Question About the Range Finder 'Condenser'

R

ruben

Guest
Fresh morning today, and I started to check my Kiev Range Finder performance according to Rick Oleson's good milk.

I happened to find at the shortest distances 0.9m and 1m, a small caos of disagreement between all concerned parts. According to Rick, there are 2 things to align while ignoring the distance scale: the actual distance between our subject to film plane groundglass, and image coincidence at the range finder viewing window. Both are to be in sharp agreement.

But in my case I happened to find slight differences, bordering my eyesight for the yelow patch sharpness. Fine.

Not fine as I saw myself having to dismantle the whole thing again and my blood pressure increasing. But fortunately at some moment I remembered a small sentence by Peter Tooke, speaking about the condenser's alignment or focusing - I cannot remember exactly.

I am talking about that square optical part, positioned at the left of our camera when it is pointed to a subject. In the past I never gave any importance to this device, but the big holes used to fix it to the main body, left for a kind of alignment, always kept me thinking...

Now when i am spliting hairs in rf alignment for close distances I have found that in my case, by pulling this condenser backwards my rangefinder coincidence improves vis a vis the film plane image. Before long ago, I fully pulled it towards the rf prism pipe.

But I would like to get either comfirmation or denial about this influence, since there are many psycological factors pushing me to accept magical solutions for finaly closing my camera and start using it again.

Cheers,
Ruben
 
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Hi Ruben:

I'm not completely sure that I understand your question, but moving the glass prisms forward or back should not make much difference one way or the other. If you look at the neat animated video in the discussion at http://www.rangefinderforum.com/forums/showthread.php?t=42322 you will see a small black screw head at the right hand end, just above the brass gear. This is where you adjust the coincidence of the rangefinder.... it adjusts by swinging the rear cylindrical element left or right until the rangefinder agrees with the groundglass.

One of the REALLY cool things about that video is that you can see the image of the printed figures moving back and forth, seen through the glass of the rangefinder, as the mechanism moves. This shows very clearly the effect of left-to-right movement of this piece.
 
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Hi Rick,
Yes I didn't explained myself. Let me try another way using this KSS pic:

http://www3.telus.net/public/rpnchbck/shutter assembly removal.html

Here at the first pic on the upper left corner of the Kiev we see the circular outlet of an optical square part, that I happen to call it condenser, without being much sure this is the right designation. Whatever.

I am asking if moving this square part backwards and forwards, as the screw holes enable us, can make a small change in range finder coincidence, as I happened to perceive today. Perhaps it has been a false perception, since the change has been quite small, but good enough for me to be done with the fixing.

Cheers,
Ruben
 
Hi Ruben:

No, that piece is not part of the rangefinder, moving it will not affect the coincidence.
 
Ruben

The word for this is the eyepiece.

I woud have to lift a top and remove to tell you what type it was, there are several generic types of eye piece.

Moving the eyepiece axially should not make a lot of difference since both of the images, the direct view and the rangefinder insert are only seen through parrallel blocks of glass (or a prism) respectively. It may mean that your (glasses) prescription is marginal on the subject you were focusing on. The diopter (power) of the eye piece might change, as it moves closer to your eye.

I'll think about this. I'm not a real optical engineer.

Sorry I did not join in earlier, I was in Se on business, no time for fun, other than falling into Se lake/losing baggage in Copenhagen a/p, eating too much.

Noel
 
Upon Noel clue I have done some "kitchinette" testings and can offer an elaborated answer about the eyepiece function, of interest to us.

The eyepiece square has a small arm to its left, with somewhat big holes for the screws, insinuating an adjustment to be performed.

We can move the eyepiece forwards and backwards, but we can also move it in two angular ways. One is with the left hole closer to us and the right hole farther, and viceversa.

When we play this way, we can notice that the whole image of the viewfinder moves either to the right or to the left, enablilng us to see more of the left side of the subject or of the right side of it. But this is not the issue at all.

