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Xenar 135mm F4.5 lens - What's wrong with it?
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PostPosted: Fri Aug 12, 2011 4:29 pm    Post subject: Xenar 135mm F4.5 lens - What's wrong with it? Reply with quote
I bought this old camera made by Schneider Kreuznach for about 30€.
Shutter speed and everything else is working correctly.





But the lens isn't projecting any pictures onto the film.
And here's a comparision with the smaller Voigtar 105mm F3.5


(the left is the Voigtar, this distances of both cameras are the same)




Removing both front elements.






Rear, middle and rront element.
There seems to be only one possibilty to screw them together.

What's the problem? Is an element missing? Question Question

Last edited by ForenSeil on Mon Aug 15, 2011 1:45 am; edited 1 time in total


PostPosted: Fri Aug 12, 2011 6:18 pm    Post subject: Reply with quote
Have you tried a piece of grease proof paper in place of the film back to check there is no image?


PostPosted: Fri Aug 12, 2011 6:48 pm    Post subject: Reply with quote
martyn_bannister wrote:
Have you tried a piece of grease proof paper in place of the film back to check there is no image?


No, but I tried to use my NEX-3 without lens. Does not work.
On my Bessa it works.

When you look with your eyes through this Xenar everything is sharp and distorted while when I look through any other lens I know it's very unsharp or the picture is at least overhead.


PostPosted: Sat Aug 13, 2011 6:55 am    Post subject: Reply with quote
ForenSeil wrote:
martyn_bannister wrote:
Have you tried a piece of grease proof paper in place of the film back to check there is no image?


No, but I tried to use my NEX-3 without lens. Does not work.
On my Bessa it works.

When you look with your eyes through this Xenar everything is sharp and distorted while when I look through any other lens I know it's very unsharp or the picture is at least overhead.

What's the focal length on the one that "works"? This one that doesn't work is 135mm? I'm just thinking it all seems genuine, so it must be pilot error. Or, as you say, a missing element?


PostPosted: Sat Aug 13, 2011 8:51 am    Post subject: Re: Xenar 135mm F4.5 lens - What's wrong with it? Reply with quote



This picture confuses me. You say the lens on the right is the Xenar. Clearly, this lens is producing an image. What surprises me is that the Voigtar on the left does not produce an image. How close to the lens where you to take these pictures? Closer than the lens focal length?

Hold any lens in front of you at arm's length. Point it at an object ( a tree for example). As long as the distance to your eye is greater than the focal length (likely if you are holding it at arm's length) you should see an inverted (up-side down) image of the tree.

If you see an inverted image, the lens is "working" and you should be able to capture the image. If the image is poor quality, an element is missing or in the wrong place (reversed or the distance is incorrect). (Or the lens is just not very good!)

If the image looks good, there may still be a problem with the lens. From the pictures, it looks like the middle element is concave and so a negative element. This will increase the focal length of the first element, but the spacing to the first element is critical. I suspect there might be a missing spacer in this lens that means the focal length is longer than the maximum distance you can position the lens relative to the film plane. The lens will only be able to produce a "virtual" image i.e. an image that is not real and so cannot be captured on a screen (like the image in a plane mirror). (However, this explanation does not fit in with the picture above, hence my confusion)

Try holding the front element in front of the others at different distances to see if it will from an image.

Mark


PostPosted: Sat Aug 13, 2011 9:00 am    Post subject: Reply with quote
Another thought. Maybe the problem is making the focal length of the lens very small, so it will only focus on something very close to the lens. Will it work in macro mode?

Mark


PostPosted: Sun Aug 14, 2011 4:06 pm    Post subject: Re: Xenar 135mm F4.5 lens - What's wrong with it? Reply with quote
Thx for all answers!
martyn_bannister wrote:


What's the focal length on the one that "works"? This one that doesn't work is 135mm? I'm just thinking it all seems genuine, so it must be pilot error. Or, as you say, a missing element?

