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Help needed to identify enlarging-lens mount (Illumitran)
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PostPosted: Wed May 01, 2013 4:41 pm    Post subject: Help needed to identify enlarging-lens mount (Illumitran) Reply with quote

Hello,

I posted this question in the POTN Canon forum a few days ago and member Gasrocks suggested I post it here (thanks, Gene!).

I'm hoping to digitize my father's slides using my Canon 5DII. So I recently bought a Bowens Illumitran, which came with a Rodagon 60mm f/4 enlarging lens.

My dad shot 54 x 54mm slides (the size of the visible picture area; the mount is 70 x 70mm), and unfortunately it turns out it's not possible to get them in focus with the Rodagon and the 5DII: the body has to be just too far away from the slide, to fit onto the Illumitran.

So, one solution is to buy a shorter lens. Thing is, it has to be the same mount as the Rodagon, so as to fit on the far end of the Illumitran bellows (else I'd need an Illumitran converter, and they're not easy to find in the UK).

I've been looking around on the web for a 40mm enlarging lens but none seem to have the mount I need.

Can anyone tell me what kind of mount it is? In the pic, it's the triangular-section flange round the upper end of the lens, which is held in place on the Illumitrans bellows by a very simple lip plus two retaining screws.



On POTN, several members suggested this mount should to come off to reveal an M39 mount underneath. But it refuses to budge and I'm beginning to wonder if Rodenstock made these specially for Bowens to sell with the Illumitrans.

I don't want to waste too much time looking for a lens that doesn't exist!

(Oh, and any suggestions for another lens would be handy!)

Thanks very much,[img][/img]


PostPosted: Wed May 01, 2013 4:53 pm    Post subject: Reply with quote

Oh heck, I'm sorry - every time I've previewed my post, the picture has been visible - but every time I view it in the thread, it isn't.

What am I doing wrong?

Apologies,

Nick


PostPosted: Wed May 01, 2013 5:03 pm    Post subject: Reply with quote

WannbeTilt wrote:
Oh heck, I'm sorry - every time I've previewed my post, the picture has been visible - but every time I view it in the thread, it isn't.

What am I doing wrong?

Apologies,

Nick


I think it is an antispam measure. Your first post can't contain an image.


PostPosted: Wed May 01, 2013 5:14 pm    Post subject: Reply with quote

Oh, thank you - that makes sense!

It's showing now, anyway.

Nick


PostPosted: Wed May 01, 2013 5:42 pm    Post subject: Reply with quote

There is the retaining ring visible under that dovetail part, so it certainly has a M39 thread mount underneath.


PostPosted: Wed May 01, 2013 6:07 pm    Post subject: Reply with quote

I agree, the retaining ring is a dead giveaway that the adapter is removable.

BUT...

Be careful when you try to remove it that you don't put too much torque on the aperture adjusting ring. Pushing them too hard can cause the aperture leaves to come out of alignment, or even to bend and be damaged forever. Hold the lens by some other part, or if that doesn't work disassemble the lens to make the body easier to grab hold of.


PostPosted: Wed May 01, 2013 6:29 pm    Post subject: Reply with quote

Ray Parkhurst wrote:
I agree, the retaining ring is a dead giveaway that the adapter is removable.

BUT...

Be careful when you try to remove it that you don't put too much torque on the aperture adjusting ring. Pushing them too hard can cause the aperture leaves to come out of alignment, or even to bend and be damaged forever. Hold the lens by some other part, or if that doesn't work disassemble the lens to make the body easier to grab hold of.


Thanks - I've tried, and I assure you it's impossible. The lens body is very small, so there's little to grip except the aperture ring. This actually moves out of 'click' position anyway. Perhaps the adapter has become bonded to the lens with age (though there's no sign of corrosion). I'm loath to squirt WD40 down there - or maybe I should?

Nick


PostPosted: Wed May 01, 2013 6:45 pm    Post subject: Reply with quote

Sure, a few drops of WD40 and some mild heat using a hair dryer should help.
Be patient, WD40 may take several hours to loosen that up.


PostPosted: Wed May 01, 2013 6:57 pm    Post subject: Reply with quote

Bare aluminum in contact with aluminum can become "welded".
I have a couple of cases of this. Sometimes the condition is hopeless, sadly.

Heat is a good idea. Be careful as this has a risk of cracking a lens. Increase and decrease the temperature slowly.

