics.

My camera is a very early M3. I have film in the camera now so cannot take off the bottom plate but I see the port cover inside the lens mount.

So to make sure I am turning the screw in the center of the larger cam roller, right?

Are you able to say which direction (ie., cw or ccw) to turn the screw to correct the over focus problem that I am experiencing?

 

[Justin Low]

Dave, that's correct. The screw in the center of the roller. I can't remember which way to turn.

 

[Ken Ford]

The screw is actually an eccentric - 360 degrees gets you back where you started, and 180 degrees will be the maximum change. Simply turn it a small amount to see which way you need to go. We're usually talking very small amounts here - if it were me, more than 45 degrees or so would make me want to send it in for service because something else probably changed.

 

[AusDLK]

I bounced this off of Don at DAG and he told me to turn ccw to move the focus toward infinity.

 

[Andrew3511]

Justin, thank you so much. The pictures make all the difference. I have just had my M4-P in pieces all over the dining table with a metre rule and have successfully got an accurate calibration on the rangefinder at 1m and infinity at last! Finishing off with checking the collimation on the 75mm Summilux with an LED flashlight and a bit of thin paper in the film gate and it all works - really isnt so complicated after all. The other adjustment that is on an eccentric is the little stop on the rangefinder. Mine was out so that once I had actually got the rangefinder adjusted correctly the roller hit the stop before the lens got to the infinity setting. Now I have done that there is no more excuse for out-of-focus shots

It really makes me admire the engineering in the camera. You can get at all the bits you need to adjust the rangefinder in both planes by removing just 4 screws in all and the adjustments are both neat and accurate, even if a bit fiddly.

 

[Ororaro]

Andy,

can you elaborate on the 4 screws ? I only know about 2.

Thanks,

Roland.

Yes, please!

I have an M4-P and I'm astounded at all the quick inaccurate information flying on the web.

What are the other 2 screws?

 

[Justin Low]

Hmm. I'm guessing, but Andy could be referring to two things: first, the number of screws to remove to access the adjustment screws (three on the base cover, one on the top plate for the vertical alignment); second, vertical and horizontal alignment, plus the two screws on the rangefinder arm.

 

[Andrew3511]

I had to remove 3 screws on the bottom plate cover to get at the port and the one on the front of the top plate to adjust the vertical alignment. I had attempted to find a right-angled screwdriver before Justin posted the pictures of taking off the plate and accessing the hole, but you can't find one small enough to get through the throat of the camera and do the business. Once the screw on the rangefinder arm pivot is loosened there is an eccentric washer beneath with a small slot in it. Push one way and the arm with the roller gets longer, the other it gets shorter. This adjusts the rangefinder at 1m. However, the procedure referred to elsewhere (& which worked for me in practice) was to initially sort out the infinity adjustment, then adjust the 1m. This threw out the infinity, so I then went back and readjusted this (as the 1m was a long way out). Finally did a fine tune on the 1m, then final check on infinity. Last check was against lens collimation at 1m with point source and paper over film gate and shutter open on B.

HTH

Andrew

 

[AusDLK]

I am becoming confused again.

I've got a handle on how to take the camera apart (ie. the four screws, etc.) but specifically how to adjust the 1m vs. infinity focus and now "lens collimination" has muddied the water.

Specifically -- I've understood that there is a screw and eccentric on the large (fontmost) roller of the RF arm and it is here that the infinity adjustment is done. Can reader(s) confirm this.

But I am less clear on the 1m adjustment. I sounds like this is done using another screw on another part of the RF arm. Where? On the "elbow" of the arm or the base? Do pics iexist showing the different points of adjustment?

It also sounds like the infinity and 1m adjustments should be independent of each other -- but this is not always the case. Is this accurate? Which should be done first?

Next, what does "lens collimination" do? What is the complete procedure? Is it necessary for all lens in my collection? If not, is it better to use one lens (ie. focal length) over another?

Finally, does it make sense to do any of these adjustments with the camera on a tripod and lens on the camera? It seems like it could reduce trial and error attempts. Possible or dumb idea?

 

[Justin Low]

Specifically -- I've understood that there is a screw and eccentric on the large (fontmost) roller of the RF arm and it is here that the infinity adjustment is done. Can reader(s) confirm this.

Correct.

But I am less clear on the 1m adjustment. I sounds like this is done using another screw on another part of the RF arm. Where? On the "elbow" of the arm or the base? Do pics iexist showing the different points of adjustment?

Adjust the length of the arm. I don't have pictures, but it's under the screw at the pivot point, not the limiter.

It also sounds like the infinity and 1m adjustments should be independent of each other -- but this is not always the case. Is this accurate? Which should be done first?

Infinity first. Then check 10 meters and 1 meter. In most cases, it's unlikely you will need to adjust the arm length.

Next, what does "lens collimination" do? What is the complete procedure? Is it necessary for all lens in my collection? If not, is it better to use one lens (ie. focal length) over another?

You are essentially calibrating the lens, such that the focus point at the film plane matches the focus point in the rangefinder.

Finally, does it make sense to do any of these adjustments with the camera on a tripod and lens on the camera? It seems like it could reduce trial and error attempts. Possible or dumb idea?

It's doable I guess. Personally I do not use a tripod as it'd be too tedious to mount and unmount. I'd just place the camera on the table with a tape measure to gauge 1 meter. For infinity, either point the camera out the window, or use an infinity target.

 

[AusDLK]

>You are essentially calibrating the lens, such that the focus point at the
>film plane matches the focus point in the rangefinder.

Okay but what is the procedure?

And is this necessary for each lens that might be used on the camera?

 

[Flyfisher Tom]

These DIY threads are always both intriguing and terrifying at the same time, probably because I don't have the dexterity of a watch maker 😉