Focusing problem: Schneider-Kreuznach 90mm f6.8 Angulon

[igor_smirnoff]

I've just picked it up on Ebay and although the lens looks good I can't seem to be able to focus it.

 

In fact, it does not create anything similar to an image at all regardless of the distance from the ground glass. The

light circle it forms reminds that of a condernser lens - a flat even circle.

 

Without the front element, though, the lens focuses all right with the focal range of about 150mm. Is there anything I

am missing? I feel like an idiot because there seems nothing wrong with the lens. The pitures are here:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=280249338294&ssPageName=STRK:MEWN:IT&ih=018

 

Any suggestions will be appreciated. Thank you!

 

Igor

[jonathan_bourla1]

Hi. Just a quick question. Can you camera focus down to 90mm with your camera as it is? (what camera do you have?). Some might

need a bag bellows or a recessed lens board, and maybe your camera physically can't focus a short lens like this without, say, a recessed

board or some clever arrangement of the front standard (to bring the lens closer to the ground glass and film).

 

Jonathan

[tim_ludwig2]

Igor,

 

I hope I don't insult your intelligence, but I have no idea of your experience level or of the camera you are mounting

this lens on.

 

 

It is possible that one or more of the elements are out of their proper position in the front group or altogether

missing. If so, send it back for the refund they guarantee because this repair could get expensive.

 

This is obviously a wide angle and will sit far back on the camera's focussing rail in order to focus at infinity. If your

camera bellows cannot compress enough, that could put you in a position of only being able to focus on much more

close up images. (One of my old cameras, a Korona 4x5 will not focus with a 90mm because of it's construction.)

 

In the daylight, but in a darkened room, either take a piece of thin (translucent) white paper or get close to a white

wall that is across from a window with a bright outside view. Hold just the lens (no camera) and move it in and out

while looking for an image to form on the wall or on the paper while you are looking at it (the paper) from behind. If

the image comes into focus of the outdoor scene which will effectively be at infinity, the lens is fine and you've got a

problem with how it compresses into the camera. If it does not focus, send it back.

 

These lenses would work on an old Crown or Speed Graphic with only the bellows provided, so I'm betting on a real

problem with the lens. However, if you do get it to focus in the test, you may need a different camera that can take a

bag or wide angle type of bellows

 

What camera are you tring to mount this on?

 

Good luck.

 

Tim

[igor_smirnoff]

Thank you for the quick replies, guys. I think I have figured it out.

 

It appears that its front group consists of only 1 element instead of 3! as shown ->

http://www.schneider-kreuznach.com/archiv/pdf/an_su_1963.pdf

 

Apparently there was lens separation at some point (it's an old timer!) and the owner just screwed back the frontal

part with the remaining piece on it. It looks OK from the outside.

 

It's no big deal for me, rather a good reminder to check everything that comes from EBAY!

[jonathan_bourla1]

Hi again. I'm pleased you've worked out what was wrong, but I think you should get back in touch with the seller. They

probably weren't aware of the issue, but say they pride themselves on customer service, so it's probably worth a try at

getting a refund. Good luck.

 

Jonathan

[scott_kathe1]

Try the lens wide open in a darkened room and aim it at a lighted room at night. Hold the lens so that it projects the image onto a white wall or a stiff sheet of paper. Move the lens back and forth and I bet you will see your upside down reversed image. The 3 cemented elements in the front group look like one element-at least they did on mine. I find it hard to believe that it lost an element or two and there isn't any residual balsam. I know there are dishonest people out there but...

 

Scott

[ole_tjugen]

I've got one of those too - but I knew it was bad and bought it as a spare rear cell!

 

Only the outer element of each cell is fixed to the barrel; the two inner elements of each cell are only held by the cement to the outer element. This leads to a risk of "slippage" if the lenses are stored "on edge" in high temperatures, and that sometimes (say, if dropped too many times) the inner elements may simply drop off.

 

The slippage is worse since it's impossible to detect without using the lens: Decentered elements leads to very poor definition, possibly the reason why Angulons are so variable in quality.

[ole_tjugen]

PS: I looked at the pictures in the auction, and it's obvious to me that the inner two elements of the front cell are missing. But it's only obvious if you know what that looks like, so it's possible that the seller was unaware.