Also a shock, such as a strong tap from a hammer in the direction of the thread. You have to be very careful with that of course.


PostPosted: Wed May 01, 2013 9:25 pm    Post subject: Reply with quote

OK, thanks again everyone for taking the trouble to read this thread and share advice, much appreciated!

Nick


PostPosted: Wed May 01, 2013 10:15 pm    Post subject: Reply with quote



I presume you just want to remove this part ?

Place the lens in a small plastic bag, or better still a condom, something waterproof. Then get a pan of very hot water and lower the lens in just enough to cover the mount ring, let the heat transfer into the ring, maybe 15 seconds, then remove quickly, get it out of the bag and try to unscrew the ring.
This has worked for me when I found a T2 ring that was so tight I couldn't shift it, it came off easily.


PostPosted: Thu May 02, 2013 12:20 am    Post subject: Reply with quote

It's definitely M39, I had one of these. BTW, it's not an enlarging lens, it's a printing/repro lens, you can tell by the different barrel design - the red line is the key identifier, although the whole barrel is different to the enlarging Rodagons. I think the only different between these and the enlarging ones is the magnification ratio they are optimised for - the enlarging ones are for small magnifications, these are for higher ones.


PostPosted: Thu May 02, 2013 8:08 am    Post subject: Reply with quote

I was going to suggest a method I have used in the past, cutting the offending adapter most of the way to the threads with a hacksaw in two opposing places, thereby nearly cutting the adapter in half, and then flexing the halves with pliers until they break apart. But then I thought to suggest you see if the diameter of the adapter is somehow useful. First thought is if it possibly might fit in a T-mount adapter? The 3-screw kind. What is the outer diameter?

Ray


PostPosted: Thu May 02, 2013 9:20 am    Post subject: Reply with quote

iangreenhalgh1 wrote:
It's definitely M39, I had one of these. BTW, it's not an enlarging lens, it's a printing/repro lens, you can tell by the different barrel design - the red line is the key identifier, although the whole barrel is different to the enlarging Rodagons. I think the only different between these and the enlarging ones is the magnification ratio they are optimised for - the enlarging ones are for small magnifications, these are for higher ones.


You couldn't be more wrong. It's a simple enlarging lens, a bit newer model that the earlier zebra types, a bit older than the more modern style. That's the only difference. But just for clarification, doesn't contribute anything helpful to the OP's question...


PostPosted: Thu May 02, 2013 11:34 am    Post subject: Reply with quote

Lloydy wrote:
I presume you just want to remove this part ?

Place the lens in a small plastic bag, or better still a condom, something waterproof. Then get a pan of very hot water and lower the lens in just enough to cover the mount ring, let the heat transfer into the ring, maybe 15 seconds, then remove quickly, get it out of the bag and try to unscrew the ring.
This has worked for me when I found a T2 ring that was so tight I couldn't shift it, it came off easily.


Goodness, that's a radical and interesting idea, thank you! Since I've been into lenses, I've had no use for my condoms! Laughing

Ray Parkhurst wrote:
I was going to suggest a method I have used in the past, cutting the offending adapter most of the way to the threads with a hacksaw in two opposing places, thereby nearly cutting the adapter in half, and then flexing the halves with pliers until they break apart. But then I thought to suggest you see if the diameter of the adapter is somehow useful. First thought is if it possibly might fit in a T-mount adapter? The 3-screw kind. What is the outer diameter?

Ray


The flangey bit measures exactly 5 cm across. It does have a screw thread in the inside, and the inner diameter is 3.9 cm - so does that confirm it's M39 underneath?

Thanks again,


PostPosted: Thu May 02, 2013 11:52 am    Post subject: Reply with quote

luisalegria wrote:
Bare aluminum in contact with aluminum can become "welded".
I have a couple of cases of this. Sometimes the condition is hopeless, sadly.

Heat is a good idea. Be careful as this has a risk of cracking a lens. Increase and decrease the temperature slowly.

Also a shock, such as a strong tap from a hammer in the direction of the thread. You have to be very careful with that of course.


Louis wanted to say - I'm sure about that - that you had to use a dead blow hammer not a metal one.


PostPosted: Thu May 02, 2013 12:35 pm    Post subject: Reply with quote

Himself wrote:
Louis wanted to say - I'm sure about that - that you had to use a dead blow hammer not a metal one.


