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I got a Angenieux 12-120mm 10x12A lens, with the silver Bolex H16 RX mount today. I was told it was tested and in excellent condition, but I did come across a problem however: the lens won’t focus at its widest position (12mm). It does focus at some positions like 50mm and I’m wondering what the problem could be? It’s a C mount so it should work on my ACL. Could it be that it just needs to be calibrated and checked, or is there something that I didn’t know and (perhaps) can fix myself?

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When you say it won’t focus at the wide end, what do you mean? Nothing is in focus through the whole focus range? Neither close objects nor distant ones?

Normally if the back-focus setting is off, a zoom will progressively lose focus as you go from telephoto to wide. To keep the image sharp, you would need to shift the focus ring more and more away from the correct distance mark as you zoomed towards the wide end. If nothing at all is in focus at the wide end, the back-focus would have to be way off.

A lens marked RX has been modified slightly to compensate optically for the viewfinder prism in a reflex Bolex, so it’s not ideal for a camera that isn’t a reflex Bolex. The image quality will suffer a little at wide apertures and shorter focal lengths, but it should still focus correctly. 
There may be an issue with the mount not screwing all the way in, or maybe it wasn’t set up correctly.

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6 hours ago, Dom Jaeger said:

Neither close objects nor distant ones?

This. It shifts a little but stays out of focus.

6 hours ago, Dom Jaeger said:

A lens marked RX has been modified slightly to compensate optically for the viewfinder prism in a reflex Bolex, so it’s not ideal for a camera that isn’t a reflex Bolex.

That’s what I was actually afraid of. I asked around and the only thing that people told me was about the viewfinder but not that it changes the image quality. That’s a bummer...

My guess is that either the back-focus is way off or that the mount isn’t set up correctly. Or a combination of both.

Is it worth getting the lens checked and fixed, or would it be too much hassle and not worth it?

 

 

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I wouldn’t worry too much about the RX thing, it’s more of an issue with faster lenses. 

So you can get a focussed image at 50mm, but does it line up with the focus ring marks? And at say 40mm or 30mm can you still get focus? With an object say 6 feet away, where does the focus scale line up at the different settings?

If it is the back-focus, that’s not a difficult adjustment for a technician, but let’s make sure it’s not something else. Can you screw the c mount all the way in? Is it possible something is stopping it from screwing home? 

Have you used other C mounts with the ACL, so that you know the camera is set up correctly?

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10 hours ago, Dom Jaeger said:

Have you used other C mounts with the ACL, so that you know the camera is set up correctly?

Let me start off with something that I forgot to say earlier 😓 My main ACL is currently at Bernie's for a modification so I used another ACL body that I have. Which hasn't been serviced as I don't use it. So maybe it's because of the camera? Although I have to say that I have no problem focussing with my other C mount zoom lens (17-85mm).

10 hours ago, Dom Jaeger said:

So you can get a focussed image at 50mm, but does it line up with the focus ring marks?

No, it lines up between 6 and 7ft.

10 hours ago, Dom Jaeger said:

And at say 40mm or 30mm can you still get focus?

Nope, from 12mm to 30mm is all out of focus. At 40mm it's only in focus when I have it at 5ft. Just a turn with the ring and it shifts out of focus again quickly.

10 hours ago, Dom Jaeger said:

With an object say 6 feet away, where does the focus scale line up at the different settings?

At 5ft. I had the zoom at 120mm. Any other setting was completely out of focus and only at 120mm and 5ft, I had it sharp.

10 hours ago, Dom Jaeger said:

Can you screw the c mount all the way in? Is it possible something is stopping it from screwing home? 

I'm quite sure it's as tight as can be. I feel no resistant whatsoever and when I turn the lens onto the camera mount, it takes as long to turn as it is with my other C mount lenses. 

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2 hours ago, Willem Jansen said:

Let me start off with something that I forgot to say earlier 😓 My main ACL is currently at Bernie's for a modification so I used another ACL body that I have. Which hasn't been serviced as I don't use it. So maybe it's because of the camera? Although I have to say that I have no problem focussing with my other C mount zoom lens (17-85mm).

If another C mount zoom works perfectly on the ACL then it seems the body is OK.

 

2 hours ago, Willem Jansen said:

No, it lines up between 6 and 7ft.

What lines up? What distance is the object in focus? Are you saying that infinity (or a distant object) is sharp when the lens is set to 6-7 ft and the zoom is at 50mm? 

2 hours ago, Willem Jansen said:

Nope, from 12mm to 30mm is all out of focus. At 40mm it's only in focus when I have it at 5ft. Just a turn with the ring and it shifts out of focus again quickly.

So at 40mm you can get infinity to be sharp when the lens is set to 5 ft? But at 120mm, an object at 5 ft is sharp when the lens is set to 5 ft?

If this is the case, then the lens is sitting way too close to the film plane, which means the back-focus needs adjusting. It must be about 2mm out, which is a huge error. It's like it has been set up for a H8RX (the 8mm reflex Bolex), which uses C mount but has a flange depth 2.2mm shorter. Perhaps you should return the lens to the seller, or at least clarify with them how they tested it. 

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6 minutes ago, Dom Jaeger said:

Are you saying that infinity (or a distant object) is sharp when the lens is set to 6-7 ft and the zoom is at 50mm?

Yes. I put the lens in front of a window and measured as far and close as I could.

11 minutes ago, Dom Jaeger said:

So at 40mm you can get infinity to be sharp when the lens is set to 5 ft? But at 120mm, an object at 5 ft is sharp when the lens is set to 5 ft?

Also yes.

I guess I’ll contact the seller as soon as possible because this seems not okay at all.

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Yes, tell them that it seems set up for an 8mm reflex Bolex. I suspect they never "tested" it at all, just played with the rings and decided it felt OK.

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Not really.. sorry.. 12-120s are about the most common old zooms around, so they shouldn’t cost much at all. Newer Angenieuxs like the 9.5-57 or 10-120 are much better but more expensive. I always liked the Canon zooms like 7-63 and 8-64  or the Cooke 9-50 (10.4-52 S16) and 10-30. Zeiss 11-110 is very sharp. All much more than a 12-120 and not c mount either..

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