The focal length of the Voigtar is 105mm.
SXR_Mark wrote:



This picture confuses me. You say the lens on the right is the Xenar. Clearly, this lens is producing an image. What surprises me is that the Voigtar on the left does not produce an image. How close to the lens where you to take these pictures? Closer than the lens focal length?

I was more than 30cm away. The Xenar isn't producing a picture. It's just like looking through a bottom of a bottle.

Quote:
Hold any lens in front of you at arm's length. Point it at an object ( a tree for example). As long as the distance to your eye is greater than the focal length (likely if you are holding it at arm's length) you should see an inverted (up-side down) image of the tree.
If you see an inverted image, the lens is "working" and you should be able to capture the image. If the image is poor quality, an element is missing or in the wrong place (reversed or the distance is incorrect). (Or the lens is just not very good!)

It's not working with the Xenar. I can see a distorted but sharp picture through it from any distance but it's not up-side down inverted.

Quote:
If the image looks good, there may still be a problem with the lens. From the pictures, it looks like the middle element is concave and so a negative element. This will increase the focal length of the first element, but the spacing to the first element is critical. I suspect there might be a missing spacer in this lens that means the focal length is longer than the maximum distance you can position the lens relative to the film plane. The lens will only be able to produce a "virtual" image i.e. an image that is not real and so cannot be captured on a screen (like the image in a plane mirror). (However, this explanation does not fit in with the picture above, hence my confusion)

The lens consists or 3 elements and there's only one way to screw them together so yes, I guess a spacer or another element is missing.

Quote:
Try holding the front element in front of the others at different distances to see if it will from an image.

I've tried it. It's not possible to get any picture with it.

SXR_Mark wrote:
Another thought. Maybe the problem is making the focal length of the lens very small, so it will only focus on something very close to the lens. Will it work in macro mode?

Mark

I also tried to focus very close objects, but without succes.

Sad I think I have to throw this lens in a trash-can.

Last edited by ForenSeil on Sun Aug 14, 2011 4:21 pm; edited 3 times in total


PostPosted: Sun Aug 14, 2011 6:45 pm    Post subject: Reply with quote
Dont throw it away ! Sell it.

The lens is probably recoverable.
The shutter is also very useful. These are really easy to fix also.
And valuable for parts.

And the camera looks like its in fine shape.


PostPosted: Sun Aug 14, 2011 6:50 pm    Post subject: Reply with quote
luisalegria wrote:
Dont throw it away ! Sell it.

The lens is probably recoverable.
The shutter is also very useful. These are really easy to fix also.
And valuable for parts.

And the camera looks like its in fine shape.


Ditto


PostPosted: Sun Aug 14, 2011 7:07 pm    Post subject: Reply with quote
I will vote for reversed lens element(s). Probably in rear holder. Remove lens element from holder, flip it over, re-install into holder, voila?


PostPosted: Sun Aug 14, 2011 7:30 pm    Post subject: Reply with quote
I saw this @ Camera Ecentric-



I am curious if your missing the 4th element on the rear the concave element?Larger images of the cells & elements would be beneficial- Very Happy


PostPosted: Mon Aug 15, 2011 1:28 am    Post subject: Reply with quote
Thank you very much! That's exactly what I hoped for.

Something is wrong with the rear element of my Xenar.

The front of the rear element seems to be concave - but in the drawing it is plane.

I will have a closer look tomorrow


PostPosted: Mon Aug 15, 2011 2:01 am    Post subject: Reply with quote
No, according to that drawing the rear of the front pair is concave, what you have there when you remove the front and back half is the front two elements in the front piece and the rear two elements in the rear piece.

Not that I have taken a Xenar apart, but it's a Tessar clone and I have taken apart a few Tessar types.



If any of the elements are reversed, it will be the rear one of the front group, take it out and see if the deeper concave face is facing to the rear, if not, it's the wrong way round.

The rear group is a cemented doublet, I doubt it can be reversed.

I'm still not convinced there is anything wrong with this lens. Have you measured the distance from the rear element to the film plane in this old camera? You will need to mount it the same distance from the sensor on a digicam, closer and you will never get anything but a super soft image.
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