Thank you - bashing and heating is slightly outside my comfort zone but I'll give one of these methods a go, if I don't find the right lens!

Best wishes,


PostPosted: Thu May 02, 2013 2:42 pm    Post subject: Reply with quote

WannbeTilt wrote:
Lloydy wrote:
I presume you just want to remove this part ?

Place the lens in a small plastic bag, or better still a condom, something waterproof. Then get a pan of very hot water and lower the lens in just enough to cover the mount ring, let the heat transfer into the ring, maybe 15 seconds, then remove quickly, get it out of the bag and try to unscrew the ring.
This has worked for me when I found a T2 ring that was so tight I couldn't shift it, it came off easily.


Goodness, that's a radical and interesting idea, thank you! Since I've been into lenses, I've had no use for my condoms! Laughing

Ray Parkhurst wrote:
I was going to suggest a method I have used in the past, cutting the offending adapter most of the way to the threads with a hacksaw in two opposing places, thereby nearly cutting the adapter in half, and then flexing the halves with pliers until they break apart. But then I thought to suggest you see if the diameter of the adapter is somehow useful. First thought is if it possibly might fit in a T-mount adapter? The 3-screw kind. What is the outer diameter?

Ray


The flangey bit measures exactly 5 cm across. It does have a screw thread in the inside, and the inner diameter is 3.9 cm - so does that confirm it's M39 underneath?

Thanks again,


Yes, that seems to be further confirmation.

The 50mm diameter is also telling. I checked a couple of my T-mount adapters, and some are 49mm while some are 50mm. It may be that what you have there is the remnants of an adapter that froze up and for some reason the outer piece was removed. Or, the mount that this went to used a similar notched adapter. I think you might have some luck with this. What camera mount are you trying to put this on? Perhaps purchase a T-mount adapter for that mount and then swap out the T-mount portion with the one fused to your lens?

I don't know which brands are 49mm and which are 50mm, and there may be other diameters as there was no standard I know of. You may need to use trial and error. Or, if you end up with a 49mm, you might have to grind/file the outer diameter down by 1mm to make it fit...


PostPosted: Thu May 02, 2013 5:27 pm    Post subject: Reply with quote

Ray Parkhurst wrote:
Yes, that seems to be further confirmation.

The 50mm diameter is also telling. I checked a couple of my T-mount adapters, and some are 49mm while some are 50mm. It may be that what you have there is the remnants of an adapter that froze up and for some reason the outer piece was removed. Or, the mount that this went to used a similar notched adapter. I think you might have some luck with this. What camera mount are you trying to put this on? Perhaps purchase a T-mount adapter for that mount and then swap out the T-mount portion with the one fused to your lens?


My guess is, this adapter was only for mounting this kind of lens on a Bowens Illumitran. Illumitrans often seem to come with a 50mm or 60mm Rodagon. Unless I can find a spare adapter, or another lens with one already attached, I'll have to wrestle the darn thing off, so I can use it to mount a shorter, wider enlarging lens on the Illumitrans with my 5DII!

Nick


PostPosted: Thu May 02, 2013 6:37 pm    Post subject: Reply with quote

WannbeTilt wrote:
Ray Parkhurst wrote:
Yes, that seems to be further confirmation.

The 50mm diameter is also telling. I checked a couple of my T-mount adapters, and some are 49mm while some are 50mm. It may be that what you have there is the remnants of an adapter that froze up and for some reason the outer piece was removed. Or, the mount that this went to used a similar notched adapter. I think you might have some luck with this. What camera mount are you trying to put this on? Perhaps purchase a T-mount adapter for that mount and then swap out the T-mount portion with the one fused to your lens?


My guess is, this adapter was only for mounting this kind of lens on a Bowens Illumitran. Illumitrans often seem to come with a 50mm or 60mm Rodagon. Unless I can find a spare adapter, or another lens with one already attached, I'll have to wrestle the darn thing off, so I can use it to mount a shorter, wider enlarging lens on the Illumitrans with my 5DII!

Nick


In that case, the only safe way I know is to remove the lens elements and the aperture ring, then use one of the suggested techniques, or a pair of rubber wrenches, or a circular vise attachment, etc. Penetrating oil, heating of the adapter, etc all may work. Good luck and let us know how it comes out!