infinity focus adjustment on M2 RF

[Justin Low]

>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?

As Andy describes, you can use a piece of paper at the film gate, and a point source of light. Magic tape (the frosted tape sold by 3M) works well too. Just keep the shutter open at B and check focus with a loupe. A check at 1 meter would suffice.

I find it more of a 'confirmation' that the rangefinder is aligned properly. I wouldn't adjust the lens, as that would involve shimming or sanding off to get the distance correct.

You could do it for all your lenses, and it'd be nice to know that they are all focusing at the correct distance. However, if one or more lens should be out, would you adjust the body or those lenses (and with those lenses adjusted, would they work on other bodies?).

 

[Justin Low]

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 😉

Tom, it does take a degree of manual dexterity, but you certainly don't require the skill of a watchmaker.

I admit that it was as you say "intriguing and terrifying" at first, but after practicing on numerous Zorkis or fixed lens rangefinders, it's become quite easy, and fun.

That said, there are some things I prefer to leave to my technician. Things like adjusting the arm length of the RF described above, and tuning the shutter. There's too much trial and error involved and I would rather spend my time more productively.

 

[Andrew3511]

It wasn't that bad doing it and required more patience than dexterity. Having the camera on a tripod is unhelpful and unneccessary, I just put it down on a table on the zero mark of a tape measure and aimed at a target standing on the 1m mark, a matchbox would do very well. I should point out that my starting point was a very doggy M4-P which I knew to have been dropped by me once and by the previous owner at least 2 or three times more judging by the dents. I knew the rangefinder adjustment was well out and reckoned I would lose nothing by having a play with it. The catalyst had been developing a roll of film on which I had taken several pictures with the 75mm Summilux and missed the critical focus point. The collimation wasn't a true collimation of the lens really, more just a visual confirmation that I had got it right with the rangefinder adjustments at the 1m mark. I am pretty sure the lens is OK and haven't any worries about the other lenses I own, so I haven't repeated the exercise for the others.

Collimating a lens is reasonably easy though - set 2 cameras lens to lens, one with a lens known to be correctly focussed at infinity. Both shutters locked open, the distance between the cameras is not important but they need to be accurately aligned facing one another. On the known accurate camera put a piece of tracing paper or translucent tape at the film gate wtih a cross or similar symbol drawn on it in the middle. On the camera you want to adjust you have a similar piece of tape as a focussing screen (or use the normal screen in an SLR) Shine a light from behind the good camera through the tracing paper, focus the image on the camera you are adjusting. bingo, you have correct infinity focus.

Has to be better than watching TV??

 

[AusDLK]

>As Andy describes, you can use a piece of paper at the film gate, and a point
>source of light. Magic tape (the frosted tape sold by 3M) works well too. Just
>keep the shutter open at B and check focus with a loupe. A check at 1 meter
>would suffice.

Jeepers, I just don't get it.

If someone has time for a step-by-step explanation that would be appreciated. Right now, I'm pretty much clueless.

Sounds like the back of the M camera has to be open? Otherwise how can a loupe be used?

Then what happens if it isn't sharp??? Is the lens off or is the camera off? How would I know? Try a different lens?

Sorry to be so hand-holdy but it appears I've bitten off more then I expected.

 

[Andrew3511]

Lens collimation the step-by-step guide: (I should add that I found something very useful on this somewhere on the web but as always, I can't find it again. I was trying to sort out an Olympus Zuiko 200mm at the time so it could be in some Olympus site.)

What you are trying to do is to establish accurate infinity focus for a lens/body combination. The optical physics required is that the projected image from the film plane of a camera + lens set to infinity will focus at the film plane of a second camera/lens when that combination is also set to infinity and pointing lens to lens directly at the first (image) camera. Yes, you need the backs off both cameras and you need the shutters cocked open as well. The frosted tape with something drawn on it and a light behind it acts as the image in the first camera. This is focussed by the second camera. The loupe is to inspect the image on the frosted tape from behind the film plane on the second camera to check it is critically focussed. Most lenses have a grub screw somewhere which sets the infinity point. Loosen that, fiddle around till the image is in critical focus and then retighten the grub screw. A table will do well enough to support the cameras, but the lenses have to be pointing pretty exactly at one another. If all your lenses are off then it's the camera, but that is pretty unlikely unless it has suffered really severe damage or the lens mount has been removed and not replaced correctly. It's not that unusual for a lens to be a little bit out especially if old and mishandled/dropped a few times, the point is only set by small screws, but in the camera it is the lens mount to film plane distance that would have to be out, unlikely.

 

[AusDLK]

Fixed it.

It took a CW turn rather than CCW turn. And coming up through the hole in the base of the camera didn't really work so well. It took a fairly large screwdriver to get the screw to turn -- no way it would fit up through the bottom.

Also getting that darn little cap off and back on was tricky. Who knew that you turn it to free a couple of tabs. I guess this takes a special tool to turn it from inside. Anyway, I got it back on by flattening the tabs back out and turning it with some sticky goop between my finger and the cap.

All of that was unnecessary to actually turn the concentric screw anyway.

But all well that ends well.

 

[gregg]

RFF rocks!

I just got back from an assignment in New Orleans where my M6 was banged around a lot. On the last day I was on top of a building shooting down onto the Superdome when I noticed my RF wouldn't quite go all the way to infinity. Ahhhh! Three days of shooting under my belt and my focus is off...

Now home and found this thread.

Although I still need to soup the film I'm reassured that most of my shots will be OK - checked my close-focus at 1M and it was fine. Adjusted the roller screw CCW just a fraction and the infinity is good now. Re-checked 1M (and .7M) and all is good on close-focus. Whew.

Cheers!