If we concentrate instead in what happens within the yellow patch by this angular play, we will find that by playing the angle what we see within the yellow patch area becomes blurer or sharper.

This is the adjustment to be performed. We are not talking about the range finder coincidence but about the sharpness of the the image within the yellow patch area. Do it and you will see it by yourself.

In my case upon improving sharpness I thought the coincidence for close distance was improved. It was not, I just happened to better see the existing coincidence, once the area inside the yellow patch became sharper.

Thanks again to Noel.

Cheers,
Ruben
 
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Ruben

There are three things

The eyepiece needs to be

coaxial, the axis of eye piece needs to point at the axis of the rgfdr optics
centered, similar but different
and close to you eye, the exit pupil of the eye piece will be larger and hence the image brighter in poor light, but if you are old like me then glasses may need to be changed...

You need to ensure all three, within any interference limit from the top plate, which is close to the eyepiece rear.

Noel

If you move the beam splitter you need to redo/check the eyepiece alignment...
 
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Xmas said:
Ruben

There are three things

The eyepiece needs to be

coaxial, the axis of eye piece needs to point at the axis of the rgfdr optics
centered, similar but different
and close to you eye, the exit pupil of the eye piece will be larger and hence the image brighter in poor light, but if you are old like me...
You need to ensure all three, within any limit from the top plate, which is close to the eyepiece rear.

Noel

If you move the beam splitter you need to redo/check the eyepieve alignment...
Click to expand...


OK, let see. All parts I will be talking below refer only to the side of the camera where the viewing window is found.

First the outer side of the beam splitter, and the glass which we clean when our cameras are closed, are not parallel.

The back face/glass of the beamsplitter is almost parallel to the outer face of the beam splitter but not exactly parallel.

The eye piece, after I fixed its position for best sharpness, is fully parallel to the back face/glass of the beam splitter, i.e. (if any one is lost) the back face/glass of the beamsplitter and the eyepiece ARE parallel, and as close as possible, since in order to bring the eyepiece to this parallel situation you must turn it a bit.

But both the back glass of the beamsplitter and the whole eyepiece are not parallel to the general orientation of the camera.

In order to attain its present position, the two screws of the eyepiece arm, are positioned as follows: the screw closer to the eye piece is fully pushed towards the beamsplitter. The farther screw in opposite direction, meaning as close as possible to the human eye. All this means that the eyepiece is in a kind of angle inwards, parallel to the back face/glass of the beamsplitter, and as a whole, as close as possible to the human eye.

Amen

Cheers,
Ruben

I wait for your comfirmation.
 
Ruben

How accurately are you measuring the back and front face of your beam splitter for parallel? Before I measure one of mine?

I said the axis of the eyepiece needs to be coaxial with the axis of the rgfdr, I should have said the axis of the rgfdr stationary/moving lens cum prism system, that is what I ment you to understand sorry, my fault entirely.

If you focus a kiev on a point source and then

- move your eye to left and right
- move the camera so that the point source is at left hand edge and right hand edge of the gold square

Both there effects should show you the sensitivity of the eyepiece position, relative to the prism complex, as well the view through the beam splitter, but the latter will be more difficult to see.

These two movements are not the same as axial movement, or cross axis movement or rotation of the eyepiece, but at least one should demonstrate the syndrome.

Noel
 
Xmas said:
Ruben
How accurately are you measuring the back and front face of your beam splitter for parallel? Before I measure one of mine?
Click to expand...

By simple eye from above, it is fairly easy to see it.


Xmas said:
.........., I should have said the axis of the rgfdr stationary/moving lens cum prism system.......
Click to expand...

What do you mean by "stationary/moving lens cum prism system ?


Xmas said:
..............If you focus a kiev on a point source and then
- move your eye to left and right
- move the camera so that the point source is at left hand edge and right hand edge of the gold square

Both there effects should show you the sensitivity of the eyepiece position, relative to the prism complex, as well the view through the beam splitter, but the latter will be more difficult to see.

These two movements are not the same as axial movement, or cross axis movement or rotation of the eyepiece, but at least one should demonstrate the syndrome.
Click to expand...

I have done it without problem, but what syndrome should I look for ?
 
Ruben

If you focus at the centre of the gold spot for concidence - then the concidence shoud be different at the edges of the spot?

Noel
 
There is a minimum of the minimum, such a minimum that I am not sure if I am indeed seeing it or imaging it.
 
Noel,
You leave me a bit unclear, as I am used to more popular terms. Do you mean to say that the proof of the correct eyepiece AND beamsplitter positioning is in obtaining full sharpness in the center and four corners of the yellow patch ?

For me, by now the issue is very simple: by finding a correct angle when positioning the eye piece, the image within the yellow patch improved. In my specific case that angle has resulted in positioning the eye piece parallel to the rear face/glass of the beam splitter.

The posibility of adjusting forwards, or backwards, or diagonally, the eyepiece is given by its arm having big holes, bigger than the screws width - thus insinuating the possibility of adjustment.

But take into account, in general my eye sight is not the best, my glasses outdated.

Cheers,
Ruben
 
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Ruben

No something different, we are still at cross purposes...

If you do the experiment suggested earlier there should be coincidence at the centre but a displacement at the edges. The sharpness difference should not be detectable unless you have the eyes on an eagle, which you seem to have confessed to.

Instead if you move the eyepiece axially then you will alter the diopter of the system and you may indeed thereby see the image more clearly. If you do this then you will also have to check the rangefinder calibration as you may have disturbed it.

So your maintenance scheme should read, it is recommended to

- move the eyepiece
- check the top plate will still fit, remove the top plate again &
- calibrate the rangefinder at '8' & 0.7m

This is the safe and most careful route.

Noel
 
Xmas said:
Ruben
.............a displacement at the edges. The sharpness difference should not be detectable

Noel
Click to expand...

Ok, now I changed my subject for focusing into several bigger subjects. From the center of the yellow patch, when I move the subject to the right of the yellow patch, then the subject climbs up a bit, and the contrary when I go to the left of the yellow patch.

What this means ?

Cheers,
Ruben
 
Xmas said:
Ruben

No something different, we are still at cross purposes...

If you do the experiment suggested earlier there should be coincidence at the centre but a displacement at the edges. The sharpness difference should not be detectable unless you have the eyes on an eagle, which you seem to have confessed to.

Instead if you move the eyepiece axially then you will alter the diopter of the system and you may indeed thereby see the image more clearly. If you do this then you will also have to check the rangefinder calibration as you may have disturbed it.

So your maintenance scheme should read, it is recommended to

- move the eyepiece
- check the top plate will still fit, remove the top plate again &
- calibrate the rangefinder at '8' & 0.7m

This is the safe and most careful route.

Noel
Click to expand...
Ruben

This means

Your maintenance scheme should read, it is recommended to

- move the eyepiece
- check the top plate will still fit, remove the top plate again &
- calibrate the rangefinder at '8' & 0.7m

The reason is that moving the eyepiece may be similar to looking at the edges of the gold patch.

But now you have me worried as well an I will have to look through my Kiev's and Contax's, sorry will report on this tomorrow...

Noel
 
By your rationale I understand I am going to make you worry further more, but after testing at 1 meter, my rf coincidence fully agrees with my split image OM focusing screen at the film plane.

And both are pretty pretty close to the distance scale.

Why 1 meter instead of 0.9m ? Because I want to live in this world.

Cheers,
Ruben
 
Ruben

That is good. Did you check at '8' as well? The problem only would be bad if the eyepiece is a long way out, and the sequence suggested should compensate. Leitz were reputed to check at 10m as well.

Noel
 
Free service for the neighbourhood: When Noel writes '8', he means infinity.
 
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